The Autecology of Eudiaptomus cf drieschi (Poppe & Mrazek 1895 ...

The Autecology of Eudiaptomus cf drieschi (Poppe & Mrazek 1895) 

(Copepoda, Calanoida) in Lake Kinneret, Israel 

Thesis submitted for the degree of Doctor of Philosophy 

Bonnie Rochelle Azoulay. 

Submitted to the senate of 

The Hebrew University of Jerusalem 

November, 2001.

This thesis was completed under the supervision of 

Professor F. D. Por 

Dept. Evolution, Systematics and Ecology,The Hebrew University of Jerusalem 

Professor Moshe Gophen 

The Yigal Allon Kinneret Limnological Laboratory. 

Israel Oceanographic & Limnological Research Ltd.

Table of Contents 

Page 

Abstract 

Research Objectives 1 

1. Introduction 2-8 

1.1 Lake Kinneret Background 2-5 

Biota 3 

1.2 Long-term changes in the Kinneret Ecosystem 5-6 

Biological 5 

Physical 6 

1.3 Previous Diaptomid Data from Lake Kinneret and Israel 6-8 

2. Material and Methods 9-19 

2.1 Seasonal Abundance 10 

2.2 Benthic Resting eggs 10-12 

2.3 Diel Survey 12-13 

2.4 Experimental studies 14-16 

2.4.1 Development 14 

Biometrics 14 

Stock preparation 15 

2.4.2 Data analysis 16-17 

2.4.3 Salinity tolerance 18 

2.4.4 Food requirements 19 

3. Results 20-44 

3.1 General Taxonomy 20-22 

Description of E. drieschi from Kinneret 21-24 

3.2 Seasonal distribution 24-31 

3.3 Sex ratios 32 

3.4 Vertical distribution 32-34 

3.5 Resting egg distribution 34-36 

3.6 Development 38-41 

Development Time 39 

Development and growth rate 40-42

3.7 Salinity tolerance 43-44 

3.8 Food requirements 44 

4. Discussion 45-59 

4.1 Taxonomical Position 45-46 

Biometrics 46 

4.2 Ecological implications of development 47-49 

P/B Ratio 49-50 

4.3 Ecological Role of resting eggs 50-53 

4.4 Vertical distribution 53-55 

4.5 Experimental studies 55-59 

4.5.1 Salinity 55-56 

4.5.2 Temperature 56-58 

4.5.3 Food 58-59 

5 Conclusions 60-63 

6 References 67-77 

7 Appendix 78 

A 1. Abstract of conference presentation 

Hebrew Summary

Abstract 

Prior to the mid-eighties, diaptomid copepods were only “accidental visitors” in 

Lake Kinneret. Early surveys reported sporadic appearances of diaptomids in the littoral, 

especially after winter floods, but not from other regions. Samples collected after 1986 

showed the presence of the diaptomid Eudiaptomus drieschi (Poppe & Marzek 1895) 

throughout the pelagic regions of the lake. This is the first record of 

E. drieschi outside of its previous range, as well as the first report of a diaptomid species 

invading Lake Kinneret. It had been previously recorded from Sri Lanka, Yugoslavia, 

Greece, and Turkey. Records of the population were begun in 1994. Population densities 

and life history parameters of this organism have been monitored from a fixed sampling 

site, (Station F, 20 m depth) in the northwest region of the lake (this study) from 1996. 

E. drieschi does not appear to produce identifiable cohorts, but reproduces 

continuously throughout the time it is present in the water column. In order to obtain 

production and biomass estimates, growth and development were measured in the lab. 

Individuals were reared at different temperatures and salinity. Duration of stage 

development and growth increments were measured. Results indicate that temperatures 

> 24 0 C are lethal to Eudiaptomus, and in chloride concentrations 

> 250 ppm, this organism does not develop naturally. 

A number of noticeable biological and chemical changes have occurred in Lake 

Kinneret since 1969. The diversity of the pelagic zooplankton has increased, with 

formerly rare individuals; Chydorus sphaericus (By Birge), Moina rectirostris (Leydig) 

appearing more frequently. Also, Conchiloides sp., a colonial rotifer and, Anuraeopsis 

fissa (Gosse), a brachionid, are found seasonally in plankton samples. Long – term 

records also indicate changes in phytoplankton biomass, particularly the Chlorophyta,

Pyrrhopyta, and Cyanophyta. Salinity, (chloride concentration) decreased from 400 ppm 

in the late 1960’s to 208 ppm in the 1980’s. Reduction of salinity concentrations is 

considered to be the primary driving factor in the establishment of E. drieschi 

throughout the lake. Salinity has begun to increase recently and is currently 280 ppm Cl - . 

E. drieschi shows a strong seasonal periodicity with densities highest in the 

winter / spring and very low in summer / fall. Many freshwater diaptomids, produce two 

types of eggs: a subitaneous or immediately hatching egg and a diapausing or benthic 

resting egg. The pelagic population of E. drieschi recovers annually (after overturn) 

from a “bank” of these benthic resting eggs which were laid down the previous season 

when lake temperature increased above their range of thermal tolerance (> 22 0 C). The 

benthic resting eggs of E. drieschi collected from the sediments are not morphologically 

different from subitaneous eggs when examined with a scanning electron microscope, 

however, they can be distinguished under a light microscope using Lugol’s stain 

(Lohner 1990). The SEM revealed that the eggs’ surface were smooth, with no spines or 

projections. This proposes a potential vector for resting egg transport via the gut 

contents of fish. Viable resting eggs were found in the gut of larval Clarias gariepinus 

from the lake. It is possible that E. drieschi may have been introduced into the lake by 

migrating, piscivorous birds, and distributed by benthic feeding fish. 

The biological invasion of an ecosystem by any organism may be indicative that 

the system has undergone modifications, (usually man-made) which allow the invading 

species to become established. An invading organism is defined as one that is found 

anywhere outside its previous range. A small percentage of invasions however, are 

actually successful. E. drieschi appears to have successfully invaded the Kinneret 

system by taking advantage of a period of low chloride concentration (

occupying a niche and using its adaptive ability to produce resting eggs to escape the 

high summer temperatures.

Research Objectives 

The object of this research is to present documentation of the life cycle of the 

diaptomid copepod Eudiaptomus drieschi (Poppe & Mrazek 1895) in Lake Kinneret 

during the years 1994-2000, specifically, to follow population dynamics in the field by 

measuring secondary production, seasonal distribution patterns, and life stage 

development in the laboratory. Preliminary studies were conducted in 1994-95, and 

continuous monitoring began in 1996. Ontogenetic distribution, diel changes in the 

pelagic population, and benthic resting egg distribution are also investigated. Field 

observations in conjunction with laboratory measurements will be used to examine the 

temperature and salinity tolerances of E. drieschi. The physical and biological changes 

that have occurred in Lake Kinneret which have allowed for the invasion of this species 

to the pelagic regions of the lake will be discussed. A possible vector for resting egg 

distribution will be suggested.

1. General Introduction 

1.1 Kinneret Background 

Lake Kinneret (32 0 42’ and 32 0 53’N) is located in northern Israel in the Syrian- 

African Rift Valley. It is a subtropical, monomictic lake, and the only natural freshwater 

lake in Israel (Gophen 1984, 1989). Mixing usually begins in early winter (December), 

and turnover is usually completed by mid- January, which means the lake is thermally 

stratified early summer through late fall (June-December). The lake surface area is 170 

km 2 with a mean minimum depth of 24 m and maximum of 42 m when the lake level is 

at 209 m below Mean Sea Level. The average yearly temperatures range from 14 0 C to 

30 0 C. Historically, the lake level has been seen to vary widely from -212 m to -209 m. 

Currently, due to consecutive drought years, the lake is at a previously unrecorded low 

level of –214.23. 

The lake is situated at the boundary of semi-arid and moist climatic conditions. As a 

result, there are strong seasonal patterns of wind and rainfall in the lake area. The 

amount of rainfall throughout the winter period (October-April) is highly variable and 

not uniform across the lake. The monthly average wind speeds are higher in summer 

than in winter, and winter winds are predominantly from the east, while summer winds 

are from the west. Two periods of “weak wind” generally occur in spring and autumn 

(Serruya 1978). The external winds in conjunction with the internal temperature regime 

greatly influence water movement. A thermal gradient, some 2-3 0 C difference from the 

surrounding waters, begins to develop during the spring (March–April) which generates 

a changeable barrier (thermocline) in the upper water body (8-10 m). Below this barrier, 

oxygen and pH begin to decrease and CO 2 is present on the bottom. Towards the 

summer, the increased warming causes the thermocline to deepen which effectively

divides the lake with a warm, oxygenated, CO 2 depleted epilimnion, and a cold, anoxic 

hypolimnion with H 2 S and CO 2 .The general circulation patterns are seasonal and 

determine the formation of the thermocline and movement of the internal seiche. 

The main source of water to the Kinneret is the Jordan River system. There are also 

thermal-mineral springs along the shores and on the lake bottom. These springs 

influence the chloride concentration of the lake waters. The pH values of the lake water 

are also seasonal, with the lowest values observed during the turnover and highest values 

in late spring (7.5-8.9). Oxygen levels in the epilimnion and hypolimnion are influenced 

by external weather conditions and consequently vary from year to year. 

Bottom sediments are made up of a dark, flocculent upper layer of 2-5 cm. thickness, 

and a more compact, gray material below. Sedimentation rates vary at specific locations: 

higher in the north and lowest in the central deep waters. There is also a seasonal 

difference in sediment deposition. (Serruya 1978). 

Biota 

There are over 250 species of phytoplankton in the Kinneret including the 

dinoflagellate Peridinium spp. (Gophen & Pollingher 1985). The bloom season of the 

Peridinium occurred with great regularity from late winter to early spring (February- 

May) but the highest number of species in the lake is represented by the Chlorophytes. 

The presence of such temperate species as Rhodomonas sp. and Cryptomonas sp., 

indicates that cold stenothermic forms can survive during the winter period in warm 

lakes. The fall season is dominated by nanoplanktonic species with low species 

diversity, however during the winter, species diversity is highest. Phytoplankton 

biomass peaks in the spring and the diversity begins to decline. Summer shows a drastic 

decrease in algal species diversity, with the nanoplanktonic green algae predominating

Over 30 different zooplankton species occur in Lake Kinneret. Zooplankton biomass 

is dominated by the Cladocera (58%). The most prevalent species are Bosmina 

longirostris (O. F. Muller), B. longirostris var. cornuta (Jurine), Ceriodaphnia reticulata 

(Jurine), C. rigaudi (Richard), Diaphanosoma lacustris (Korinek), and D. brachyurum 

(Lieven). The pelagic Copepoda (35%) are represented primarily by the cyclopoids 

Mesocyclops ogunnus Onabamiro, 1957 and Thermocyclops dybowskii (Lande). 

Eucyclops serrulatus (Koch, Sars), a benthic form, appears occasionally in the pelagic 

waters. There is a rich benthic harpacticoid fauna (Por 1966, 1968a, 1968b) in the 

shallow waters, representatives of which appear sporadically among the pelagic 

plankton after severe storm events. The Rotifera have the lowest biomass (7%), but the 

highest number of species. The predominant forms are Keratella cochlearis (Gosse), K. 

valga tropica (Ehrenberg), Synchaeta pectinata Ehrenberg, Asplanchna brightwelli 

Gosse, Polyarthra remata Skorikov, and Hexarthra fennica (Levander). Less frequent 

members of the rotifer plankton are Ascomorpha saltans Bartsch, Trichocerca sp., 

Filinia longiseta (Ehrenberg.) Brachionus angularis (Gosse) and Collotheca sp.. Total 

zooplankton biomass is high throughout the winter / spring (42-55 g m -2 ) and ranges 

from 25-36 g m -2 during summer/fall. Cyclopoid copepod biomass averages 18 g m -2 

and shows little seasonal variation. Cladocera and rotifer biomass is reduced throughout 

the summer months. 

The first report of the zooplankton of Lake Kinneret was the work of Richard 

(1890). This work was based on material collected by Barrois who made observations on 

the vertical distribution of the predominant cyclopoid species in the lake (Serruya 1978). 

Zooplankton collected by Annandale in 1912 was analyzed and described by Gurney 

(1913). He mentioned the presence of Daphnia lumholtzi (Sars) which had not been

found previously. The early faunistic survey of Bodenheimer (1935) from Lake 

Kinneret, listed four cyclopoid species including Cyclops varicans (Sars) which Barrois 

had considered as non-resident. Both Gurney and Bodenheimer list species that were not 

mentioned by previous surveys: Daphnia lumholtzi and Cyclops leuckarti (Claus) 1857. 

These early investigations, however, dealt primarily with samplings from the shallow 

littoral (Gitay 1968). 

Samples collected from 1948-1950 by Dr. H. Lissner, of the Sea Fisheries Research 

Station, were examined and reported on in the work published by Komarovsky (1959). 

This paper is the first to give a detailed list of 22 zooplankton species from the open 

water, as well as quantitative data on their seasonality. Yashuv and Alhunis in 1961, 

published information from a study conducted in shallow water, during May 1956 to 

July 1957, where they listed 35 zooplankton species. In 1968, the newly established 

Kinneret Limnological Laboratory began a routine, interdisciplinary monitoring 

program of the lake. Pelagic zooplankton have been surveyed continuously on a bimonthly 

basis, since 1969 to the present, under the supervision of Prof. Moshe Gophen. 

This investigator has been responsible for the inventory of the routine zooplankton 

samples from 1980 to the present. 

1. 2 Long- term Changes in Kinneret Ecosystem: 

Physical 

The building of a dam at the southern end of the lake in 1932 at Degania, brought 

under man-made control the natural rise and fall of the lake level. Operation of the dam 

caused an overall decrease of the average water level, however, the dam ceased active 

operation in 1948 and is only used to regulate floodwaters of the Southern Jordan River.

The National Water Carrier, which was constructed in 1964, is used to pump water from 

the lake in order to distribute it to other areas of the country, and as a result, also 

influences the lake water level. In 1965, a saline spring diversion canal was constructed 

to aid in reducing the high concentrations of sodium chloride in the lake. Before the 

construction of the canal, salinity varied from 380-400 ppm Cl - . Since the canal began 

operation and in conjunction with heavy flood years, salinity has declined by nearly 

30%. The annual average for 1988 was 208 ppm Cl - and in the early ‘90’s, it was 218 

ppm Cl - . Recently, due to the low lake level caused by severe drought conditions, 

diversion of spring waters to the canal has ceased and chloride concentration for the lake 

is currently (2001) 380 ppm Cl - . 

Biological 

Changes in the plankton population dynamics reflect some of the physical changes 

that have recently occurred in the lake. Phytoplankton diversity (non-Pyrrophyta) was 

seen to have increased (Berman et al. 1992). Although total zooplankton biomass 

declined for a number of years (Gophen et al. 1990), zooplankton species diversity of 

the pelagic waters has increased. The cladocerans Moina rectirostris (Leydig) 1860 and 

Chydorus sphaericus (O. F. Müller) 1785 which had previously been considered 

incidental members of the benthic fauna (Gophen 1978), are currently routinely found in 

pelagic samples. Among the rotifers, Collotheca sp., Anueriopsis fissa (Gosse) and the 

colonial Conochiloides coenobasis Hlava, are also regularly found in pelagic samples 

(Gophen 1992). The copepod Eudiaptomus drieschi (Poppe & Mrazek 1895) is the first 

diaptomid copepod to be reported among the “new” members of the open water fauna.

1.3 Previous Diaptomid Data from Israel and the Kinneret 

Komarovsky’s paper (1959), the first to give a detailed list of 22 zooplankton species 

including those from the open water, notes especially, “the complete absence of 

Diaptomids among the Copepoda” in the lake, (although they were found in rainpools in 

the area). The Yashuv & Alhunis paper (1961) listed the diaptomid Eudiaptomus 

gracilis (Sars) among the plankton from a shallow water station in the southwest region 

of the lake. Por (1968, 1984) recognized E. gracilis as an accidental “visitor”, not 

belonging to the Kinneret fauna. Gophen (1972) also recorded the presence (rare) of E. 

gracilis in the lake and found them represented in the gut contents of gray mullet 

fingerlings collected from the littoral (Gophen 1979, Shapiro 1998). Dimentman & Por 

(1985) collected Arctodiaptomus similis similis (Baird 1859) from the lake during the 

winter months, but it was considered to be the incidental result of winter floods. Adult 

Arctodiaptomus similis similis are occasionally found in inshore waters, in close 

proximity to commercial fish pond establishments. Juvenile stages of A. similis similis 

have never been found in routine samples (pers. obs., author). In 1987, Por (in litteris) 

identified the diaptomid copepod that was appearing with increasing frequency in 

routine, bimonthly zooplankton samples from pelagic stations in Lake Kinneret as 

Eudiaptomus drieschi (Poppe & Mrazek 1895). Prof. Dr. Ertunc Gunduz of Hacettepe 

University, Turkey, concurred with this identification (pers. comm). It is suspected 

(although not validated), that the sporadic reports of E. gracilis in the Kinneret may, in 

fact, have referred to E. drieschi. Specimens of E. drieschi from the Kinneret are 

deposited in the Aquatic Invertebrate Collection at the Hebrew University of Jerusalem. 

In Israel, the Diaptomidae are represented by four taxa: Lovenula (Neolovenula) 

alluaudi (de Guerne & Richard 1890); Arctodiaptomus (Arctodiaptomus) similis similis

(Baird 1859); Arctodiaptomus (Arctodiaptomus) similis irregularis.; and Hemidiaptomus 

(Hemidiaptomus) gurneyi canaanita, Dimentman & Por 1985. Lovenula, distributed 

throughout Africa and around the Mediterranean, typically inhabits semi-permanent 

water bodies and spring basins with chloride concentrations of 788 mg l -1 . A. similis 

similis is the most common diaptomid in Israel. It is found in temporary rainpools 

where salinity is typically low. Hemidiaptomus also inhabits rainpools in the northern 

and Coastal Plain areas. 

In 1895, Poppe and Mrazek found Diaptomus drieschi among the material collected 

by H. Driesch for the Hamburg Zoological Museum in Sri Lanka (Ceylon). Almost no 

work had been done on this species until its revision by Kiefer, in 1932. Kiefer placed 

D. drieschi in the new genus Eudiaptomus because of substantial differences in the male 

and female 5th legs. E. drieschi has been recorded later from southern Yugoslavia 

(Lake Skadar, Montenegro), northern Greece (Corfu), and Turkey (Lakes Beysihir, 

Egridir, and Kovada), (Kiefer 1968, Gunduz 1998). These water bodies are all 

characterized by low salinity, and moderate temperatures.

Fig 1 

Map of Lake Kinneret -Israel 

Kinneret Limnological 

Laboratory 

F 

-220 

-230 

32 

o 

50 

/ 

-240 

-250 

N 

o 

32 45 

/ 

35 o / 

32 

5 Km 

35 o 35 

/ 

35 

o 

38 

/ 

Figure 2: Map of Lake Kinneret (Seruuya, 1978) showing sampling station F.

2. Methods and Materials 

2.1 Seasonal Abundance Studies (Routine Field Sampling) 

Samples were collected weekly from Station F (fig 1) using a 20 L plexiglass 

Schindler - Patalas trap. Duplicate water samples from 1, 5, 10, and 20 meters were 

concentrated through a 20 m mesh sieve net and preserved separately, in 4% sugar 

(Haney & Hall 1972) formalin (32g sugar / liter formalin). 

The entire sample was counted at 20x on a Wildco plankton wheel (10 ml vol.) 

with a Wild binocular dissecting microscope All life stages were identified (NI - VI, CI - 

V, adult males and females) and counted separately. Egg bearing females were noted 

separately from adult females without eggs, and the numbers of eggs per female were 

counted. Samples from fixed depths were counted separately to examine vertical 

distribution, then the counts were pooled for population dynamics. 

Diapausing (resting) eggs were distinguished from subitaneous (immediately 

hatching) eggs (for one season) in preserved samples by adding Lugol’s solution to the 

samples and examining them under an inverted microscope (Lohner 1990). 

Sex ratios were compiled using a chi – square test for goodness of fit: 

X 2 = (f – f^) 2 (1) 

f^ 

f is the observed frequency, and f^ the expected (Sokal & Rohlf 1973). 

2.2 Benthic Resting Eggs 

Lake bottom sediments were collected monthly using a standard gravity corer 

with plexiglas cores (inner diameter: 5.2 mm, length: 47.0 cm.) from the RV Hermona 

at sampling station F (maximum depth 22 meters). Cores were also taken from random 

sites around the lake. The cores were removed to the lab and sediments were processed 

within one hour of collection, or held upright in cold (4 0 C) storage until sliced. The 

entire core (38.5 cm.) was sectioned into 1 cm. slices. (Investigations showed that viable 

resting eggs were rarely found at depths below 12 cm. in the sediments. For that reason, 

subsequent cores were sectioned only to 15 cm. depth.) Sediments were weighed and 

divided; half for dry weight determination and half for egg counts. Sediment samples for 

establishing dry weight were put into pre-weighed foil containers and placed in a drying 

oven (100 o C) for 48 hours. The sediment portions containing the eggs were processed

using a modification of the sugar flotation method introduced by Onbe (1978) and 

described in Ban & Minoda (1992). Sediments were washed with filtered lake water 

(0.45 µm) through a 45.0 µm mesh sieve. Material remaining on the sieve was rinsed 

into 250 ml. Nalgene centrifuge bottles, combined with a supersaturated sugar solution 

(1 kg per 1 liter), and centrifuged at 3,000 rpm for 5 minutes. The supernatant was then 

washed through a 20 µm mesh net to remove the sugar and collect the eggs. Eggs were 

carefully rinsed into petri-dishes and counted under a Wild binocular dissecting 

microscope. Diaptomid eggs were incubated in controlled light and temperature 

conditions (Shel-Lab Low Temperature Incubators) in filtered (0.45µm) lake water and 

hatching of new - born nauplii was recorded. 

The number of benthic resting eggs per gram of dry weight sediment was obtained by: 

(a / b) * (# eggs / DW (g) ) = # eggs / g (DW) (2) 

where a is the wet weight (g) of the sediment portion to be dried, b is the wet weight (g) 

of the sediment portion for egg counts. The number of eggs per portion is then divided 

by the dry weight (DW) of sediments. Then the density (number of eggs per square 

meter) was calculated for each sample by finding the number of eggs in the surface area 

of the core ( S.A. = square of r * ), which is divided into the number of eggs multiplied 

by 10 3 . 

.2. 3 Diel Survey 

Diel sampling took place at Station F on April 1-2 (spring), September 29-30 

(fall) 1997, and June 9-10 (summer) 1998. The research vessel (RV Hermona) was on 

station throughout the survey periods. Duplicate zooplankton samples were taken every 

2 hours with a 20 L Schindler - Patalas trap over a 24 hour period (dawn / dusk / dawn). 

Zooplankton samples were taken from depths 1, 3, 5, 7, 10, 15, and 1meter from bottom. 

Samples were filtered through a 20µm mesh net and preserved in 4% buffered formalin. 

Samples were concentrated through a 20µm mesh net to a smaller volume in the lab. 

The entire sample was counted and all life stages were enumerated with a Wild 

binocular, dissecting microscope. The parameters: chlorophyll, oxygen, temperature, 

light, and Secchi disc depth were measured. 

Phytoplankton chlorophyll a samples were taken with a 5-liter Van Dorn bottle 

at each sampling depth. The water was filtered on-board for size fractionation of net

(>20 µm) and nano (20 

m) and nano (

2.4. Experimental Studies 

2.4.1. Development 

E. drieschi was collected from the lake (in the vicinity of Station F) 

by 5 minute, horizontal plankton net (500 m mesh) tows from the RV Hermona . 

Mature adults were individually selected using a modified Pasteur pipette attached to 

flexible tubing and controlled by mouth. Animals were maintained in 1liter vessels with 

filtered lake water (0.45 m) under controlled laboratory conditions. Prior to each 

experiment, animals were incubated for at least one generation at treatment conditions 

(temperature and light) and given food ad libitum. Food was a mixture 

of the algae Chlamydomonas sp. and Rhodomonas sp. (0.6ml in a 1 : 1 ratio) obtained 

from stock cultures maintained at the Kinneret Limnological Laboratory. 

Length measurements 

Body length measurements of E. drieschi were obtained by using a computer 

assisted video camera system, CAPAS (Computer Assisted Plankton Assessment 

System, (Hambright 1996) with an inverted microscope. The system was calibrated with 

a Wild stage micrometer for 500 m (+ 0.15). Copepods were pipetted into 5 ml. 

phytoplankton settling chambers (Hydro-Bios, Kiel), and copepod lengths were 

measured from the top of the head to the end of the anal somite (excluding the caudal 

ramus). The setae were excluded in the naplii length measurements. Although the sex 

can be distinguished at developmental stage CIV, males and females were only counted 

as such after they had completed the CV molt. At least 50 individuals of each life stage 

were measured.

Stock preparations 

Females with ripe ovaries for the growth and development studies were isolated 

and pipetted into 100 ml. Erlenmeyer flasks containing 50 mls. filtered (0.45 m) lake 

water. The total alga cell concentration of the feeding suspension was kept in excess of 

5 x 10 4 cells ml -1 . Algal cell concentration was maintained by determining the 

concentration of the stock culture by direct cell counts with a hemocytometer ( 0.100mm 

x 0.0025 mm 2 ) and adding the appropriate volume to maintain experimental 

concentrations. The average concentration of Chlorophyta in the lake throughout the 

period that E. drieschi is present, ranges from 1.31 x 10 4 – 9.76 x 10 3 cells ml -1 . 

Therefore it is assumed that experimental conditions provided sufficient nutrition, and 

food was not a limiting factor in these experiments 

Culture vessels were maintained in temperature controlled (+ 0.1) incubators 

(Shel – Lab) in a constant dim light regime. The water and food suspension was changed 

twice a week. Observations were made at least twice daily for the duration of the 

experiments. 

Mature males, for the development studies, were paired with gravid females, and 

pairs were observed regularly until the females produced a clutch of eggs. Time elapsed 

from successful mating to hatching of the eggs was recorded for all pairs. Ten newly 

hatched (pre-molt) nauplii from each clutch were removed to new flasks and 

development followed and documented to adulthood. Egg development, duration of each 

naupliar stage, and time spent in each copepodite stage was examined at a range of 

temperatures: 12 0 , 18 0 , 20 0 , 22 0 , and 24 0 C. This range include those temperatures E. 

drieschi would normally experience in the lake throughout January - June. Animals

incubated at 24 0 C exhibited extremely high mortality, and did not reach the third 

naupliar stage. These results were not included in the analysis. 

2.4.2 Data Analysis 

Secondary production (P) of the lake population was calculated based on experimental 

measurements utilizing the growth increment method from Downing and Rigler (1984): 

P = N (m max - m min ) / D (3) 

In this calculation, N, is the average number of individuals in a size class at a specific 

time. Maximum and minimum biomass (m min and m max ) was measured from the 

experiments. Development time (D), was taken as the time it took an individual to grow 

from m min to m max . 

Finite birth rate (B) was obtained by measuring embryonic development (D) over a 

series of temperatures in the laboratory, which was then related to the number of eggs 

from the field data (recruitment of eggs to nauplii): 

Eggs / L / day = Eggs / Liter / day (4) 

D 

This is then divided by the size of the population at the specific time to give the birth 

rate relative to the field population sampled at the time: 

B = Eggs / L / day 

No./L 

(4a) 

The instantaneous birth rate (b), was calculated as: 

b = ln (1+B) (5)

when the population meets conditions where b and d are both constant from t 1 to t 2 as 

estimated by the rate of change of the population: 

r =, lnN t – lnN 0 (6) 

t 

where N 0 is the initial population and N t is the number of individuals at a specific time 

sampled and t is the time interval. 

Instantaneous death rate (d) is then calculated: 

d = b – r (7) 

Specific length growth rates (C L )were calculated using: 

C L = ln (L 2 –L 1 ) 

t 2 – t 1 (8) 

In which L and t are measured initial and final lengths (geometric mean) and 

development times found in Tables 1 and 2, respectively. 

Biomass was calculated by using the number of individuals (N) and their average 

weight (M, mg ww ): B = N * M. 

Production to biomass ratios (P/B) were calculated for the field population. 

Length was measured and weight (biovolume) calculated: 

Prolapsed sphere = 4 / 3 (a / 2) * (b / 2) 2 (9) 

Where a is measured length in mm and b is width (Bird & T-Praire 1985, Culver et al 

1985, Lawrence et al 1987).

2.4.5 Salinity tolerance 

Salinity tolerances were measured using varying concentrations of an artificial saline 

solution for Kinneret water, “Salina” (A. Nishri, pers comm): 

NaCl 

KCl 

MgCl 2 6H 2 0 

CaCl 2 

Na 2 S0 4 

8700 mg / l FLW 

350 mg / l FLW 

7000 mg / l FLW 

147 mg / l FLW 

77 mg /l FLW 

Table 4: Artificial saline solution (“Salina”) used in salinity tolerance experiments. 

The following concentrations were used in the experiments: High - 400 mg Cl - / l, 

Medium - 280 mg Cl - / l, Lake - 225 mg Cl - /l, and Low - 100 mg Cl - / l. Experimental 

concentrations were obtained using “Salina” with filtered Lake Kinneret water (FLW 

0.2µm). The low concentrations were obtained by diluting filtered lake water (FLW) 

with filtered water from the upper Jordan River (20 mg Cl - / l). 

Adult animals (5 females, 2 males) were each placed in 32, 50 ml Erlenmeyer flasks 

with 25 ml experimental solution. Half of the flasks were placed in a temperature / light 

controlled incubator at 18 0 C, with dim light conditions and the remaining half were at 

12 0 C. Flasks were examined regularly until over 50% mortality was reached.

2.4.4. Food Requirements 

Mature adult females (30) were placed in individual cell chambers (Corning cell 

wells, 3 mls.), and given high (10 5 cells / ml) and low (7 x 10 3 cells / ml) concentrations 

of algal food (Chlamydomonas sp.). Concentration of algal cells were determined by 

direct count of observed changes in number of cells in suspension, with a 

hemocytometer. Percentage survival of individuals at the different levels of food 

concentrations were compared.

3. Results 

3.1 Descriptive taxonomy (General) 

The diaptomid copepods are members of the most common group of freshwater, filter 

feeding calanoids, the Diaptomidae. There are over 400 species in about 50 genera. 

They play an important role in freshwater ecosystems as food for fish and invertebrate 

predators. As is typical in crustacean morphology, the diaptomid metasome (prosome) 

or cephalothorax is divided into a head and thorax, and the urosome is made up of the 

abdominal and genital segments. The urosome terminates with a pair of structures called 

caudal rami, which end in caudal setae (Williamson 1991). The metasome may have 

between 4 to 6 segments depending on the species. The head bears the first antenna or 

antennules, second antenna, mandibles, maxillules, and maxillae. The thorax has the 

maxillipeds, four pairs of swimming legs and a pair of modified 5 th legs. Diaptomids are 

sexually dimorphic. The female 5 th legs are symmetrical and well developed (Fig. 2a), 

while the male 5 th legs are highly asymmetrical and modified for reproduction (Fig. 2b). 

The setation and armature of the male right anntenule is also of key significance in 

species identification (Fig 2c-d). The first antennae posses both chemoreceptors and 

mechanoreceptors that function in feeding, locomotion, and reproduction. They are not 

flexible and are raised or relaxed by increased or decreased blood pressure. 

The shape and armature of the female genital and last thoracic segment are 

important morphological features for distinguishing between species (Fig 2e). The 

female genital segment is composed of 3 fused segments. The antennules of the male 

diaptomids are asymmetrical, the right antennula is geniculate for grasping the female 

during copulation (Fig 3b). It is made up of 21-22 segments that can be divided into 

three sections.

c) 

b) 

a) 

d) 

e) 

• Figure 2: a) female 5th leg (P5), b) male 5th leg, c) Detail of penultimate segment of male right antenna, 

• d) detail of setation of male right antenna, e) Female genital segment showing armature. (Drawings courtesy 

of F.D. Por).

a.) 

b.) 

c.) 

d.) 

• Figure 2a-d.: a)Male fifth leg (P5).,b).Adult male., 

• c). Adult female with egg clutch., d). Adult female with 

attached spermatophore.

23 

The female antennules are symmetrical. They are thin and usually as long or longer than 

the length of the body. They consist of 25 segments (Fig. 3c). 

Diaptomids pass through six naupliar (NI-VI) and six copepodid (CI-V) stages by 

molting, the final molt produces the adult which does not molt further. Adult females are 

fertilized by a spermatophore, which is attached by the male to the female genital 

segment (Fig 3d). Females require a new mating for each clutch produced. Eggs are 

carried in a single sac under the genital segment. 

Developmental Stages 

Average body length (in mm) of naupliar stages (excluding setae) and average body 

length of copepodite stages of Eudiaptomus drieschi from Lake Kinneret (excluding 

setae) are given in Table 1. Average of 50 individuals from each stage. 

Table 1: Average body length (in mm.) of naupliar and copepodite stages of Eudiaptomus drieschi 

(average of 50 individuals of each stage) with standard deviations. 

(in mm) NI NII NIII NIV NV NVI CI CII CIII CIV CV 

Average 0.141 0.180 0.213 0.252 0.358 0.393 0.499 0.655 0.798 1.107 1.165 

St.Dev. 0.002 0.010 0.013 0.01 0.019 0.013 0.019 0.014 0.030 0.105 0.097 

The NI stage is characterized by 3 pairs of incompletely developed appendages (first 

antennae, second antennae, mandibles) and no caudal setae. The first maxillae appears in 

NII. In the later or metanaupliar stages, maxillule develop (NIII, NIV). In the fifth stage 

(NV), the maxilla become visible. The maxilliped and rudimentary legs are present in 

the sixth and final naupliar stage. The second pair of legs appears in NVI as 

unsegmented buds. 

The copepodite stages are recognized by the number and segmentation of legs: 2-5. 

In C I, legs 1 and 2 are recognizably developed, but the endopod and exopod are 

unsegmented. Leg 3 appears as a “bud”, and after the CII molt, the “bud” becomes a

segmented leg and the next leg bud appears. It is possible to distinguish between the 

sexes by stage C IV as all five legs are present, but not fully developed. Development is 

completed by stage C V. 

Eudiaptomus drieschi densities in Lake Kinneret, 

Station A 

Number of organisms L -1 

20 

10 

0 

1970 

3.2 Seasonal Distribution 

Figure 6: Multi annual population density of E. drieschi in 

the Kinneret 

Densities (number per liter) of E. drieschi from the KLL database (Fig. 6) show the 

appearance in the lake of this organism from 1986. 

Overall copepod biomass (g m -2 ) over the study period is shown in Fig. 7a. The 

Copepoda make up approximately 35% of total zooplankton biomass. E. drieschi 

contributes less than 3% to the total zooplankton biomass (Fig. 7b).

25 

Monthly Copepod Biomass 

25.0 

20.0 

15.0 

10.0 

5.0 

0.0 

Jan-96 

Apr 

Jul 

Oct 

Jan-97 

Apr 

Jul 

Oct 

Jan-98 

Apr 

Jul 

Oct 

Jan-99 

Apr 

Jul 

Oct 

Jan-00 

Apr 

g -1 m 2 

Jul 

Oct 

a.) 

Contribution of E. drieschi biomass to Total Zooplankton 

Biomass 

2.4% 

2.0% 

1.6% 

1.2% 

0.8% 

0.4% 

0.0% 

b.) 

Figure 7: a) Total monthly copepod biomass (g/m 2 ) in L. Kinneret. 

b) Percent E. drieschi biomass to total zooplankton biomass. 

E. drieschi does not produce identifiable cohorts, but reproduces continuously 

throughout the months it is found in the water column (Dec-Jul) as indicated by the rate 

of change (Fig. 8a). Instantaneous birth rate (b) is quite similar to instantaneous death 

rate (d) shown in Figs, 8b, c. The calculated instantaneous rate of change is small, thus 

giving the population the appearance of being in “steady-state”. 

Daily secondary production (biomass accumulated per unit time) to biomass was 

calculated for the years 1996-98. The P/B ratios for cyclopoid copepods in the Kinneret 

range from: 0.10-0.16. The P/B ratios of E. drieschi from 1996-97 show a slightly higher 

secondary production rate with a decline beginning in 1998 (Fig. 9a-d). Ratios of 0.1- 

0.22 have been found for species of Diaptomus in eutrophic lakes (Ponyi et al 1982).

26 

Rate of Change 

0.300 

0.200 

0.100 

0.000 

-0.100 

-0.200 

-0.300 

a). 

b). 

Instantaneous Birth rate 

4.0 

3.0 

2.0 

1.0 

0.0 

Jan-96 

Apr-96 

Jul-96 

Oct-96 

Jan-97 

Apr-97 

Jul-97 

Oct-97 

Jan-98 

Apr-98 

Jul-98 

Oct-98 

Jan-96 

Apr-96 

Jul-96 

Oct-96 

Jan-97 

Apr-97 

Jul-97 

r = ln(N t - lnN 0 ) / t 

Oct-97 

Jan-98 

Apr-98 

Jul-98 

Oct-98 

Instantaneous Death Rate 

3.0 

d = b - r 

1.5 

0.0 

Jan-96 

Mar-96 

May-96 

Jul-96 

Sep-96 

Nov-96 

Jan-97 

Mar-97 

May-97 

Jul-97 

Sep-97 

Nov-97 

Jan-98 

Mar-98 

May-98 

Jul-98 

Sep-98 

Nov-98 

b = ln (1 + B) 

c). 

Figure 8: a) Rate of change (r), b) Instantaneous death rate (d), c) Instantaneous 

birth rate (b) for E. drieschi population in Lake Kinneret.

E. drieschi has a strong seasonal periodicity (Figs. 10a-c). The population begins to 

appear in mid-winter (late December/January), and continues to increase throughout 

winter into spring. The population reaches peak abundance in April-May, 

after which numbers decline through June. By the end of June/July, numbers have 

declined to the point of being undetectable with routine sampling methods (< 0.03/ m 3 ).

Total E. drieschi biomass ( mg / m 3 ) 

120 

100 

80 

60 

40 

20 

0 

1994 

Daily 

P / B = 0.33 

50 

45 

40 

35 

30 

25 

20 

15 

10 

5 

0 

Net biomass Production (mg / m 3 / 

d) 

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 


600 

500 

400 

300 

200 

100 

0 

1996 

Daily 

P / B = 0.22 

140 

120 

100 

80 

60 

40 

20 

0 

Net biomass Production (mg / m 3 / 

d) 


450 

80 


400 

350 

300 

250 

200 

150 

100 

50 

1997 

Daily 

P / B = 0.20 

70 

60 

50 

40 

30 

20 

10 

Net biomass Production (mg / m 3 / d) 


0 

180 

160 

140 

120 

100 

80 

60 

40 

20 

0 


1998 

Daily 

P / B = 0.12 


40 

35 

30 

25 

20 

15 

10 

5 

0 

0 

Net biomass Production (mg / m 3 / d) 

Figure 9: Seasonal Productivity / Biomass ratios (P/B) for E. drieschi in 

L. Kinneret for the years 1994, 1996-1998.

Total Number of Organisms, L -1 

80 

70 

60 

50 

40 

30 

20 

10 

0 

1996 

30 

26 

22 

18 

14 

10 

Average Water Temperature ( 0 C) 

a.) 

Jan 

Feb 

Apr 

May 


Jul 

Sep 

Nov 

40 

35 

30 

25 

20 

15 

10 

5 

1997 

30 

26 

22 

18 

14 


b.) 

0 

Jan 

Jan 

Feb 

Feb 

Mar 

Mar 

Apr 

Apr 

M… 

M… 

Jun 

Jul 

Jul 

Jul 

Aug 

Sep 

Sep 

Oct 

Oct 

Nov 

Dec 

10 

1998 

c.) 


12 

10 

8 

6 

4 

2 

0 

Jan 

Feb 

Mar 

May 

Jul 

Sep 

Oct 


30 

26 

22 

18 

14 

10 

Figure 10: a. – c.) Seasonal periodicity of E. drieschi at Station F, 

1996 – 98.

Reproduction is continuous throughout the period that E. drieschi occurs in the 

water column, as seen by the presence of nauplii, copepodites, and both sexes in all 

samples. Number of eggs per clutch varies greatly (8-26). The highest number of eggs 

per female occurs in Jan./Feb. (16-22). (One female, sampled in February, was found 

carrying a clutch of 66 eggs.) The number of females carrying eggs increases in spring 

with an average clutch size of 12-18. Total annual biomass averaged between 1-1.4 

mg/ l (wet weight). The greatest biomass occurred in the spring with values reaching 

2.01 mg/l (wet weight). Figure 11 shows the percentage of egg bearing females present 

in the water column plotted with average water temperature (r 2 = 0.56, P5) in relation to Lake 

Temperature, 1997 - 98 

Females with eggs (%) 

100% 

80% 

60% 

40% 

20% 

0% 


28 

26 

24 

22 

20 

18 

16 

14 

Lake Temperature 

12 

10 

Figure 11: Seasonality of egg-carrying adult female E. drieschi (percent of total 

females) versus lake temperature (1997-1998) 

There was a tendency for individuals to occur at greater depths as the seasons 

progressed. By early to mid summer, very low numbers of organisms were found in the 

upper water column (

decline of E. drieschi in the water column, and increasing salinity (Fig. 12a), and 

increasing temperature (r 2 = 0.75, P

3.3 Sex Ratio 

The ratio of adult females to males is given in Table 2 .The years 1995-97 showed a 

slightly male biased sex ratio (P

Average Depth of Individual = x 1 z 1 + x 2 z 2 + ….+ x n z n (10) 

x 1 + x 2 + …x n 

where z 1 is depth 1 and z 2 is depth 2, x 1 is the number of individuals at depth 1, x 2 is the 

number of individuals at depth 2 and so on to depth n (Wetzel 1991). Table 3 gives the 

average depth distributions for the spring 24 hour survey: 

Table 3: Average depth distribution of E. drieschi life stages, Station F, Spring survey, April 1997 

---------------------------------------------------------------------------------------------------------- 

Day 

Mean Depth Distribution (m) 

----------------------------------------------------------------------------------------------- 

Adults 13.48 

Juveniles 8.26 

Nauplii 9.62 

-------------------------------------------------------------------------------------------------------- 

Night 

Mean Depth Distribution (m) 

-------------------------------------------------------------------------------------------------- 

Adults 7.50 

Juveniles 5.72 

Nauplii 8.76 

---------------------------------------------------------------------------------------------------------- 

Spring temperature profiles showed an average temperature difference of 3 0 C from 

surface to bottom. The lake is mixed with no distinct thermocline. Chlorophyll 

concentrations (g/l Chl) show maximums during full daylight in the upper depths. 

Nanoplankton (20 m) plankton in the 

water column. Oxygen profiles are typical for the season. Average Secchi depth was 

2.42 meters, and visible light diminished below 5 meters depth.

An ANOVA analysis of spring abiotic parameters versus organism density showed a 

significant effect (P

Resting Egg Distribution in the 

Sediments 1997 - 98 

Percent of total number eggs 

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 

1 

2 

3 

Sediment Depth (cm) 

4 

5 

6 

7 

8 

9 

10 

11 

12 

Figure 13: Vertical distribution of resting eggs in the sediments at Station F for 

1997 (cross fill), 1998 (solid fill). 

E. drieschi produces two distinct types of eggs: subitaneous (immediately hatching ), 

and diapausing (benthic resting) egg (Figs. 14a, b). The presence of an “extravitelline 

space” in the subitaneous eggs of preserved E. drieschi can be detected, in most cases, 

without the use of the Lugol’s solution stain (Lohner et al. 1990). The type of eggs 

carried by live females can be distinguished when viewed against a light background 

(Fig 14b). There are no outstanding morphological features of the eggs when viewed 

with a scanning electron microscope (Figs 14c, 15 a-b).

Over 80% of the resting eggs in the upper sediment layers were viable and hatched out 

after incubation, but those from the lower layers were less abundant and in poorer 

condition. Resting eggs that did not hatch within 14 days of incubation were considered 

infertile. Eggs that were damaged or deteriorated did not hatch. 

Female E. drieschi produce eggs continuously throughout the entire period they are 

found in the water column of the Kinneret. Large clutches (>22 eggs clutch –1 ) of 

subitaneous eggs are produced in the early part of the season (Jan-Mar) as the water 

begins to warm (15.9-17.0 0 C). By mid-April–May, resting eggs make up about 33.5% 

of total eggs produced and clutch sizes range from 8-22. Production of diapausing eggs 

increases to about 50% of total eggs from May to June when the water temperature 

ranges from 18-23 0 C. Subitaneous and diapausing eggs were never observed together in 

the same clutch. The size of the eggs within each clutch is varied. The average size of 

subitaneous eggs is 0.142 (+ 0.04) mm (n=300), and diapause eggs 0.153 (+ 0.04) mm 

(n= 250). 

37 

a)

) 

c) 

Figure 14: (a) resting egg from sediments (0.153 mm), (b) subitaneous egg from 

live egg-bearing female (0.140 mm), (c) detail resting egg from sediment 

(SEM x 2000)

a). 

b). 

Figure 15: a). Resting egg extracted from bottom sediments (distortion from 

drying process). b). Subitaneous egg from clutch of adult female (distortion from 

drying process).

3.6 Development 

Development Time 

Development time (number of days required) of Eudiaptomus drieschi life stages at 

the different experimental temperatures are shown in Table 4. It can be seen that 

development times are longer in animals that were reared at low temperatures, than 

those reared at higher temperatures This is compatible with previous work by Geiling 

and Campbell 1972, Landry 1975, Kamps 1978, Ban 1994, and Klein Breteler et al. 

1994. E. drieschi reared at high temperatures (>24 0 C), did not produce eggs, became 

covered in fungus and died. 

Table 4: Mean stage development time in days (average percent) with standard deviations of 

Eudiaptomus drieschi at experimental temperatures, (N=19,20) 

Temperature 12 0 C 15 0 C 18 0 C 22 0 C 

egg 10.60 (3.89) 4.58 (1.24) 1.11 (0.24) 0.85 (0.09) 

NI 2.65 (0.46) 1.71 (0.55) 0.88 (0.10) 0.93 (0.10) 

NII 3.18 (0.66) 1.74 (0.54) 1.23 (0.34) 1.00 (0.19) 

NIII 3.18 (0.59) 1.78 (0.44) 1.29 (0.30) 1.24 (0.26) 

NIV 3.25 (0.73) 1.72 (0.48) 1.33 (0.41) 1.33 (0.32) 

NV 3.13 (0.86) 1.79 (0.48) 1.60 (0.50) 1.32 (0.29) 

NVI 3.23 (0.61) 1.84 (0.24) 1.56 (0.37) 1.48 (0.40) 

CI 2.50 (0.85) 1.65 (0.40) 1.05 (0.33) 0.92 (0.17) 

CII 2.95 (0.68) 2.04 (0.70) 1.42 (0.30) 0.95 (0.21) 

CIII 2.95 (0.69) 2.05 (0.55) 1.45 (0.30) 1.06 (0.24) 

CIV 3.03 (0.51) 2.15 (0.73) 1.51 (0.41) 1.10 (0.28) 

CV 3.11 (0.93) 2.36 (0.74) 1.68 (0.43) 1.15 (0.25) 

There were clear differences in duration of embryonic development at low temperatures. 

Duration was longest (10.6 + 3.89 days) at 12 0 C. 

Development times ranged from 4.58 + 1.2, 1.11 + 0.24 and 0.85 +0.09 days for 15, 

18 and 22 0 C respectively. As temperature increased, eggs developed more rapidly; day 

at 22 0 C. Early naupliar (NI-NIII), and copepodite stages (CI-III) have shorter (p

duration of naupliar stages from copepodite stages, but a general trend in postembryonic 

development across the different temperatures was seen for all treatments. In 

many species, nauplii develop somewhat faster than copepodites, however it has been 

shown that at optimal temperature and food conditions, stage duration can be very 

similar (Fig. 15). The data show a very gradual increase in development time from NII 

through NV with a slight drop at NVI. Development time in copepodites is seen to 

increase, generally, from CI to CV. 

13% 

Stage Duration (%) 

11% 

9% 

7% 

5% 

NI NII NIII NIV NV NVI CI CII CIII CIV CV 

Stage 

Figure 15: Relative stage duration of E. drieschi. 

In Lake Kinneret, average yearly temperature ranges from 14 to 28.5 0 C. At optimal 

temperatures, (18-20 0 C) females can produce eggs within 24 hours of mating. 

Subsequent clutches are produced within 1-1.5 days (+ 0.45) at 18 0 C. Under low 

temperature conditions, females can take up to 2.5 days to produce eggs. At 

temperatures >23 0 C, females were not seen to produce eggs. E. drieschi is more 

commonly found in waters with temperatures that range from 7-22 0 C (Kiefer, 1968, 

Beeton 1981, Gunduz 1998). During the summer months when, water temperatures in 

the Kinneret can reach 30 0 C in the epilimnion E. drieschi is absent from the upper 

water column and if at all present, found only in the metalimnion (>10 m depth) where 

the temperature is less than 20 0 C.

Development Rate 

Post-embryonic development rates (amount of development per day) at the different 

experimental temperatures are shown in Figures 16 and 17. It can be seen that naupliar 

development rate proceeds fairly linearly at lower temperatures (

Specific length growth rate 

Specific growth rates in relation to temperature can be seen in Fig. 18. 

1.5 

y = 0.1063x - 0.7525 

R² = 0.9971 

C L (T)/C L (St) 

1 

0.5 

0 

5 10 15 20 25 

Temperature 

Figure 18: Specific length growth rate (C L ) of each life stage at a given temperature 

(T), in relation to intrinsic length growth rate (C L (St)). 

Specific length growth rates (C L ) of life history stages at any two temperatures were 

highly correlated (r 2 >0.9, p

3.7 Salinity tolerance 

Survival of Eudiaptomus at the different experimental salinities and temperatures is 

shown in Table 5. 

Table 5: Results of ANOVA analysis of effects of different salinity concentrations on the survival of 

E. drieschi. 

--------------------------------------------------------------------------------------------------------- 

Salinity Effect Temperature P value 

-------------------------------------------------------------------------------------------------------- 

Males 

18 o C 

High vs. Low

higher tolerance for colder temperatures at medium and low salinities. It was found that 

at low temperatures (0.001) greater percent of adult females survived at the higher food 

concentration. Since nanaplankton concentrations in the Kinneret can reach as low as 9.8 

x 10 3 cells ml –1 , wild populations of E drieschi may be able to utilize alternative food 

sources that would enable them to survive at very low food concentrations. However, at 

low concentrations of a uni-algal diet, percent survival is reduced.

4. Discussion 

4.1 Taxonomical Position 

Upon examining the original material of H. Driesch from the Hamburg Museum 

collection (1935), Kiefer declared that E. drieschi was closely affiliated to E. vulgaris. In his 

revision of the genus, Kiefer (1968) described 6 forms of E. drieschi from different 

geographic locations; Yugoslavia (Montenegro), Corfu, Turkey, and Ceylon (Sri Lanka). He 

wrote that the distribution of E. drieschi included the Mediterranean region of the Palearctic 

and, 6 0 North of the equator in the tropics. He considered this to be a very unusual 

geographic distribution of Diaptomids. Kiefer suspected that the specimen from Ceylon (Sri 

Lanka), was not actually E. drieschi, but indeed, a different species. The specimen from 

Ceylon was taken from fish ponds, where temperatures are considerably high (29-36 0 C, 

www. EDRC/ Statistics). The present research study showed categorically, that E. drieschi 

does not tolerate high (tropical) temperatures and would then confine E. drieschi’s 

distribution to Anatolia and the Levant (Dumont 1994). Based on drawings of the material, 

there are similarities in the structures of the male right antenna and the P 5 leg as well as the 

positioning of spines on the female last thoracic and genital segments, between the Kinneret 

form and those specimens which are found in Corfu. Based on these morphological 

similarities, it is highly reasonable to infer that this species may have originally been brought 

to the Kinneret via migrating water birds. 

E. drieschi from the Kinneret can be distinguished from other species of Eudiaptomus 

primarily by the P 5 appendages of the 2 sexes, and the male antenna. 

E. drieschi has a short endopod as opposed to the long, stout endopod of the male right P 5 

found in E. gracilis (Sars 1863) whose range includes most of Europe, Great Britain, and 

Russia. The endopod of the female right P 5 E. gracilis is covered with an apical fringe of 

hairs while that of E. drieschi is not. The distal corner process of the second exopod of male

left P 5 E. drieschi is blunter (rounded) with a sharp inner process. In E. gracilis, the distal 

process is sharper and the inner process has feather-like setae near the terminus. E. vulgaris 

(Schmeil 1898) which is found throughout Europe, Russia, central Asia, and northern Africa, 

has a hyaline membrane laying obliquely to the P 5 basipod, as well as a sharp projection from 

the outer distal corner of the first exopod. In E. drieschi, the hyaline membrane is parallel, 

and the projection from the outer distal corner of the first exopod is blunter. A newly 

described, closely related species, E. anatolicus n. sp., found in Turkey (Gunduz 1999), 

differs from E. drieschi in the absence of a “semicircular chitinous plate on the distal inner 

corner” of the coxopod of the male right P 5. 

Biometrics 

Kiefer (1935) described E. dreischi adult body length for males as 1.02-1.05 mm 

with a maximum 1.60 mm, and females as 1.17-1.20 mm with a maximum 

1.70 mm. The mean body length value (1.14mm) of adult male Eudiaptomus from Lake 

Kinneret is somewhat larger than the average values given by Kiefer (1935) but well 

within his range. It is known that body length of adult copepods can vary during a 

season, because temperature and food availability influence growth and adult body size. 

Elmore (1982) showed experimentally that body length of adult Diaptomus dorsalis 

(Marsh) increased at high food concentrations (10 x 10 4 cells /ml, Chlamydomonas). 

There is evidence that copepod body size decreases with increasing temperatures (Jacobs 

& Bouwhuis 1978, Kamps 1978, Hopcroft 1998, Gillooly 2000).

4.2 Ecological Implications of Development 

In copepod populations that have more than 1 generation per year, it is laborious to 

determine production values in situ. The presence of several generations at any one time 

makes it necessary to experimentally determine stage development times in the lab. The 

development cycles of calanoid and cyclopoid species have long been the subject of 

intense and varied studies (Gophen 1976, Ban 1991, 1992, 1992a, 1994, Chen 1993, 

Davis 1992, Durbin 1992). Knowledge of an organisms’ developmental history enables 

us to understand their population dynamics as well as intra-species relationships under 

natural conditions (Kawabata 1989, Atkinson 1991, Giangrande 1994, Kiorboe 1994, 

Toth 1996). Variations in life cycle patterns (sex ratios, P/B ratios, body size) may 

indicate adaptations to environmental changes such as predation pressure, food 

availability or abiotic factors like temperature and salinity (Allan 1976). Food type and 

quality as well as temperature and photo-periodicity affect the life span and stage 

development times of zooplankton species (Bogdon & McNaught 1975, Gophen 1976, 

Bergmans 1984, Santer 1994, Watson 1984, Burns & Hegarty 1994). A species’ life 

cycle may respond and adjust to seasonal differences in temperature and day-length 

(Hairston Jr. 1990, 1995, Hairston & Olds 1986). 

The instantaneous rate of change of the E. drieschi population in the Kinneret is 

small, which supports the observation that distinct cohorts cannot be distinguished from 

the weekly sampling series. The instantaneous birth rate is very similar to the 

instantaneous death rate (mortality), indicating the population is in a “steady state” for 

the period of time (approx. 6 months) it can be found in detectable numbers. 

It is worth noting that in Lake Skadar, Montenegro, E. drieschi exhibits rapid 

turnover and almost continuous reproduction and mortality, as it does in the Kinneret. 

However, no pattern of seasonality was observed. It occurs throughout the year with

peak abundance in October where water temperatures vary from 15- 18 0 C (Petkovic 

1981), not during winter/spring as in the Kinneret when water temperatures are low 

(16-20 0 C). 

Upon hatching from the egg, diaptomid copepods pass through 6 naupliar (NI – NVI) 

and 5 copepodite (CI – CV) stages during their development to adulthood. They undergo 

periods of intense metabolic activity prior to these molts (Carrillo 2001). Naupliar stage 

NI , (and in some species, NII & NIII ) is a non-feeding stage (Burns 1988, Hart 1990), 

and therefore more influenced by temperature than food concentration. These stages also 

suffer high mortality (Elmore 1983, Ban 1994, Kawabata 1995, Gillooly 2000). Each 

developmental stage shows a specific response to environmental conditions by its varied 

feeding habits, locomotion, vertical distribution, and rate of mortality. Determining the 

development, growth and survival of post-embryonic life stages is necessary to analyze 

the dynamics of the natural populations. Development times of diaptomid life stages 

have been shown to be temperature and food dependant (Kawabata 1989, Hart 1990, 

Ban 1994). Geiling (1972) found development times for Diaptomids varied as much as 

66.2 days at low temperatures, to 14.6 days at high temperatures. Hamberger (1987) 

found development time of E. graciloides from N I to adult to be 23 days at 21 0 C and 

42 days at 14.5 0 C. Similar development times were found for E. gracilis (P-Zankai 

1978). Similar to those studies, E. drieschi from the Kinneret also showed increasing 

development with temperature (12 days at 22 0 C and 33 days at 12 0 C from N I to adult). 

Gillooly (2000) states that generation time is related to both temperature and adult body 

mass. In a review of post-embryonic development duration of calanoid copepods, Hart 

(1990) found ratios of duration of copepodid development to duration of naupliar 

development (Dc/Dn) to favor slightly longer duration of the larger copepodid stages 

regardless of temperature. Knowledge of this relationship could aid in explaining

seasonal abundance or intra-specific interactions. The post-embryonic development 

times of the Kinneret population of E. drieschi are very similar, however there are 

differences in development times between stages. 

Ontogenetic development of E. drieschi in Lake Kinneret is similar to the patterns 

described in the literature for other diaptomids, and highly influenced by temperature. 

The early stages (NI-NIII) have relatively short development times, but development 

times are seen to increase to N IV. The stages that undergo the more complex changes 

(NVI & CIV) have slightly longer mean development times. That these development 

times are highly influenced by environmental parameters is reflected in the seasonal 

abundance and the changing P/B ratios. 

Production/Biomass Ratios 

Changes in the male/female sex ratios are also indicative of changes in population 

dynamics. Biased ratios, which are more the rule than the exception in freshwater, may 

be the result of changes in rates of development or mortality of the different sexes 

(Hairston et al. 1983). Ponyi (1982) found a sex ratio of 1:1.6 in favor of female E. 

gracilis in Lake Balaton at the start of their study period, which changed the following 

year to 1:1.1 in favor of males. Maly (1970) showed that selective predation on adult 

copepods caused skewed sex ratios. Although E. drieschi has been found in the guts of 

zooplanktivorous fish (Gophen 1978, Shapiro 1999) it is doubtful that selective 

predation is a causative factor in the dynamics of this organism in the Kinneret because 

of its low density. The Eudiaptomus population structure was found to favor females in 

1994, males from 1995-97, and a 1:1 sex ratio was seen in 1999. Males were found to 

develop slightly faster than females in the laboratory, which could account for their

higher numbers. The shift in sex ratio is another indication of the instability of the E. 

drieschi population in the Kinneret. 

Within the study period, the population density varied from 43 ind. l -1 in 1997, to 

distinguish resting eggs from subitaneous ones by the presence of a space between the 

embryo and the chorion in the subitaneous eggs. 

The resting eggs may also provide a means for dispersal as well as being an energy 

saving trait to remain in a specific location (Dahms 1995, Hairston Jr. 1996). Jarnagin et 

al. (2000) found that fish act as dispersing agents of diapausing invertebrate eggs in their 

movements between the pelagic and littoral zones of lakes. Viable resting eggs of E. 

drieschi were found in the gut of larval catfish (Clarias gariepinus) from the Kinneret, 

however their role in the dispersal of Eudiaptomus resting eggs has yet to be 

investigated. 

Many species of marine planktonic copepods have been shown to produce resting or 

diapause eggs as a long-term survival strategy (Marcus 1996). Such strategies are 

considered unusual for temperate climates that do not exhibit extreme seasonal 

fluctuations. However, examples from tropical and sub-tropical areas have been 

recorded. These species usually disappear from the water column for some months, but 

the populations recover from resting eggs in the sediment (Marcus 1989). Benthic 

resting eggs may be an important source of recruitment to the plankton. They do not 

utilize benthic food resources, but they may add a potential prey item for benthic 

consumers. 

E. drieschi in Lake Kinneret follows a seasonal pattern characteristic of subtropical 

diaptomid populations. They became very scarce in the water column throughout the 

summer/fall seasons, while the population has a higher density throughout the 

winter/spring. Subitaneous eggs are produced in Jan-Mar., then the first clutches of 

resting eggs are produced. In April-May the percentage of resting eggs increases to 

about 33% of all eggs produced. Throughout May-June, resting eggs make up 

approximately 50% of all eggs produced. During this period, the water temperature in 

the epilimnion is increasing (Fig. 6). It was found experimentally, that temperatures 

above 24 0 C are lethal to E. drieschi in the Kinneret., Although development rates are 

high at temperatures > 22 0 C, egg production is greatly reduced, thus bringing about the 

annual population decline. 

The source of the recovered winter/spring populations in the Kinneret are the resting 

eggs produced the previous season. Ban (1992) found viable eggs of the freshwater 

diaptomid, Eurytemora affinis (Poppe) distributed up to sediment depths of 10 cm., with 

the majority found in the upper 5 cm. Hatching of these eggs in the lab was inhibited by

covering them with a layer of sediment, which could explain the accumulation of viable 

eggs at greater sediment depths. This finding eliminates photoperiod as a cue for 

inducing or terminating diapause (Ban 1992, Ban & Minoda 1992, Hairston Jr. & 

Kearns 1995). The maximum sediment depth at which the resting eggs of E. drieschi in 

the Kinneret were found was 15 cm. Eggs were seen to be viable when induced to hatch 

in the laboratory, by removal from the sediments. All eggs did not hatch simultaneously, 

but over a period of weeks. It is assumed that this reflects the order in which they were 

laid down. 

Resting eggs that are covered by sediment will not hatch. Recent studies have shown 

that the accepted rate of sedimentation in the Kinneret (mean 0.5 cm./yr.) actually varies 

highly with location (Serruya 1978). Presence of eggs, coincides reasonably with the 

timing of their appearance among the pelagic lake zooplankton. Nishri et al. (1998) have 

successfully dated sediment layers using 137 Cs activity. They have shown that from the 

pelagic regions, (station A, 42 m depth), sedimentation rate is about 3-4 mm per year. 

Therefore it is reasonable to infer that resting eggs found at sediment depths of 9- 10 cm 

were deposited in the early ‘80’s (1982-1984). Sedimentation rate at sampling station F 

(20 m depth) is roughly 50 % higher than station A so that resting eggs found at depths 

of 10-12 cm were most likely deposited in the mid to late ‘80’s. Those eggs in the 

deeper sediment layers act as a stock of potential recruits to the planktonic population. 

Bioturbation may play a role in exposing the eggs lying under the water-sediment 

interface. Bottom feeding fishes or bubbles of gas (methane) may disturb the upper 

sediment layers, exposing the eggs and allowing them to hatch. 

4.4 Vertical Distribution 

The vertical diel migration of a zooplankton species should be differentiated from its 

ontogenetic vertical distribution. The species show a tendency to be found in deeper 

layers of the water column during the daylight hours, while their numbers are more 

evenly distributed at night. Kawabata (1995) found significant differences in vertical 

depth distributions between life stages of Eodiaptomus japonicus in Lake Biwa, Japan. 

E. japonicus ascended in the early naupliar stages (NI – NIII) and descended in the later 

stages (NIV – CII). This could be explained by the developmental changes in swimming

ability as copepods mature. Diaptomid nauplii have poor swimming ability, with no 

developed trunk appendages. Early copepodites have not yet developed the five pairs of 

swimming legs, thus are also poor swimmers compared to later copepodite stages and 

adults. 

There is no difference between the day and night vertical distribution of the naupliar 

stages of E. drieschi in the Kinneret, they remain more or less around the same depth (8- 

9 m). Copepodids were observed to inhabit similar depths to those of nauplii during the 

day, but were found at slightly shallower depths (5-6 m) throughout the night. Adults 

were distributed primarily at depths

4.5 Experimental Results 

4.5.1 Salinity 

The period 1970-1987 was characterized by a number of man-made changes in the 

Lake Kinneret ecosystem (Gophen 1992). The Degania dam at the southern end of the 

lake was built in 1932 and caused an overall increase of the water level. The National 

Water Carrier started pumping water from the lake in 1964 and also influences the water 

level. In 1965, salt-water diversion canal was constructed to aid in reducing the high 

concentrations of sodium chloride in the lake. Before the construction of the canal, 

chloride concentration varied from 380-400 ppm Cl - . The operation of the canal and the 

heavy floods of 1968-69 caused a decline in the amount of salt in the Kinneret (stock 

and concentration) to an annual average (1988) of 208 ppm Cl - . Salinity, measured as 

Cl - concentration, at the start of this study (1996) was 218 ppm Cl - . The lake salinity 

has recently increased due to three consecutive drought years (1999- 2001) and a 

negative water budget during the summers. Because of the low water level, the saline 

springs are not being diverted through the canal and contribute about 5% to the 

increasing lake salinity. 

Laboratory experiments in this study showed adult E. drieschi reared in chloride 

concentrations >225 ppm (lake concentration during experimental period) had lower 

percent survival than those reared in

4.5.2 Temperature 

Temperature has both direct and indirect effects on zooplankton growth and 

development (Geiling & Campbell 1972, Herzig 1983, Edgar 1990, 

Ban 1992, 1994). An organisms’ behavior, development, reproduction, as well as the 

dynamics of an entire population may be directly influenced by changes in temperature. 

Zooplankton community responses to thermal dynamics are highly varied even among 

co-occurring species. Moore et al. (1996) reviewed effects of temperature on the 

population dynamics of freshwater zooplankton. They observed that in many temperate 

lakes, survivorship declines at temperatures greater than 25 0 C. They also observed that 

thermal responses are varied among co-occurring species and among cohorts as well. 

It appears that under sufficient food regimes, temperature is a major influence on 

stage development duration in E. drieschi in Lake Kinneret. It has become more 

apparent from the literature that differences exist in pre and post embryonic 

development times as well as inter-species stage duration from different bodies of water 

(Jacobs & Bouhuis 1979, Herzig 1983, Hart 1994, Calbet et al. 2000). Differences in 

development rates of the same species (E. gracilis) from different locations were 

suggested to be influenced mainly by temperature (Edgar 1990). Therefore, 

measurements of a specific species may only be applicable to the water body in which it 

is found. 

Klein Breteler et al. (1994) examined the development time of five copepod species. 

He found the duration of the different life stages was not constant, but tended to increase 

slightly. The duration of the later copepodite stages was generally longer than the 

younger stages. This is compatible with the generalizations of Landry (1983) and with 

the results of this study. When discussing post-embryonic development of several 

species of Eudiaptomus, Jacobs (1979) noted differences in the development times of 

the same species from different locations. Calbet et al. (2000) showed that at some 

specific sampling locations, juvenile and adult copepod growth rates were similar, while

at others, adult growth rates were higher. Comparison of pre-embryonic development 

times of tropical and sub-tropical diaptomids by Elmore (1983) showed differences in 

egg development most significant at high temperatures. 

Experiments showed development times and stage duration of E. drieschi at low 

temperatures were significantly different from the other treatments. Average 

development times at optimum temperatures, however, were seen to be comparable. 

Lake Kinneret rarely reaches an average temperature of 12 0 C in the epilimnion, 

therefore it is reasonable to assume that E. drieschi would not develop naturally at this 

temperature. The number of egg-bearing females begins to increase when the lake 

reaches 15 0 C, with maximum reproduction occurring at 18 -20 0 C. When the temperature 

rises above 22 0 C, the number of egg-bearing females decreases. 

The extremely high mortality seen in the lab at 24 0 C, and slow growth rates at 12 0 C 

is indicative of the thermal- sensitivity of E. drieschi in the Kinneret. Various authors 

have found that post-embryonic development rates are highly variable at higher 

temperatures (Huntly & Lopez 1992, Ban 1994). E. vulgaris (Schmeil 1896), a cold 

water species, experienced decreased rate of development at higher temperatures. This 

was attributed to thermal stress at temperatures not usually experienced in the wild 

(Kamps 1978). 

Indirectly, temperature could affect changes in the structure of the algae communities 

which provide food for the zooplankton. Rates of predation by zooplanktivorous fish are 

also influenced by temperature. Thus, investigating the appearance of a species in a 

previously unrecorded area where the temperature regime differs from its place of origin 

can be of significant interest and lead to understanding the evolutionary factors which 

govern species adaptations to new environments.

4.5.3 Food 

Calanoid copepods in general, are versatile feeders. They are able to adapt to sudden 

changes in available particle size and abundance (Bogdan 1975, Burns 1994, Dumont 

1994, DeMott 1995). Food has been assumed to limit production in copepods by 

influencing growth and fecundity (Checkley 1980, Butler 1994). Changes in nutrient 

levels and community structure of phytoplankton assemblages, can result is variation in 

food quality and quantity. Although naupliar and copepodid stages need a reliable food 

source for natural development, it has been suggested that naupliar growth is less 

influenced by food supply (Hart 1990). Female reproduction and adult body size may 

also be influenced by food availability and quality. 

The phytoplankton population in lakes inhabited by Eudiaptomus species are 

comprised of Chlamydomonas and Rhodomonas species, among others (Beeton 1981, 

Zankai 1991, Santer 1994), and these genera are present in the Kinneret as well. 

Although experiments carried out in this study showed that E. drieschi does poorly in 

food concentrations less than 7,000 cells ml -1 , nanoplankton concentrations do not drop 

below 9.8 x 10 3 cells ml –1 in the Kinneret, suggesting that E. drieschi is not food limited 

in the Kinneret.

5. Conclusions. The Salinity Filter in an Old Lake. 

Lake Kinneret is among the early Pleistocene ancient lakes of the world. It is 

characterized by higher species diversity in the littoral and benthos that is in contrast to 

a simpler less diversified pelagic community structure. The open water is considered too 

homogeneous an environment to allow a high species diversity. Also the number of 

endemic species is relatively small in the Kinneret in comparison to other pre-glacial 

lakes. Tchernov (1975) indicates that the small number of species found today in the 

Kinneret , may be a result of geological events that occurred during the Pleistocene 

along the Jordan Rift Valley, however Por (1963) attributes it to the oligohaline nature 

of the lake. A number of marine relict species among the lake fauna may be explained as 

survivors of the receding Pliocene Mediterranean. Representitives of the Mollusca and 

Harpacticoida, are found to be related to species from the Anatolian lacustrine basin 

(Lake Egerdir, Turkey), which suggests a “natural link” for species distribution (Por 

1963). 

Over the years, there has been no continous survey of the species biodiversity of 

the lake. According to Komarovsky (1959), no changes had occurred “in the 

composition of the plankton during a period of over sixty years”. Komarovsky himself 

reported on the presence of a single female specimen Moina rectirostris in material 

collected from 1948-49 which had not been found by other investigators and was 

considered “accidental”. Bromley (1993) has identified 4 species of Moina in Israel, of 

which Moina micrura dubia (Richard) is now recognized as a regular constituent of the 

Lake Kinneret cladocera. Daphnia lumholtzi (Sars),was recorded in the lake in the years 

prior to and including 1956. D. lumholtzi was previously known from African Rift 

valley lakes (Lake Albert) with high salanities. Throughout the period (prior to the 

1950’s) that D. lumholtzi was found in the Kinnerert, average salinity was >300 ppm

chloride. Between 1955-69, salinity varied from 350 ppm, to 250 ppm Cl - . Gophen 

examined material collected in 1958-1960 and did not find D. lumholtzi . Subsequent 

studies (Por 1968, Gophen 1978) were also unsuccessful. Ther dissappearence of D. 

lumholtzi and the incorporation of M. micrura dubia to the Kinneret plankton, are 

indications of the changes undergone by the system. 

Despite the slightly oligohaline nature of the lake, the Kinneret, overall, has 

almost no seasonal fluctuations of salinity. However, the Kinneret system has undergone 

a series of temporal modifications, some man-made and some natural, which have 

resulted in alterations in its biological regime. These changes may have contributed to a 

temporary variation in the “biological filter barrier” and creating an environment 

suitable for Eudiaptomus drieschi to successfully establish itself as a new member of the 

pelagic fauna of Lake Kinneret. 

The fact that an organism reaches the lake does not necessarily ensure its 

incorporation into the lake ecosystem (Williamson 1996). It would require the 

breakdown or alteration of the natural “fauna filters” i.e.: salinity, temperature, ionic 

composition in the system to allow an organism to “invade”. 

Since an invading organism is defined as one that is found anywhere outside its 

previous range (Williamson 1996), E. drieschi may be seen to have successfully invaded 

the Kinneret open water system during the period when chloride concentrations were 

low. It adapted to the extreme conditions by increasing production of resting eggs as the 

lake temperature increased. This is the first record of E. drieschi in Israel, as well as the 

first report of a diaptomid species becoming established in Lake Kinneret. Previous 

reports of the diaptomid E. gracilis in the lake may be the result of erroneous 

identification.

E. drieschi has not been recorded from the Hula Reserve, from the waters of the 

partially re-flooded Hula Lake (Lake Agmon), (Por, pers. comm.), nor has it been found 

in any other water body in Israel where diaptomid species are present. The relatively 

young age of the Kinneret bottom sediments (Nishri et al 1998) in which resting eggs 

are found, indicate the recent invasion of this organism to the pelagic waters of the lake 

(early to mid 1980’s). 

A potential vector for resting egg transport via the gut contents of fish is likely, 

as the resting eggs have no spines or hooks on the outer surface when examined with a 

scanning electron microscope. This would tend to rule out passive transport by air, as a 

means of dispersion. Viable resting eggs were found in the gut of larval catfish (Clarias 

gariepinus) from the lake. It is conceivable that E. drieschi may have been introduced 

into the lake by migrating, piscivorous birds from Turkey or Cyprus. 

Although found throughout the year in other locations, e.g.: Lake Skadar 

(Scutari) in Montenegro (Petkovic 1981) and Lake Poyraz and L. Egerdir, Anatolia 

(Gunguz 1998), it disappears from the water colum in the Kinneret during the summer 

and early fall. E. drieschi appears to have adapted to the environment fo Lake Kinnerert 

by evolving a life history which removres it from the water column during periods of 

high temperature. This is the first mention of resting eggs in the copepod fauna of Lake 

Kinneret. 

Salinity, (chloride concentration) decreased from 400 ppm in the late 1960’s to 

208 ppm in the late 1980’s. This reduction of salinity concentration is considered to be 

the primary releasing factor in the establishment of E. drieschi throughout the lake. 

Salinity has begun to increase recently due to successive drought years, ans is currently 

(2001) 380 ppm Cl - . E. drieschi is presently not encountered in the Lake.

This study offered the rare (and fortuitous) opportunity to witness a temporary 

change in the animal realm of Lake Kinneret, induced by changes in the salinity regime. 

Laboratory studies confirmed the sensitivity and negative response of E. drieschi to 

abrupt changes in salinity concentrations. 

The very restricted seasonal pattern of E. drieschi in the lake provides a 

sensitive indicator for future changes in the temperature regime of the Lake. The 

temperature sensitivity of E. drieschi may serve as a yardstick for overall global 

warming-by signaling warming of Lake Kinneret.

References 

Allan, J.D. 1976. Life History Patterns in Zooplankton. American Naturalist 

110: 165-180. 

Allan, D.J., C.E. Goulden. 1980. Some aspects of reproductive variation 

among freshwater zooplankton. Pages 388-410, in: Kerfoot, W.C., Evolution 

and Ecology of Zooplankton Communities. 3. University Press of New 

Hampshire. Hanover. 

Atkinson, A. 1991. Life cycles of Calanoides acutus, Calanus simillimus and 

Rhincalanus gigas (Copepoda: Calanoida) within the Scotia Sea. Marine 

Biology 109: 79-91. 

Azoulay, B. 1999. The occurrence of the diaptomid Eudiaptomus drieschi 

(Poppe & Mrazek 1895) in Lake Kinneret, Israel. Abstract, 7 th International 

Conference on Copepoda, Curitiba, Brazil, 25 –31 July 1999, p.53. 

Ban, S. 1992a. Effects of photoperiod, temperature, and population density 

on induction of diapause egg production in Eurytemora affinis 

(Copepda:Calanoida) in Lake Ohnuma, Hokkaido, Japan. Journal Crustacean 

Biology 12: 361-367. 

Ban, S. 1992b. Seasonal distribution, abundance and viability of diapause of 

Eurytemora affinis (Copepoda: Calanoida) in the sediment of Lake Ohnuma, 

Hokkaido. Bulletin Plankton Society Japan 39: 41-48. 

Ban, S. 1994. Effect of temperature and food concentration on postembryonic 

development, egg production and adult body size of calanoid 

copepod Eurytemora affinis. Journal of Plankton Research 16: 721-735. 

Ban, S. and Minoda, T. 1991. The effect of temperature on the development 

and hatching of diapause and subitaneous eggs in Eurytemora affinis 

(Copepoda:Calanoida) in Lake Ohnuma, Hokkaido, Japan. Bulletin of the 

Plankton Society of Japan, Spec. Vol.: 299-308. 

Ban, S. and Minoda, T. 1992. Hatching of diapause eggs of Eurytemora 

affinis (Copepoda: Calanoida) collected from lake-bottom sediments. Journal 

Crustacean Biology. 12: 51-56. 

Ban, S. and Minoda, T. 1994. Induction of diapause egg production in 

Eurytemora affinis by their own metabolites. Hydrobiologia 292/293: 185- 

189. 

Bautista, B., Harris, R.P., Rodriguez, V., and Guerrero, F. 1994. Temporal 

variability in copepod fecundity during two different spring bloom periods in 

coastal waters off Plymouth (SW England). Journal of Plankton Research 16: 

1367-1377.

Beeton, A. M. (1981) General introduction. The Biota and Limnology of Lake 

Skadar (ed. Karaman, G. S. & Beeton, A. M.), pp. 15-17. University of 

"Veljko Vlahovic", Smithsonian Institution of Washington, and Centre for 

Great Lakes Studies/University of Wisconsin, Titograd. 

Belmonte, G. 1992. Diapause egg production in Acartia (Paracartia) 

latisetosa (Crustacea, Copepoda, Calanoida). Boll. Zool. 59: 363-366. 

Belmonte, G. and Puce, M. 1994. Morphological aspects of subitaneous and 

resting eggs from Acartia josephinae (Calanoida). Hydrobiologia 292/293: 

131-135. 

Berberovic, R., Bikar, K., Geller, W. 1990. Seasonal variability of the 

embrionic development time of three planktonic crustaceans: dependence on 

temperature, adult size, and egg weight. Hydrobiologia 203: 127-136. 

Bergmans, M. 1984. Life History adaptation to demographic regime in 

laboratory-cultured Tisbe furcata (Copepoda, Harpacticoida). Evolution 38: 

292-299. 

Berman, T., Yacobi, Y.Z. and Pollingher, U. 1992. Lake Kinneret 

phytoplankton: stability and variability during twenty tears (1970-1989). 

Aquatic Sciences 54: 104-127. 

Bird, D.F. and T-Prairie, Y. 1985. Practical guidelines for the use of 

zooplankton length-weigth regression equations. Journal of Plankton 

Research 7: 955-960. 

Bodenheimer, F.S. 1935. Animal Life in Palestine. L. Mayer. Jerusalem. 506 

p. 

Bogdan, K.G. and McNaught, D.C. 1975. Selective feeding by Diaptomus 

and Daphnia. Verh. Internat. Vernat. Limnol. 19: 2935-2942. 

Borutsky, E.V., Stepanova, L.A. and Kos, M.S. 1991. Key to Calanoida of 

fresh waters of the USSR. "Nauka". St. Petersburg. p.503 , (in Russian). 

Bromley, H. J. 1993. A checklist of the Cladocera of Israel and Eastern Sinai. 

Hydrobiologia 257: 21-28. 

Burns, C.W. and Hegarty, B. 1994. Diet selection by copepods in the 

presence of cyanobacteria Journal of Plankton Research. 16: 1671-1690. 

Calbet, A, Trepat, I.., Arir, L. 2000. Naupliar growth vs egg production in the 

calanoid copepod Centropages typicus. Journal of Plankton Research. 22 (7): 

1393-1401.

Carrillo, P., M. Villar-Argaiz, J.M. Medina-Sanchez. 2001. Relationship 

between N:P ratio and growth rate during the life cycle of calaniod copepods: 

An in situ measurement. Journal of Plankton Research. 23:5, 537-547. 

Castro-Longoria, E. and Williams, J.A. 1996. First report of the presence of 

Acartia margalefi (Copepoda: Calanoida) in Southampton Water and Horsea 

Lake, UK. Journal of Plankton Research 18: 567-575. 

Checkley, D.M. 1980. Food limitation of egg production by a marine, 

planktonic copepod in the sea off southern California. Limnology and 

Oceanography 26: 991-998. 

Checkley Jr., D.M. 1980. The egg production of a marine planktonic 

copepod in relation to its food supply: Laboratory studies. Limnology and 


Chen, C.Y. and Folt, C.L. 1993. Measures of food quality as demographic 

predictors in freshwater copepods. Journal of Plankton Research. 15: 1247- 

1261. 

Cooney, J.D. and Gehrs, C.W. 1980. The relationship between egg size and 

nauplier size in the calanoid copepod Diaptomus clavipes Schacht. Limnology 

and Oceanography 25: 549-552. 

Cowles, T.J. and Strickler, J.R. 1983. Characterization of feeding activity 

patterns in the planktonic copepod Centropages typicus Kroyer under various 

food conditions. Limnology and Oceanography 28: 106-115. 

Culver, D.A., Boucherle, M.M., Bean, D.J., and Fletcher, J.W. 1985. 

Biomass of Freshwater Crustacean Zoooplankton from Length-Weight 

Regressions. Canadian Journal of Fisheries and Aquatic Science 42: 1380- 

1390. 

Dahms, H. U. 1985. Dormancy in the Copopoda – an overview. 

Hydrobiologia 306: 119-211. 

Davis, M.S. and Alatalo, P. 1992. Effects of constant and intermittent food 

supply on life-history parameters in a marine copepod. Limnology and 


Damian-Georgescu, Andriana.1966. Fauna Republlicii Socialiste Romania. 

Crustacea Copepoda, Vol. IV(8). Calanoida. Academiei Republicii Socialiste 

Romania. Pp. 130. (in Rumanian). 

De Meester, L. and Vyverman, W. 1997. Diurnal residence of the larger 

stages of the calanoid copepod Acartia tonsa in the anoxic monimolimnion of 

a tropical meromictic lake in New Guinea. Journal of Plankton Research 19: 

435-447.

DeFrenza, J., Kirner, R.J., Maly, E.J., and Leeuwen, H.C.v. 1986. The 

relationships of sex size ratio and season to mating intensity in some calanoid 

copepods. Limnology and Oceanography 31: 491-496. 

DeMott, W.R. 1995. Optimal foraging by a suspension-feeding copepod: 

responses to short-term and seasonal variation in food resources. Limnology 


DeStasio Jr, B.T. 1993. Diel vertical and horizontal migration by 

zooplankton: Population budgets and the diurnal deficit. Bulletin of Marine 

Science 53: 44-64. 

DeStasio Jr., B.T. 1989. The seed bank of a freshwater crustacean: 

copepodology for the plant ecologist. Ecology 70: 1377-1389. 

Dimentman, C. and Por, F.D. 1985. Diaptomidae (Copepoda, Calanoida) of 

Israel and Northern Sinai. Hydrobiologia 127: 89-95. 

Downing, J.A., F.H. Rigler, 1984. A manual on methods for the assessment of 

secondary productivity in freshwaters. Blackwell Scientific Pub. Oxford,2 nd 

ed. Pp. 501. 

Dumont, H.J. 1994. Ancient lakes have simplified pelagic food webs. Arch. 

Hydrobiol. Beih. Ergebn. Limnol. 44, pp 223-234. 

Durbin, E.G. and Durbin, A.G. 1992a. Effects of temperature and food 

abundance on grazing and short-term weight change in the marine copepod 

Acartia hudsonica Limnology and Oceanography 37: 361-378. 

Durbin, A.G. and Durbin, E.G. 1992b. Seasonal changes in size frequency 

distribution and estimated age in the marine copepod Acartia hudsonica 

during a winter-spring diatom bloom in Narragansett Bay. Limnology and 


Durbin, E.G., Durbin, A.G. and Campbell, R.G. 1992. Body size and egg 

production in the marine copepod Acartia hudsonica during a winter-spring 

diatom bloom in Narragansett Bay. Limnology and Oceanography 37: 342- 

360. 

Durbin, E.G., Durbin, A.G., Smayda, T.J., and Verity, P.G. 1983. Food 

limitation of production by adult Acartia tonsa in Narragansett Bay, Rhode 

Island Limnology and Oceanography 28: 1199-1213. 

Eckert, W., B.Shteinman, Anis, A., Hadas, O., Ostrovsky, I., and Gophen, M. 

1998. The evolution of long internal waves in Lake Kinneret: implication for 

chemical stratification, biological dynamics, and large scale particle transport. 

Internal report for Israel Oceanographic & Limnological Research, The Yigal 

Allon Kinneret Limnological Laboratory. 29 p.

Edgar, N.B. and Green, J.D. 1994. Calanoid copepod grazing on 

phytoplankton: seasonal experiments on natural communities. Hydrobiologia 

273: 147-161. 

Edmondson, W.T., Comita, G.W. and Anderson, G.C. 1962. Reproductive 

rate of copepods in nature and its relation to phytoplankton population. 

Ecology 43: 625-634. 

Engstrom, D.R. 1999. Population biology of a failed invasion: 

Paleolimnology of Daphnia exilis in upstate New York. Limnology and 

Oceanography. 44: 477-486. 

Elgmork, K. 1980. Evolutionary aspects of Diapause in freshwater copepods. 

Pages 411-417, in: Kerfoot, W.C., Evolution and Ecology of Zooplankton 

Communities. 3. University Press of New Hampshire. Hanover. 

Elmore, J.L. 1983. Factors influencing Diaptomus distributions: An 

experimental study in subtropical Florida. Limnology and Oceanography 28: 

522-532. 

Evans, C.A., O'Reilly, J.E. and Thomas, J.P. 1987. A Handbook for the 

measurement of Chlorophyll a, and primary production. Texas A&M 

University. College Station, Texas USA. 114 p. 

Gaedke, U. 1992. The size distribution of plankton biomass in a large lake 

and its seasonal variability. Limnology and Oceanography 37: 1202-1220. 

Geddes, M.C. and Cole, G.A. 1981. Variation in sexual size differention in 

North American diaptomids (Copepoda: Calanoida): Does variation in the 

degree of dimorphism have ecological significance? Limnology and 


Geiling, W.T. and Campbell, R.S. 1972. The effect of temperature on the 

development rate of the major life stages of Diaptomus pallidus Herrick. 

Limnology and Oceanography 17: 304-307. 

George, D.G., I.J. Winfield, 2000. Factors influencing the spatial distribution 

of zooplankton and fish in Loch Ness, U.K. Freshwater Biology 43:4, 557- 

570. 

Gillooly 2000. Effect of body size and temperature on generation time in 

zooplankton. Journal of Plankton Research. 22:2, 241-251. 

Gitay, A. 1968. Preliminary data on the ecology of the level-bottom Fauna of 

Lake Tiberias. Israel Journal of Zoology 17, 81-96. 

Gophen, M. 1976. Temperature effect on lifespan, metabolism, and 

development time of Mesocyclops leuckarti (Claus). Oecologia 25: 271-277.

Gophen, M. 1977. Food and feeding habits of Mesocyclops leuckarti (Claus) 

in Lake Kinneret (Israel). Freshwater Biology 7: 513-518. 

Gophen, M. 1978. Zooplankton., Lake Kinneret, in Monographiae 

Biological. 32. C. Serruya, ed. Junk. The Hague. Pages 297-311 

Gophen, M. 1979. Extinction of Daphnia lumholtzi (Sars) in Lake Kinneret 

(Israel). Aquaculture 16: 67-71. 

Gophen, M. 1984. The impact of zooplankton status on the management of 

Lake Kinneret (Israel). Hydrobiologia 113: 249-258. 

Gophen, M. 1989. Utilization and water quality management of Lake 

Kinneret, Israel. Toxicity Assessment: An International Journal 4: 353-362. 

Gophen, M. and Paz, J.D. 1992. Decreased salinity effects in Lake Kinneret 

(Israel). Hydrobiologia 228: 231-237. 

Gophen, M. and Pollinger, U. 1985. Relationships between food availability 

fish predation and the abundance of the herbivorous zooplankton community 

in Lake Kinneret. Arch. Hydrobiol. Beih. 21: 397-405. 

Gophen, M., Serruya, S. and Spataru, P. 1990. Zooplankton community 

changes in Lake Kinneret (Israel) during 1969-1985. Hydrobiologia 191: 39- 

46. 

Grad, G. and Maly, E.J. 1988. Sex size ratios and their influence on mating 

success in a calanoid copepod. Limnology and Oceanography 33: 1629-1634. 

Greene, C.H. 1988. Foraging tactics and prey-selection patterns of 

omnivorous and carnivorous calanoid copepods. Hydrobiologia 167/168: 

295-302. 

Guerrero, F., Rodriguez, V. 1998. Existence and significance of Acartia grani 

resting eggs (Copepoda: Calanoida) in sediments of a coastal station in the 

Alboran Sea (SE Spain). Journal of Plankton Research. 20, 305-314. 

Gunduz, E. 1998. Eudiaptomus anatolicus n.sp. (Copepoda: Calanoida) from 

Turkey. Hydrobiologia 368: 193-199. 

Hairston Jr., N.G. 1980. On the diel variation of copepod pigmentation. 


Hairston Jr., N.G. 1987. Diapause as a predator-avoidance adaptation. in: 

Kerfoot, W.C. and Sih, A., Predation: Direct and Indirect Impacts on Aquatic 

Communities , Pages 281-290.

Hairston Jr., N.G. 1988. Interannual variation in seasonal predation: Its 

origin and ecological importance. Limnology and Oceanography 33: 1245- 

1253. 

Hairston Jr., N.G., Walton, W.E. and Li, K.T. 1983. The causes and 

consequences of sex-specific mortality in a freshwater copepod. Limnology 


Hairston Jr., N.G. and Munns, W.R. 1984. The timing of copepod diapause 

as an evolutionarily stable strategy. American Naturalist 123: 733-751. 

Hairston Jr., N.G. and Olds, E.J. 1984. Population differences in the timing 

of diapause: adaption in a spatially heterogeneous environment. Oecologia 

(Berlin) 61: 42-48. 

Hairston Jr., N.G., Olds, E.J. and Jr, W.R.M. 1985. Bet-hedging and 

environmentally cued diapause strategies of diaptomid copepods. Verh 

Internat Verein Limnol 22: 3170-3177. 

Hairston Jr., N.G. and Olds, E.J. 1986. Partial photoperiodic control of 

diapause in three populations of the freshwater copepod Diaptomus 

sanguineus. Biological Bulletin 171: 135-142. 

Hairston Jr., N.G. and Walton, W.E. 1986. Rapid evolution of a life history 

trait. Proceedings of the National Academy of Science 83. Cornell 

University. USA in: Edmondson, W.T.,. Pp. 4831-4833. 

Hairston Jr., N.G., Dillon, T.A. and Jr, B.T.D.S. 1990. A field test for the 

cues of diapause in a freshwater copepod. Ecology 71: 2218-2223. 

Hairston, Jr., N. G., R.A.Van Brunt,. 1994. Diapause dynamics of two 

diaptomid copepod species in a large lake. Hydrobiologia 292/293: 209-218. 

Hairston Jr., N.G. and Kearns, C.M. 1995. The interaction of photoperiod 

and temperature in diapause timing: A copepod example. Biological Bulletin 

189: 42-48. 

Hairston Jr., N.G., R.A.Van Brunt, C.M Kearns, D.R. Engstrom. 1995. Age 

and survivorship of diapausing eggs in a sediment egg bank. Ecology 76: 

1706-1711. 

Hairston Jr., N.G. and Caceres, C.E. 1996. Distribution of crustacean 

diapause: micro- and macroevolutionary pattern and process. Ecology 320: 

27-44. 

Hambright, K.D. and Friedman, S. 1994. A computer-assisted plankton 

analysis system for the Macintosh. Fisheries 19 : 12, 6-8.

Hanazato, T. and Yasuno, M. 1989. Influence of overwintering Daphnia on 

spring zooplankton communities: An Experimental study. Ecological 

Research 4: 323-338. 

Haney, J. F., D.J. Hall (1972). Sugar - coated Daphnia: A preservation technique for 

Cladocera. Limnology and Oceanography. 18: 331 – 333. 

Harris, J.R.W. 1983. The development and growth of Calanus copepodite. 


Hart, R. C., 1990. Copepod post-embryonic durations: pattern, conformity, 

and predictability. The realities of isochronal and equiportional development, 

and trends in the copepod-naupliar duration ratio. Hydrobiologia 206: 175- 

206. 

Hart, R.C. 1991. Food and suspended sediment influences on the naupliar 

and copepodid durations of freshwater copepods: comparative studies on 

Tropodiaptomus and Metediaptomus. Hydrobiologia 272: 77-86. 

Hart, R.C. 1994. Equiproportional temperature-duration responses and 

thermal influences on distributions and species switching in the copepods 

Metadiaptomus meridianus and Tropodiaptomus spectabilis. Hydrobiologia 

272: 163-183. 

Hart, R.C. and Rayner, N.A. 1994. Temperature-related distributions of 

Metadiaptomus and Tropodiaptomus (Copepoda: Calanoida), particularly in 

southern Africa. Hydrobiologia 272: 77-86. 

Hart, R.C. and Santer, B. 1994. Nutritional suitability of some uni-algal diets 

for freshwater calanoids: unexpected inadequacies of commonly used edible 

greens and others. Hydrobiologia 31: 109-116. 

Hartline, D.K., Lenz, P.H. and Herren, C.M. 1996. Physiological and 

Behavioral Studies of Escape Responses in Calanoid Copepods. Marine and 

Freshwater Behavioral Physiology 27: 199-212. 

Hayward, T.L. 1981. Mating and the depth distribution of an oceanic 

copepod. Limnology and Oceanography 26: 374-377. 

Herzig, A., 1983. The ecological significance of the relationship between 

temperature and duration of embrionic development in planktonic freshwater 

copepods. Hydrobiologia 100,65-91. 

Hopcroft R. R. and Roff, J.C. 1998a. Zooplankton growth rates: the 

influence of female size and resources on egg production of tropical marine 

copepods. Marine Biology 132: 79-86. 

Hopcroft, R.R. and Roff, J.C. 1998b. Zooplankton growth rates: the 

influence of size in nauplii of tropical marine copepods. Marine Biology 132: 

87-96.

Hopcroft, R.R., Roff, J.C. and Lombard, D. 1998. Production of tropical 

copepods in Kingston Harbour, Jamaica: the importance of small species. 

Marine Biology 130: 593-604. 

Hopcroft R. R., Roff, J.C., Webber, M.K., and Witt, J.D.S. 1998. 

Zooplankton growth rates: the influence of size and resources in tropical 

marine copepodites. Marine Biology 132: 67-77. 

Hutchinson, G.E. 1967. A Treatise on Limnology. Wiley and Sons, Inc. 

1115 p. 

Ianora, A. and Poulet, S.A. 1993. Egg viability in the copepod Temora 

stylifera. Limnology and Oceanography. 38: 1615-1626. 

Jarnagin, S.T., Swan, B.K., Kerfoot, W.C. 2000. Fish as vectors in the dispersal of 

Bythotrephes cederstroemi: diapausing eggs survive passage through the gut. 

Freshwater Biology 43 (4), 579-589. 

Jacobs, R.P.W.M., Bouwhuis, A.M.J., 1979. The year cycle of Eudiaptomus vulgaris in 

a small acid water body during 1973. Development in the natural habitat and 

relationships between temperature and duration of development stages. 

Hydrobiologia,64:1,17-36. 

Jersabek, C.D. and Schabetsberger, R. 1995. Resting egg prodution and 

oviducal cycling in two sympatric species of alpine diaptomids (Copepoda: 

Calanoida) in relation to temperature and food availability. Journal of 

Plankton Research. 17: 2049-2078. 

John, H.-C., Mittelstaedt, E. and Schulz, K. 1998. The boundary circulation 

along the European continental slope as transport vehicle for two calanoid 

copepods in the Bay of Biscay. Oceanologica Acta 21: 307-318. 

J¢nasd¢ttir, S.H. 1994. Effects of food quality on the reproductive success 

of Acartia tonsa and Acartia hudsonica: laboratory observations. Marine 

Biology 121: 67-81. 

Kamps, D.M 1978. The effect of temperature on the development time and brood size of 

Diaptomus pallidus Herrick. Hydrobiologia,61:1,75-80. 

Kawabata, Keiichi. 1989. Natural development time of Eodiaptomus 

japonicus (Copepoda: Calanoida) in Lake Biwa. Journal of Plankton 

Research., 11(6), 1261 – 1272. 

Katajisto, T. 1996. Copepod eggs survive a decade in the sediments of the 

Baltic Sea. Hydrobiologia 320: 153-159.

Kawabata, K. 1989. Natural development time of Eodiaptomus japonicus 

(Copepoda: Calanoida) in Lake Biwa. Journal of Plankton Research 11: 

1261-1272. 

Kawabata, K. 1995. Ontogenetic niches of a planktonic copepod in Lake 

Biwa studied on a fine temporal scale. Journal of Plankton Research 10: 207- 

215. 

Kiefer, F. 1968. Versuch einer revision der gattung Eudiaptomus Kiefer 

(Copepoda, Calanoida). Memorie dell’Istituto Italiano di Idrobiologia 24: 9- 

160. 

Kimmerer, W.J. and McKinnon, A.D. 1987. Growth, mortality, and 

secondary production of the copepod Acartia tranteri in Westernport Bay, 

Australia. Limnology and Oceanography 32: 14-28. 

Kiorboe, T. and Sabatini, M. 1994. Reproductive and life cycle strategies in 

egg-carrying cyclopoid and free-spawning copepods. Journal of Plankton 

Research. 16: 1353-1366. 

Klein Breteler, W.C.M., Schogt, N., van der Meer, J. 1994. The duration of 

copepod life stages estimated from stage-frequency data. Journal of Plankton 

Research.,16(8), 1039-1057. 

Kleppel, G.S. and Burkart, C.A. 1995. Egg production and the nutritional 

environment of Acartia tonsa: the role of food quality in copepod nutrition. 

ICES Journal of Marine Science 52: 297-304. 

Koehl, M.A.R. and Strickler, J.R. 1981. Copepod feeding currents: Food 

capture at low Reynolds number Limnology and Oceanography 26: 1062- 

1073. 

Komarovsky, B. 1959. The plankton of Lake Tiberias., in: Bulletin of 

Research Council of Israel. B8. 65-96 

Landry, M.R. 1983. The development of marine calanoid copepods with 

comment on the isochronal rule. Limnology and Oceanography 28: 614-624. 

Landry, M.R., Hassett, R.P., Fagerness, V., Downs, J., and Lorenzen, C.J. 

1984. Effect of food acclimation on assimilation efficiency of Calanus 

pacificus. Limnology and Oceanography 29: 361-364. 

Lawrence, S.G., Malley, D.F., Findlay, W.J., MacIver, M.A., and Delbaere, 

I.L. 1987. Method for estimating dry weight of freshwater planktonic 

crustaceans from measures of length and shape. Canadian Journal of 

Fisheries and Aquatic Science 44: 264-274. 

Lessells, C.M. 1991. Chapt. 2: The evolution of life histories. Pages 33-69, 

in: J.R., K. and N.B., D., Behavioural Ecology, An Evolutionary Approach. 

Blackwell Scientific.

Lohner, L., Jr, N.G.H. and Schaffner, W. 1990. A method for distinguishing 

subitaneous and diapausing eggs in preserved samples of the calanoid 

copepod genus Diaptomus. Limnology and Oceanography 35: 763-767. 

Lynch, M. 1983. Estimation of size-specific mortality rates in zooplankton 

populations by periodic sampling. Limnology and Oceanography 28: 533-545. 

Maly, E.J. 1973a. Density, size, and clutch of two high altitude diaptomid 

copepods. Limnology and Oceanography 18: 840-848. 

Maly, E.J. 1983b. Some further observations on diaptomid body size and 

clutch size relationships. Limnology and Oceanography 28: 148-152. 

Marcus, N.H. 1996. Ecological and evolutionary significance of resting eggs 

in marine copepods: past, present, and future studies. Hydrobiologia 320: 141- 

152. 

Marcus, N.H. and Lutz, R.V. 1994. Effects of anoxia on the viability of 

subitaneous eggs of planktonic copepods. Marine Biology 121: 83-87. 

Marcus, N.H., Lutz, R., Burnett, W., and Cable, P. 1994. Age, viability, and 

vertical distribution of zoplankton resting eggs from an anoxic basin: 

Evidence of an egg bank. Limnology and Oceanography. 39: 154-158. 

Mauchline, J. 1994a. Seasonal variation in some population parameters of 

Euchaeta species (Copepoda: Calanoida). Marine Biology 120: 561-570. 

Mauchline, J. 1994a. Spermatophore transfer in Euchaeta species in a 2000 

m water column. Hydrobiologia 292/293: 309-316. 

McLaren, I.A. 1986. Is "structural" growth of Calanus potentially 

exponential. Limnology and Oceanography 31: 1342-1346. 

Moore, M.V., Folt, C.L. and Stemberger, R.S. 1996. Consequences of 

elevated temperatures for zooplankton assemblages in temperate lakes. Arch 

Hydrobiolgie 3: 289-319. 

Muck, P. and Lampert, W. 1984. An experimental study on the importance 

of food conditions for the relative abundance of calanoid copepods and 

cladocerans. Arch Hydrobiolgie / Supplement 66 2: 157-179. 

Muller-Navarra, D.C., Guss, S. and Storch, H.v. 1997. Interannual variability 

of seasonal succession events in a temperate lake and its relation to 

temperature variability. Global Change Biology 3: 429-438. 

Nishri, A., T. Zohary, M. Gophen, D. Wynne (1998). Lake Kinneret dissolved 

oxygen regime reflects long term changes in ecosystem functioning. 

Biogeochemistry 42: 253 – 283.

Norrbin, M.F. 1994. Seasonal patterns in gonad maturation, sex ratio and 

size in some small, high-latitude copepods: implications for overwintering 

tactics. Journal of Plankton Research. 16: 115-131. 

Osgood, K.E. and Frost, B.W. 1994. Comparative life histories of three 

species of planktonic calanoid copepods in Dabob Bay, Washington. Marine 

Biology 118: 627-636. 

Ostrovsky, I. 1995. The parabolic pattern of animal growth: determination of 

equation parameters and their temperature dependancies. Freshwater 

Biology, 33, 357-371. 

Paffenhofer, G.-A., Bundy, M.H., Lewis, K.D., and Metz, C. 1995. Rates of 

ingestion and their variability between individual calanoid copepods: direct 

observations. Journal of Plankton Research 17: 1573-1585. 

Pagano, M. and Saint-Jean, L. 1994. In situ metabolic budget for the 

calanoid copepod Acartia clausi in a tropical brackish water lagoon (Ebrie 

Lagoon,Ivory Coast). Hydrobiologia 272: 147-161. 

Pasternak, A.F., Arashkevich,E.G. 1999. Resting stages in the life cycles of 

Eudiaptomus graciloides (Lilv) (Copepoda:Calanoida) in Lake Glubokoe. Journal of 

Plankton Research. 21:2, pp309-325. 

Peters, R.H. and Downing, J.A. 1984. Empirical analysis of zooplankton 

filtering and feeding rates. Limnology and Oceanography 29: 763-784. 

Petkovic, S. 1981. Seasonal abundance & distribution of planktonic crustacea. 

The Biota & Limnology of Lake Skadar. Karaman, G.S.; Beeton,A.M. eds. 

Titograd-Yugoslavia, Univerzitet Veljko Vlahovic. Pp.192-199. 

Pinel-Alloul, B., Downing, J.A., Perusse, M., and Codin-Blumer, G. 1988. Spatial 

heterogeneity in freshwater zooplankton: variation with body size, depth, and scale. 

Ecology 69: 1393-1400. 

Ponyi, J.E.,Peter, H.H. Zankai,N.P. 1982. Daily changes in population structure & 

production of Eudiaptomus gracilis during summer in a shallow lake (Balaton,Hungary). 

Journal of Plankton Research.4:4,913-926. 

Ponyi, J.E.,Zankai,N.P. 1982. Population dynamics, biomass and biomass production of 

Eudiaptomus gracilis in two water areas of differing trophic state of Lake Balaton 

(Hungary). Acta Hydrochim. Hydrobiolgia. 10:6, 597-610. 

Por, F.D. 1963. The relict Aquatic Fauna of the Jordan Rift Valley Israel 

Journal of Zoology 12: 47-58. 

Por, F.D. 1966. The living world of Lake Kinneret. Pages 51-55, in: 17th 

Limnological Convention. Jerusalem, Israel.

Por, F.D. 1968a. The benthic copepoda of Lake Tiberias and of some 

inflowing springs Israel Journal of Zoology 17: 31-50. 

Por, F.D. 1968b. The Invertebrate zoobenthos of Lake Tiberias: I. 

Qualitative Aspects. Israel Journal of Zoology 17: 51-79. 

Por, F.D. 1984. An outline of the distribution patterns of the freshwater 

Copepoda of Israel and surroundings. Hydrobiologia 113: 151-154. 

Poulet, S.A., Ianora, A., Miralto, A., and Meijer, L. 1994. Do diatoms arrest 

embryonic development in copepods? Marine Ecology Progress Series 111: 

79-86. 

Pyke, D.A. 1986. Statistical analysis of survival and removal rate 

experiments. Ecology 67: 240-245. 

Radach, G., Carlotti, F. and Spangenberg, A. 1998. Annual weather 

variability and its influence on the population dynamics of Calanus 

finmarchicus. Fisheries Oceanography 7: 272-281. 

Richman, S., Bohon, S.A. and Robbins, S.E. 1980. Grazing Interactions 

among Freshwater Calanoid Copepods. Pages 793, in: Kerfoot, W.C., 

Evolution and Ecology of Zooplankton Communities. 3. University Press of 

New England. Hanover. 

Richman, S. and Dodson, S.I. 1983. The effect of food quality on feeding 

and respiration by Daphnia and Diaptomus. Limnology and Oceanography 

28: 948-956. 

Rigler, F.H. and Cooley, J.M. 1974. The use of field data to derive 

population statistics of multivoltine copepods. Limnology and Oceanography. 

19: 636-655. 

Roman, M.R. and Rublee, P.A. 1980. Containment effects in copepod 

grazing experiments: A plea to end the black box approach. Limnology and 


Santer, B. 1994. Influences of food type and concentration on the 

development of Eudiaptomus gracilis and implications for interactions 

between calanoid and cyclopoid copepods. Arch Hydrobiol. 131: 141-159. 

Santer, B. and Bosch, F.v.d. 1994. Herbivorous nutrition of Cyclops vicinus: 

the effect of a pure algal diet on feeding, development, reproduction and life 

cycle. Journal of Plankton Research 16: 171-195. 

Schnack-Schiel, S.B. and Hagen, W. 1994. Life cycle strategies and seasonal 

variations in distribution and population structure of four dominant calanoid

copepod species in the eastern Weddell Sea, Antarctica. Journal of Plankton 

Research 16: 1543-1506. 

Serruya, C. 1978. Lake Kinneret, Monographiae Biologica. 32. Junk. The 

Hague. p.502. 

Shapiro, J. 1998. Food of the Thin-Lipped Grey Mullet (Liza ramada) in 

Lake Kinneret, Israel. Bamidgeh, Israel. Journal of Aquaculture 50: 3-11. 

Sokal, R., Rohlf, F. J., 1973. Introduction to Biostatistics. W. H. Freeman and 

Co. pp. 368. 

Soto, D. and Hurlbert, S.H. 1991. Long-term experiments on calanoidcyclopoid 

interactions. Hydrobiologia 61: 245-265. 

Soto, D. and Hurlbert, S.H. 1991. Short term experiments on calanoidcyclopoid-phytoplankton 

interactions. Ecology Monographs 215: 83-110. 

Stearns, S.C. 1994. The Evolution of life Histories. Oxford University Press. 

pp.250. 

Stibor, H. 1992. Predator induced life-history shifts in a freshwater 

cladoceran. Oecologia 92: 162-165. 

Stich, H.-B. and Lampert, W. 1981. Predator evasion as an explanation of 

diurnal vertical migration by zooplankton. Nature 293: 396-398. 

Svensson, J.-E. 1992. The influence of visibility and escape ability on sexspecific 

susceptibility to fish predation in Eudiaptomus gracilis (Copepoda, 

Crustacea). Hydrobiologia 234: 143-150. 

Toth, L.G. and Kato, K. 1996. Development of Eodiaptomus japonicus 

Burckhardt (Copepoda,Calanoida) reared on different sized fractions of 

natural plankton. Journal of Plankton Research. 18: 819-834. 

Twombly, S. and Burns, C.W. 1996. Exuvium analysis: A nondestructive 

method of analyzing copepod growth and development. Limnology and 


Uye, S.H. 1988. Temperature-dependant development and growth of 

Calanus sinicus (Copepoda: Calanoida) in the laboratory. Hydrobiologia 

167/167: 285-293. 

Van Duren, L.A. and Videler, J.J. 1995. Swiming behavior of developmental 

stages of the calanoid copepod Temora longicornis at different food 

concentrations. Marine Ecology Progress Series 126: 153-161.

Van Leeuwen, H.C. and Maly, E.J. 1991. Changes in swimming behavior of 

male Diaptomus leptopus (Copepoda: Calanoida) in response to gravid 

females. Limnology and Oceanography 36: 1188-1195. 

Vanderploeg, H.A. 1981. Seasonal particle-size selection by Diaptomus 

sicilis in off-shore Lake Michigan. Canadian Journal of Fish and Aquatic 

Science 38: 504-517. 

Vanderploeg, H.A., Paffenhofer, G.-A. and Liebig, J.R. 1988. Diaptomus vs. 

net phytoplankton: effects of algal size and morphology on selectivity of a 

behaviorally flexible, omnivorous copepod. Bulletin of Marine Science 43: 

377-394. 

Viitasalo, M. 1992. Calanoid resting eggs in the Baltic Sea: implications for 

the population dynamics of Acartia bifilosa (Copepoda). Marine Biology 114: 

397-405. 

Viitasalo, M. and Katajisto, T. 1994. Mesozooplankton resting eggs in the 

Baltic Sea: identification and vertical distribution in laminated and mixed 

sediments. Marine Biology 120: 455-465. 

Viitasalo, M. and Tarja Katajisto, I.V. 1994. Seasonal dynamics of Acartia 

bifilosa and Eurytemora affinis (Copepoda: Calanoida) in relation to abiotic 

factors in the northern Baltic Sea. Hydrobiologia 292/293: 415-422. 

Vuorinen, I., Rajasita, M. and Salo, J. 1983. Selective predation and habitat 

shift in a copepod species-support for the predation hypothesis. Oecologia 

(Berlin) 59: 62-64. 

Watson, N.H.F. 1984. Variability of diapause in copepods. Pages 509-513, 

in: Schriever, G., Schmink, H.K., and Shih, C.-t., Second International 

Conference on Copepoda. 58. National Museum of Natural Science. 

Ottawa, Canada. 

Wetzel, R.G., G.E. Likens (eds), 1991. Limnological Analysis. 3 rd edition. 

Springer Publications, pp.429. 

Williamson, C.E. 1991. Copepoda. Pages 787-809, in: Thorp, J.H. and 

Covich, A.P., Ecology and Classification of North American Freshwater 

Invertebrates. Academic Press, Inc. 

Williamson, C.E., Butler, N.M. and Forcina, L. 1985. Food limitation in 

naupliar and adult Diaptomus pallidus. Limnology and Oceanography 30: 

1283-1290. 

Williamson, C.E., Sanders, R.W., Moeller, R.E., and Stutzman, P.L. 1996. 

Utilization of subsurface food resources for zooplankton reproduction:

Implications for diel vertical migration theory. Limnology and Oceanography 

41: 224-233. 

Williamson, M. 1996. Biological Invasions. Chapman & Hall. London. 

234 p. 

Wilson, D.S. 1973. Food size selection among copepods. Ecology 54: 909- 

914. 

Work, K. and Gophen, M. 1995. The invasion of Daphnia lumholtzi (Sars) 

into Lake Texoma (USA). Arch Hydrobiologia 133: 287-303. 

Yashuv, A. and Alhunis, M. 1961. The dynamics of biological processes in 

Lake Tiberias. Bulletin Research Council of Israel 10B: 12-35. 

Zankai, N.P. 1991. Feeding of nauplius stages of Eudiaptomus gracilis on 

mixed plastic beads. Journal of Plankton Research. 13: 437-453. 

Zaret, T.M. 1976. Vertical migration in zooplankton as a predator avoidance 

mechanism. Limnology and Oceanography 21: 804-813.

Proceedings of the 7 th International Conference on Copepoda 

Curitiba, Brazil 

25-31 July, 1999 

The occurrence of the diaptomid Eudiaptomus drieschi (Poppe and Mrazek 1895) in 

Lake Kinneret, Israel. 

B. Azoulay, M. Gophen, F.D. Por 

Prior to the mid-eighties, diaptomid copepods were not found in the routine samples of 

the pelagic waters of Lake Kinneret. Early surveys reported sporadic appearances of 

diaptomids in the lake, especially after winter floods. After 1986, the consistent presence 

of the diaptomid Eudiaptomus drieschi (Poppe and Mrazek 1895), in the offshore zone 

(pelagic) of Lake Kinneret was recorded. Population densities and life stage distribution 

of copepods have been monitored in the lake since 1996. A strong seasonal periodicity 

was indicated with the highest densities in winter / spring and very low in the summer. 

Two, 24-hour surveys were conducted during those periods. It was observed that during 

the April study (spring) juvenile copepods had a strong association with nanoplankton. 

The high summer temperatures are apparently one of the pressures that drive E. drieschi 

in Lake Kinneret to produce a resting egg. Viable eggs have been extracted from 

sediment cores up to a depth of 10 cm. Experiments examining temperature and salinity 

tolerances were conducted in the lab as well as body length measurements of each life 

stage. Adult E. drieschi do not appear to reproduce in high salinities, and are sensitive to 

high temperatures (>22 0 C).

האאוטאקולוגיה של 

(Poppe and Mrazek 1895) Eudiaptomus drieschi 

‏(קופפודה,‏ קלנואידה)‏ בכנרת.‏ 

חיבור מאת:‏ בוני ר.‏ אזולאי 

מדרכים אקדמאים:‏ 

פרופ.‏ משה גפן 

פרופ.‏ פ.‏ דב פור 

הוגש לסינט האוניברסיטה העברית,‏ ירושלים 

2002 יולי,‏

מ-‏ 

תקציר 

עד אמצע שנות השמונים,‏ דיאפטומידים ‏(קופפודה,‏ קלנואידה)‏ היו רק ‏"אורחים מזדמנים"‏ 

בכנרת.‏ 

במחקרים קודמים דווח על מציאות דלה מפוזרת מאוד בזמן של דיאפטומידים רק באיזור 

הליאוראל של הכנרת,‏ במיוחד לאחר שטפונות חורפיים חזקים.‏ 

בדגימות שנאספו אחרי 1986 

אובחנה נוכחות מתמשכת של אאודיאפטומוס דריישי (Poppe & Mrazek (1895 Eudiaptomus drieschi 

באיזור הפלגיאל של האגם.‏ 

זה הדיווח הראשון ברקורד הזואופלנקטון של הכנרת על תוצאה נרחבת 

של א.‏ דריישי באגם,‏ ודווח ראשון על חדירה כל כך נרחבת שלו אל הכנרת.‏ 

דווחה בעבר מסרי-לנקה,‏ יוגוסלביה,‏ יון ותורכיה.‏ 

מציאותו של א.‏ דריישי 

מעקב רצוף ספירה וחקר אוכלוסיתו החלו 

ב‎1994‎‏-.‏ 

ריכוז האורגניזמים במי האגם,‏ לפי הדרגות במחזור החיים שלו נמדדים בתחנה קבועה 

תחנה F 

‏(עומק 20 מ').‏ 

שבצפון-מערב הכנרת החל משנת 1996. 

לא אובחנו דורות קוהרנטים בתוך אוכלוסיות של א.‏ דריישי בכנרת.‏ 

האוכלוסיות שלו 

בכנרת מראות על הרכב רב-גילי ורבייה רצופה בעונות בהן הוא נפוץ.‏ 

כדי להעריך את הדינמיקה של 

הרבייה שלו נמדדו באופן נסיוני במעבדה הביומסה,‏ קצב גידול וזמן ההתפתחות של כל שלב במחזור 

חייו.‏ פרטים גודלו בטמפרטורות שונות ובדרגות מליחות שונות של מי אגם.‏ 

זמן ההתפתחות של כל 

שלב ותוספת הגידול נמדדו ברציפות.‏ 

מאז 1969 התרחשו במערכת הכנרת מספר שינויים:‏ עלה מגוון המינים של הזואופלנקטון 

באפילימניון של הכנרת ע"י הופעה של מינים חדשים:‏ כידורוס ספריקוס 

(Leydig) (Moina retrorostris) מוינה רקטירוסטריס ; ( By Birge) (Chydorus sphaericus) 

קונוכלילואידס sp.) (Conochiloides ; אנוריאופסיס פייזה fissa) (Gosse)(Anuraeopsis 

אובחנו גם שינויים בפיטופלנקטון ‏(בעיקר ירוקיות,‏ כחוליות ולהוביות),‏ המליחות ירדה מ‎400‎ 

‏"ג 

כלוריד לליטר 

‏(מגכ"ל)‏ בשנות השישים עד ל‎208‎ מגכ"ל בשנות ה‎80‎‏-.‏ 

נמצא שהירידה במליחות היא כנראה הגורם הראשוני לפלישה של א.‏ דריישי לפלגיאל של הכנרת.‏ 

לאחרונה עלתה המליחות שוב עד ל‎283‎‏-‏ מגכ"ל וכיום נעלמו לכן אוכלוסיות ה א.‏ דריישי.‏ 

ריכוזי א.‏ דריישי בכנרת מראים על שינויים עונתיים:‏ ריכוזים גבוהים בחורף-אביב ונמוכים מאוד 

בקיץ-סתיו.‏ 

מיני דיאפטומידים רבים מייצרים שני טיפוסי ביצים:‏ 1) ביצים סוביטאניות כאלו שמתבקעות מיד,‏ 

2) ביצי קיימא-בנטיות שמוטלות,‏ שוקעות לתוך הסדימנטים ומתבקעות מאוחר יותר.‏ 

אוכלוסיות 

א.‏ דריישי בכנרת מתחדשות כל שנה בחורף לאחר ה"היפוך",‏ מתוך ‏"בנק"‏ ביצי קיימא שבסדימנטים

והוטלו שנה קודם לכך בתקופה בה טמפ'‏ המים עלתה אל מעל הטולרס הטרמי שלהם ‏(גבול 

הסבילות הטרמי),‏ שהוא מעל . 22 0 C 

ביצי קיימא שנאספו מהסדימנטים בכנרת אינן שונות באופן 

מורפולוגי מהביצים הסוביטאניות,‏ כפי שנבדק במיקרוסקופ אלקטרוני.‏ 

במיקרוסקופ אור רגיל,‏ 

ולאחר ששומרו ונצבעו בלוגול (1990 (Lohner ניתן להבדיל ביניהן.‏ 

צילומים במיקרוסקופ אלקטרוני 

סורק הראו ששטח הפנים של ביצי קיימא הוא חלק,‏ וללא קוצים או סטרקטורות בולטות אחרות.‏ 

עובדה זו מרמזת על אפשרות שתפוצתן יכולה להעשות ע"י דגים.‏ 

נמצאו ביצי קיימא במערכת 

העיכול של דגיגי שפמנון בכנרת.‏ 

יתכן ש א.‏ דריישי הגיע לכנרת ע"י צפרים נודדות טורפות דגים 

והופץ באגם ע"י דגים בנטיבוריים.‏ 

פלישה של אורגניזמים אקוסטיים לתוך אקוסיסטמה שלא היו בה מקודם היא מדד לשינויים 

שעוברת המערכת ‏(הרבה פעמים מעשה ידי-אדם)‏ המאפשרים לאורגניזם הפולש להתבסס בה.‏ 

אורגניזם פולש מוגדר ככזה לאחר שנצפתה תפוצה שלו שונה מתחום התפשטותו בעבר.‏ 

הצלחת 

הפלישה היא בד"כ מועטה.‏ א.‏ דריישי הצליח לפלוש לאפילימניון של הכנרת ע"י כך שתפש חלקית 

מקומם של אחרים בתוך נישה אקולוגית זו שהיתה תפוסה כולה בעבר והסתגל לטמפרטורות 

הקיצוניות ע"י יצירת ביצי קיימא.‏

עבודה זו נעשתה בהדרכתם של:‏ 

פרופ.‏ פ.‏ דב פור,‏ 

מחלקת אבולוציה ‏,ססטמטיקה,‏ ואקולוגיה 

האוניברסיטה העברית,‏ ירושלים.‏ 

פרופ.‏ משה גפן,‏ 

המעבדה לחקר הכנרת ע'ש יגאל אלון,‏ 

חקר ימים ואגמים לישראל,‏ בע'מ.‏

האאוטאקולוגיה של (Poppe and Mrazek 1895) Eudiaptomus drieschi 

‏(קופפודה,‏ קלנואידה)‏ בכנרת.‏ 

חיבור לשם קבלת התואר ‏"דוקטור לפילוסופיה"‏ 

מאת בוני רשל אזולאי 

הוגש לסינט האוניברסיטה העברית,‏ ירושלים 

2002 יוני

The Autecology of Eudiaptomus cf drieschi (Poppe & Mrazek 1895 ...

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