Abstract

Introduction

From the fourteen species of Annitella recorded from Europe, seven are restricted to the Pyrenees and the Iberian Peninsula (Annitella amelia Sipahiler, 1998; A. cabeza Sipahiler, 1998; A. esparraguera Schmid, 1952; A. iglesiasi González & Malicky, 1988; A. lalomba Sipahiler, 1998; A. pyrenaea Navas, 1930; and A. sanabriensis Gonzalez & Otero, 1985). The remaining species are either restricted to European ecoregion 10 (Carpathians; A. chomiacensis Dziedzielewicz, 1908; A. lateroproducta Botoşăneanu, 1952), ecoregion 5 (Dinaric Western Balkan; A. apfelbecki (Klapálek, 1899); A. singularis Klapálek, 1902) or cover a wider range (A. obscurata McLachlan, 1876; A. thuringica Ulmer, 1909; A. triloba Marinkovic, 1955) (Euro-limpacs Consortium 2007, Malicky 2004). A. dziedzielewiczi Schmid, 1952; A. kosciuszkii Klapálek, 1907 and A. transsylvanica Murgoci, 1957 seem to be transitional taxa between A. chomiacensis and A. lateroproducta (Szczesny 1979, Malicky 2005) and were therefore omitted in the species inventory by Malicky (2004).

In the genus Melampophylax, three of the six European species are restricted to only one ecoregion (M. austriacus Malicky, 1990: Alps; M. polonicus Malicky, 1990: Carpathians; M. vestinorum Moretti, 1991: Italy); the distributional area of the remaining three species (M. melampus McLachlan, 1876; M. mucoreus Hagen, 1861; M. nepos McLachlan, 1880) covers wider ranges (Euro-limpacs Consortium 2008, Malicky 2004).

From all these European Annitella and Melampophylax species, only the larvae of A. obscurata (Lepneva 1966, Waringer & Graf 1997), A. thuringica (Bolzhuber 1998, Waringer & Graf 2004), M. mucoreus (Higler 2005, Tachet et. al. 2000, Vieira-Lanero 2000, Wallace et al. 2003, Waringer & Graf 1997) and M. melampus (Waringer 1987, Waringer & Graf 1997) are known. Recently, however, larvae of an unknown Annitella species, morphologically very close to genus Melampophylax, were collected by W.G., M.K., A.P. and I.V. in the river Cetina, Croatia. The larvae could be clearly associated with A. apfelbecki by rearing them to adults in the lab. This material enabled us to describe this hitherto unknown species. In addition, Ottó Kiss (Hungary) kindly provided some larvae of Melampophylax nepos described by him (Kiss 1978) which were very helpful for providing some additional morphological information and for evaluating morphological characters for the differentiation of the two species.

Description of the fifth instar larvae of Annitella apfelbecki and Melampophylax nepos

Material examined

A. apfelbecki: 68 fifth, 15 fourth, 11 third and 2 second instar larvae from the spring of Cetina River, Croatia (43° 58′ 36,1″ N, 16° 25′ 48,6″ E, altitude 386 m a.s.l.), leg. I. Vučković, M. Kučinić and A. Previšić on many occasions throughout 2004, 2005 and 2007. M. nepos: 3 fifth and 1 fourth instar larvae from Sebesviz Stream, Bükk Mountains, Hungary, leg. Otto Kis on 14 May, 2000. M. mucoreus: 2 fifth instar larvae from the Fulda River, Germany, leg. T. Pitsch on 24 May, 1981.

Both species are morphologically very similar to each other. The body length of final instar larvae ranges from 10.0 to 12.4 mm (fourth instar: 7.0 - 8.2 mm) in A. apfelbecki and from 11.7 to 12.6 mm (fourth instar: 10.2 mm) in M. nepos. The head width, in the same sequence of species, ranges from 1.15 to 1.61 (fourth instar: 0.93 – 1.02 mm; other instars: Figs. 12, ​,13)13) and from 1.31 to 1.33 mm (fourth instar: 1.04 mm). Larval case length ranges from 10.7 to 14.5 mm (fourth instar: 8.0 -- 8.5 mm) and 13.0 to 16.3 mm (fourth instar: 12.5), anterior case width from 3.7 to 4.0 mm (fourth instar: 3.0 -- 3.6 mm) and 3.0 to 3.5 mm (fourth instar: 3.1 mm); posterior case width ranges from 3.5 to 4.2 mm (fourth instar: 2.8 – 3.1 mm) and 2.8 to 3.0 mm (fourth instar: 3.2 mm). The cases of both species are slightly curved, slightly tapering at the posterior end and consist completely of mineral particles with grain sizes insignificantly increasing in anterior direction (Figs. 10, 11).

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Figures 1-11

(1-2) Head capsule, frontal view of (1) Annitella apfelbecki; (2) Melampophylax nepos; (3) A. apfelbecki, fifth instar larva, head and prothorax, right lateral view; white arrow: prosternal horn, black arrow: transverse rim; (4) first abdominal sternum, ventral view of (a) A. apfelbecki, (b) M. nepos, (5) thorax and first abdominal tergum of A. apfelbecki, dorsal view; am: antero-median sclerites, pm: postero-median sclerites, l: lateral sclerites, arrows: lateral and dorsal protuberance on first abdominal segment; (6) right hind legs of fifth instar larvae, posterior view, (a) Melampophylax nepos, (b) Melampophylax mucoreus; arrows: tarsi; (7) A. apfelbecki, fifth instar larva, metathorax and abdominal segments 1—3, left lateral view; arrow: posterior sclerite on lateral protuberance; (8-10) A. apfelbecki, fifth instar larva, (8) tip of abdomen, left lateral view; (9) tip of abdomen, dorsal view; (a) row of posterodorsal setae on segment 8; arrows: row of posterodorsal setae on segment 7; (10) case, right lateral view; (11) cases of fifth instar larvae of (a) M. nepos, (b) M. mucoreus. Scale bars: 1000μm.

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Figure 12

Frequency distribution histogram of measurements of maximum head widths of 79 larvae of Annitella apfelbecki. Instar numbers are indicated at top.

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Figure 13

Relationship between the logarithmus naturalis of head width (mm) and instar number (each full dot is the geometric mean with S.D.) of A. apfelbecki. The broken line superimposed on the data is the regression line with its equation shown in the diagram. Empty dot: extrapolations from the regression equation for instar 1. Data on mean head widths for the instars are given at the side of each dot.

Head capsules and all body sclerites are dark brown to black brown in A. apfelbecki and medium brown to yellowish brown in M. nepos. Tiny head spinules cover most of the dorsal surface of the parietalia and the frontoclypeus (Figs. 1, 2). The mandibles lack terminal teeth along edges as well as ridges in the central concavity of both species (Fig. 1, arrow). Such a spoon-shaped mandible – also known from most European Drusinae species – identifies them as scrapers that mainly feed on epilithic or aufwuchs algae.

Pronotum with transverse rim at the anterior third like in all Limnephilinae (Fig. 3, black arrow). The pronotal surface of both species is covered by dark brown setae of unequal length: the longest ones are situated at the anterior border and in the central area (Fig. 3). The pentagonal prosternites are conspicuous and brown in colour; a prosternal horn is present in both species (Fig. 3, white arrow). The mesonotum is completely covered by two yellowish brown to black brown sclerites (Fig. 5). The metanotum is partially covered by three pairs of sclerites with the anterior metanotal sclerites being large and oval; their median separation is distinctly smaller than their maximum extension along the body axis in both species (Fig. 5 am). Faces of mid- and hind femora lack additional setae (Fig. 6).

First abdominal segment with fleshy protuberances in dorsal and lateral positions (Fig. 5, arrows). Posterior region of first abdominal lateral protuberances with a large sclerite without setae, but with 1 or 2 holes (Fig. 7, arrow). A small group of setae is present between the both posteromedian sclerites (Fig. 5). The setal bases at the central section of the first abdominal sternum show a marked tendency of fusing in M. nepos (Fig. 4b). This is not the case in A. apfelbecki (Fig. 4a) where only occasionally two setal bases touch each other. At the seventh abdominal dorsum, A. apfelbecki has 4 posterodorsal setae (Fig. 9, arrows), whereas only two are present in M. nepos. The eighth abdominal segment bears thirteen to fourteen posterodorsal setae in A. apfelbecki and eleven to fourteen in M. nepos (Fig. 9a).

All gills consist of single filaments only. Dorsal gills are present from the second (presegmental position) to the fifth (postsegmental position) and ventral gills from the second (presegmental) to the seventh segment (presegmental) in both species. Dorsolateral gills are present from the second (presegmental) to the fourth (presegmental position) in A. apfelbecki and at the third segment (presegmental) only or completely lacking in M. nepos. Ventrolateral gills range from the second segment (postsegmental) to the third or fourth segment (postsegmental) in both species. The lateral fringe is present from the last third of the second or the beginning of the third (Fig. 7) to the end of the eighth abdominal segment (Fig. 8).

Morphological separation of Annitella apfelbecki and Melampophylax nepos from other European Trichoptera

A summary of morphological features for the identification of limnephilid larvae is given in Waringer (1985). Within the framework of the limnephilid key by Waringer & Graf (1997, 2004), Annitella apfelbecki and Melampophylax nepos are separated from other species by the following features:

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  Gills present, consisting of single filaments only (Fig. 7);

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  Metanotum covered by three pairs of small sclerites (Fig. 5 am, pm, l);

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  Head and pronotum without a thick layer of woolly hairs (Figs. 1 - 3);

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  Head capsule without groups of additional spines, without central concavity and rims surrounding the frontoclypeus (Figs. 1 - 3);

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  First abdominal sternum without a large median sclerotized patch (Fig. 4);

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  Pronotum with transverse rim at the anterior third (Fig. 3, black arrow) and without depressions, a dorsal hump or ridges (Fig. 3);

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  Mandibles lacking terminal teeth along edges as well as ridges in the central concavity (Fig. 1, arrow);

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  Faces of mid- and hind femora without additional setae (Fig. 6).At this point, A. apfelbecki and M. nepos are keyed out together with Melampophylax mucoreus (Hagen, 1861) which has been also figured and/or included in the keys by Higler (2005), Tachet et. al. (2000), Vieira-Lanero (2000) and Wallace et al. (2003). A summary of morphological and distributional data for the separation of the three species is given in Table 1.

  Table 1

  Synoptic key for the identification of fifth instar larvae of Annitella apfelbecki, Melampophylax mucoreus and M. nepos. Countries with more than one species of this group are indicated with bold letters.

  Species/character	Hind tarsal length (mm; Fig. 6, arrows)	Posterodorsal setae, 8th segment	Posterodorsal setae, 7th segment	Setal bases at first abdominal sternum	Distribution
  A. apfelbecki	0.73 -- 0.74	13 -- 14	4	almost never fused	Bosnia & Herzegovina, Croatia, Kosovo, Montenegro, Serbia, Voivodina
  M. mucoreus	0.77 -- 0.80	9 -- 10	2	almost never fused	Austria, Belgium, Great Britain, France, Germany, Luxembourg, Romania, Spain, Switzerland, The Netherlands
  M. nepos	0.51 -- 0.59	11 -- 14	2	many fused	Austria, Czech Republic, Germany, Hungary, Poland, Romania, Slovakia

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A. apfelbecki is restricted to ecoregion 5 (Dinaric Western Balkan; Euro-limpacs Consortium, 2007) from where the other two species are not recorded. It has 4 posterodorsal setae on abdominal segment 7 (Fig. 9, arrows), whereas only two are present in M. nepos and M. mucoreus. There are also differences in the number of posterodorsal setae on the eighth abdominal segment (Fig. 9a), but there is an overlap in A. apfelbecki and M. nepos (Table 1). In addition, leg lengths vary greatly in the three species (Fig. 6): the longest legs are present in M. mucoreus (hind tarsus length of fifth instar larvae: 0.77 - 0.80 mm) whereas in M. nepos the legs are significantly shorter (hind tarsus length: 0.51 - 0.59 mm; Fig. 6); A. apfelbecki takes an intermediate position (0.73 – 0.74 mm). Finally, the sclerotized setal bases of the first abdominal sternum have a marked tendency of fusing in M. nepos (Fig. 4b), whereas this is only the case in single sclerites in M. mucoreus and A. apfelbecki (Fig. 4a).

Phenology, habitat, feeding ecology and distribution

The geographical range of Annitella apfelbecki comprises European ecoregion 5, i.e. the Dinaric Western Balkan (Euro-limpacs Consortium 2007) where the species is known from Bosnia & Herzegovina, Croatia and the part of former Yugoslavia which now forms the territories of Kosovo, Montenegro, Serbia, and Voivodina (Barnard 2007). A. apfelbecki is restricted to spring areas; our material is from the spring of River Cetina in Croatia where in May 2005 the proportion of A. apfelbecki with respect to the total number of caddisfly species was up to 83%. At this location seventeen other taxa of Trichoptera were observed: Rhyacophila balcanica Radovanovic, 1953; R. fasciata Hagen, 1859; Glossosoma discophorum Klapálek, 1902; Hydropsyche sp., Chaetopteryx fusca Brauer, 1857; Ecclisopteryx dalecarlica Kolenati, 1848; Grammotaulius nigropunctatus (Retzius, 1783), Limnephilus flavicornis (Fabricius, 1787), L. lunatus Curtis, 1834; L. vittatus (Fabricius, 1798), Micropterna nycterobia McLachlan, 1875; M. testacea (Gmelin, 1789), Stenophylax permistus McLachlan, 1895; Allogamus uncatus (Brauer, 1857), Halesus digitatus (Schrank, 1781); Sericostoma flavicorne Scheider, 1845 and Odontocerum albicorne (Scopoli, 1763). Apart from the Cetina spring we found A. apfelbecki in the spring of Zeleni Vir, in the spring of the Kupa River in the Gorski kotar region, the western part of Croatia, the most western point in the area of A. apfelbecki, and in the springs of the Sturba Rivers in Bosnia and Herzegovina. At these locations, larvae of A. apfelbecki were collected at a water depth up to 60 cm, at current velocities up to 17.3 cms⁻¹ and on different types of substrate, especially on macrophytes. Monthly measurements of physico-chemical parameters during 2004 and 2005 showed the following values for Cetina spring: Alkalinity: 155 to 185 mgCaCO₃/l, conductivity: 285 to 356 μS/cm, pH: 7.49 to 7.77, oxygen saturation: 94 to 148%, dissolved oxygen: 10.4 to 15.0 mgl⁻¹ and water temperature: 8.4 to 12.9 °C. At our sites, larvae could be collected throughout the year except from October to December. A frequency distribution histogram of head widths of the larvae (Fig. 12) clearly separates the larvae into instars 2 to 5 with the fourth instar being defined as ≤ 1.05 mm. Dyar’s rule was well applicable for head widths of A. apfelbecki, enabling the extrapolation of head widths for first instars (Fig.13)). Additionally, second and third instars were present at the Cetina site in January, which most probably were the offspring from adults emerging early in the flight period (October and November). One late fifth instar was also collected in January, probably prior to pupation and emerging in late January. Fifth instar larvae were collected as early as March, which became the dominant instar from May to September (Fig. 14). In Cetina, A. apfelbecki is on the wing from October to January.

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Figure 14

Life history diagram of A. apfelbecki, showing the percentage of larval instars 2 to 5 in monthly intervals. The diagram is based on a total of 77 specimens.

Based on adult morphology, Melampophylax nepos is split into two subspecies, the nominate subspecies and M. nepos triangulifera Botoşăneanu whereas M. nepos nepos is present in European ecoregions 9 and 10 (Central Highlands and Carpathians; Euro-limpacs Consortium, 2007). Subspecies triangulifera is restricted to the Carpathians. M. nepos is known from Upper Austria, the Czech Republic, Germany, Hungary, Poland, Romania, and Slovakia (Barnard 2007, Malicky 1999). Our material was collected in Sebesviz Stream, located in the Bükk Mountains in northeastern Hungary. M. nepos has been attributed to caddisfly community “S” by Szczesny (1986); this community, indicated by a dominance of Allogamus starmachi Szczesny 1967 and M. nepos, is situated well above 1000 m in the Tatra streams and seems to be typical for streams that dry up in autumn and winter. In the Waksmundzki Potok brook in the High Tatras, first instar larvae were observed at the end of April, second instars at the end of May, third and fourth instars in June and July, final instar larvae in July and August, and pupae were collected from August to October (Szczesny 1986). According to Tobias & Tobias (1981), M. nepos is on the wing in September.

As in Drusinae, there seems to be an evolutionary progression in genus Annitella and Melampophylax from omnivorous shredders (e.g. A. obscurata, A. thuringica, M. melampus) to epilithic grazers (e.g. A. apfelbecki, M. mucoreus, M. nepos). Mandibles with teeth appear to be the ancestral state; the spoon-shaped grazer mandible seems to be derived, having reduced or lost the teeth on the mandible edge (Pauls et al. 2008).

Acknowledgements

References