Two New Marine Gastrotrichs of the Genus Ptychostomella (Macrodasyida,
Thaumastodermatidae) from South Korea
Author(s): Ji Min Lee and Cheon Young Chang
Source: Zoological Science, 20(4):481-489. 2003.
Published By: Zoological Society of Japan
DOI: http://dx.doi.org/10.2108/zsj.20.481
URL: http://www.bioone.org/doi/full/10.2108/zsj.20.481
BioOne (www.bioone.org) is a nonprofit, online aggregation of core research in the biological, ecological,
and environmental sciences. BioOne provides a sustainable online platform for over 170 journals and books
published by nonprofit societies, associations, museums, institutions, and presses.
Your use of this PDF, the BioOne Web site, and all posted and associated content indicates your acceptance of
BioOne’s Terms of Use, available at www.bioone.org/page/terms_of_use.
Usage of BioOne content is strictly limited to personal, educational, and non-commercial use. Commercial
inquiries or rights and permissions requests should be directed to the individual publisher as copyright holder.
BioOne sees sustainable scholarly publishing as an inherently collaborative enterprise connecting authors, nonprofit publishers, academic institutions,
research libraries, and research funders in the common goal of maximizing access to critical research.
2003 Zoological Society of Japan
ZOOLOGICAL SCIENCE 20: 481– 489 (2003)
Two New Marine Gastrotrichs of the Genus Ptychostomella
(Macrodasyida, Thaumastodermatidae) from South Korea
Ji Min Lee and Cheon Young Chang*
Department of Biology, College of Natural Sciences, Daegu University,
Gyeongsan, 712-714 Korea
ABSTRACT—Two new thaumastodermatid gastrotrichs belonging to the genus Ptychostomella are
described from the shallow sublittoral sand bottom in the eastern coast of South Korea. In having the
embossed cuticular armature, Ptychostomella orientalis n. sp. is most allied to P. lepidota Clausen, 2000,
the only congeneric species so far known as possessing such a cuticular armature. Ptychostomella papillata n. sp. is characterized by the terrace-shaped cuticular protrusion on head region, and the numerous
papillae with sensory hair(s). Description of the two new species is prepared with a character comparison
table and a key to the species of Ptychostomella. This is the first record of genus Ptychostomella from the
North Pacific.
Key words: taxonomy, meiofauna, Gastrotricha, Ptychostomella, Korea
INTRODUCTION
Genus Ptychostomella belongs to the family Thaumstodermatidae which is a representative taxon constituting the
most diversified natural group of marine gastrotrichs (Chang
et al., 1998a). Thaumastodermatid gastrotrichs usually have
evolved the various cuticular armature such as sculptured
plates, spines, or combinations of both. However, it had
been supposed that Ptychostomella gastrotrichs had lost the
cuticular sculpture (Ruppert, 1988), before Clausen (2000)
described P. lepidota from the Tromsø region, Norway,
which was armed with “scale-like cuticular elevations”. The
genus Ptychostomella is still poorly known, and only seven
species have been recognized so far since it was established by Remane (1926) on the basis of P. pectinata from
the North Sea (Kiel, Germany).
So far twelve thaumastodermatid species of four genera have been recorded in the Northwest Pacific, including
four species from Japan: Tetranchyroderma dendricum
Saito, 1937 from Hiroshima (Saito, 1937), T. schizocirratum
Chang, Kubota and Shirayama, 2002, Thaumastoderma
clandestinum Chang, Kubota and Shirayama, 2002, and
Platydasys itoi Chang, Kubota and Shirayama, 2002 from
Nanki-Shirahama, southwest Honshu (Chang et al., 2002),
and eight species from South Korea: Th. copiophorum
Chang, Lee and Clausen, 1998, T. gracilium Chang, Lee
and Clausen, 1998, Th. coronarium Chang, Lee and
* Corresponding author: Tel. +82-53-8506454;
FAX. +82-53-8506459.
E-mail: cychang@daegu.ac.kr
Clausen, 1998, Th. appendiculatum Chang, Lee and
Clausen, 1998, T. heterotentaculatum Chang and Lee,
2001, T. hoonsooi Chang and Lee, 2001, Pseudostomella
longifurca Lee and Chang, 2002, and P. koreana Lee and
Chang, 2002 (Chang et al., 1998a, b; Chang and Lee, 2001;
Lee and Chang, 2002). However, the report on Ptychostomella is still lacking from this area.
This paper deals with the description of two new Ptychostomella species, P. orientalis and P. papillata, from
South Korea. The intraspecific variability of the new species
and the affinities with seven congeners are discussed. We
also provide a key to the species of the genus.
MATERIALS AND METHODS
Materials were collected from the shallow sublittoral sand bottom at five rocky shores of Sokcho, Yangyang, Uljin, Ganggu and
Namho in the East Sea of Korea (Sea of Japan, Fig. 1).
Samplings were made by scooping the top sediment into polyethylene vinyl bag or 700 ml volume plastic bottles by SCUBA or
skin diving. In the laboratory the gastrotrichs were extracted by the
anesthetization-decantation technique using 7% MgCl 2 (Ruppert,
1988), and fixed in 5% buffered formalin.
Specimens were mounted in glycerin on H-S slide (Shirayama
et al., 1993) after treatment in a solution of 5% glycerin –95% ethyl
alcohol for 1–2 days, and observed and photographed using a differential interference contrast microscope (Olympus BX-50)
equipped with Nomarski optics. All drawings and measurements
were made with the aid of a camera lucida. Minute morphological
characters like sensory hairs and inner genital organs were examined and video-recorded in living worms using a CCD camera
(Olympus DP-11).
The SEM material was prefixed for 4–6 hr at 4 °C with 2.5% glu-
482
J. M. Lee and C. Y. Chang
Fig. 1. A map showing the localities. 1, Sokcho; 2, Hajodae,
Yangyang; 3, Uljin; 4, Ganggu; 5, Namho, Youngdeok. (Symbol as
follows: ▲ Ptychostomella orientalis, ● P. papillata)
taraldehyde in 0.1M phosphate buffer (pH 7.4), then followed by
postfixation with 2% cold osmium tetroxide in the same buffer for
1.5–2 hr. After dehydration through a graded series of ethanol (50–
100% at 10% intervals) for 30 min each, the material was critical
point dried, coated with lead and platinum-palladium in a high evaporator, and then examined in a Hitachi S-4300 scanning electron
microscope operated at 15KV.
Terminology mostly follows Ruppert (1991) and Clausen
(2000). Abbreviations used in text and table are as follows: Lt = total
length, from anterior tip of head to posterior tip of pedicles including
adhesive tubes; U = percentage unit of Lt, used for the location (U-)
from anterior to posterior, or for the relative length (-U); PhJIn =
junction between pharynx and intestine; TbA = anterior adhesive
tubes; TbL = lateral adhesive tubes; TbP = posterior adhesive
tubes; TbV = ventral adhesive tubes; TbVL = ventrolateral adhesive
tubes.
DESCRIPTION
Family Thaumastodermatidae Remane, 1926
Genus Ptychostomella Remane, 1926
Ptychostomella orientalis new species
(Figs. 2– 4)
Material examined: Nine individuals, Yangjeong, Uljin
(37°00'57''N, 129°24'52''E), 10 May 2001, C. Y. Chang, J. M.
Lee and Y. H. Song. Holotype (DG0701) and six paratypes
(DG0702~0707) are kept in the author’s collection at the
specimen room of the Department of Biology, Daegu University. Another two paratypes, mounted in glycerin on H-S
slide, are deposited in the U.S. Natural Museum of Natural
History, Smithsonian Institution (USNM1008311) and the
Natural History Museum, Ewha Womans University, Seoul
(EWNHM60271).
Additional material examined: Four individuals,
Bongpo, Sokcho (38°14'57''N, 128°34'08''E), 25 Aug. 1996,
H. S. Rho; 1 individual, Hajodae, Yangyang (38°01'16''N,
128°43'38''E), 11 Jun. 1998, J. M. Lee and C. Y. Chang; 11
individuals, Namho, Youngdeok (36°19'38''N, 129°22'54''E),
23 Jun. 2001, J. M. Lee and Y. H. Song.
Diagnosis: Ptychostomella with small body; with a
short, bilobed caudum; lacking eyespot; bearing paired
knob-like tentacles; dorsal surface embossed with smooth
hemispherical cuticular elevations; adhesive tubes: 3 TbA
per side; 1 stumpy TbVL a little behind TbA; TbV with 1 +
2(3) + 1 + 1 + 2 arrangement per side in intestinal region,
of which second and fifth ones forming feet; 2 TbL per side,
first one just behind mid-trunk and second at lateroposterior
edge of body; bilobed caudum furnished with 7–8 TbP per
side, each forming a pedicle; pedicle with 2 distal, 2 lateral
and 3–4 medial tubes; copulatory organ oblong.
Description of the holotype: Body relatively minute
and vase-shaped, Lt 246 µm long; pharynx 66 µm long,
measured from the lower lip of the mouth opening, with
paired pharyngeal pores opening at U35; lateral sides of
body weakly constricted at neck region and a little swollen
at trunk region. Widths of oral opening/neck/PhJIn/trunk/
caudal base 45/37/43/54/26 µm at U07/U21/U38/U57/U94,
respectively.
Oral hood slightly protruding anteriorly with gently undulating border. Sensory hairs situated along anterior margin
of oral hood, ranging 6–13 µm long; 4 pairs of hairs
implanted on anterodorsal surface of oral hood consisting of
2 submesial pairs and 2 lateral ones; more than 10 minute
hairs lined ventrally in a row behind the oral opening at U11;
several pairs scattered on lateral or dorsolateral side from
neck to trunk region (U12-U95). Eyespot lacking. Paired
knob-like tentacles protruding dorsolaterally, just behind
posterolateral corner of head (U09), each furnished with 1
short sensory bristle and 1–2 hairs. Numerous epidermal
glands irregularly situated at subdorsal and subventral
surface along nearly whole body length (U09-U94), with
generally circular shape, mixed in size (from 2 to 8 µm in
diameter).
Cuticular armature embossed with small (2–3 µm in
diameter) and smooth hemispherical tubercles on dorsal
and lateral surfaces as in Fig. 3B.
Ventral cilia covering the entire mid-ventral surface,
from just behind the anterior adhesive tubes to the base of
caudum.
Adhesive tubes: TbA 3 per side, ca. 7–10 µm long, distributed in a nearly horizontal row behind oral opening at
U14, composed of 1 medial tube and 2 lateral ones a little
apart from medial one; 1 TbVL rather short and stumpy, 7
µm long, situated a little behind TbA at U18; TbV 7–8 per
side more or less evenly spaced in intestinal region (from
Ptychostomella Gastrotrichs from Korea
Fig. 2.
Ptychostomella orientalis new species. A, habitus, dorsal; B, habitus, ventral. Scale bar=30 µm.
483
484
J. M. Lee and C. Y. Chang
Fig. 3. Ptychostomella orientalis new species. A, habitus, ventral;
B, dorsal surface embossed with smooth hemispheres. SEM micrographs. Scale bars: A=30 µm; B=3 µm.
U42 to U79), somewhat slender and ranged ca. 10–13 µm
long, with 1 + 2(3) + 1 + 1 + 2 arrangement (at U42/U54/
U62/U71/U79), of which second and fifth ones forming feet;
2 TbL per side, first one 7 µm long, rather ventrolaterally
(U67), and second 9 µm long, quite robust, located at lateroposterior edge of body (U91); a short bilobed caudum each
forming a pedicle, furnished with 7–8 TbP, comprising 2
distal (8 µm long), 2 lateral (5 µm) and 3–4 medial tubes (6
µm).
Reproductive apparatus: Testis single on right side, its
tip at U43 not reaching PhJIn; vas deferens apparently not
coiled, and inner wall shown as a little thickened at its posterior portion (U80-U86). Copulatory organ large, elongate
and rather oblong (22 µm X 42 µm, 9U X 18U), located at
U73-U91, surrounded spirally with thin muscles. Seminal
receptacle oval (8 µm X 10µm), just in front of copulatory
organ, containing spermatozoa. Spermatozoa filiform. Two
suboval eggs with different sizes (ca. 24 µm X 61 µm and
10 µm X 18 µm, respectively) situated dorsally in mid-intestinal region, maturing anteriorly.
Specimens occurred in the subtidal medium sands
along the middle coast of the East Sea (the Sea of Japan).
Measurements and variability: Body lengths of ten
adult type specimens ranged from 223 µm to 262 µm (mean
240 µm, standard deviation 10), maximum widths 46–69 µm
(19U-26U), when mounted in glycerin.
The arrangement and number of adhesive tubes
showed some variability according to individuals. TbA
showed a relatively consistent arrangement as 3 pairs in a
horizontal row, except for only one of 24 specimens examined, which possessed an additional tube. As shown in Fig.
4, the arrangement and number of TbV were much variable
and often asymmetrical, however, second and last TbV
unexceptionally formed the feet. Pedicles were equipped
with 2 distal TbP in all adults examined, while the arrangement of lateral or medial TbP were variable, ranging 1-2 and
2-4 tubes per side respectively, sometimes with the asymmetrical array.
Pre-mature individuals not found among the specimens
examined.
Etymology: The specific name orientalis alludes to the
type locality of this new species, the first record of genus
Ptychostomella in the East Asia.
Remarks: Seven species are currently recognized in
the genus Ptychostomella Remane, 1926: P. pectinata
Remane, 1926, P. ommatophora Remane, 1927, P. mediterranea Remane, 1927, P. helana Roszczak, 1939, P. tyrrhenica Hummon, Todaro and Tongiorgi, 1993, P. bergensis
Clausen, 1996, and P. lepidota Clausen, 2000.
As already mentioned, Ptychostomella had been known
as the unusual thaumastodermatid genus with the smooth
cuticule. Recently, Clausen (2000) described P. lepidota
from the Tromsø region, Norway, which was armed with a
sculptured cuticular structure of “circular, convex and
smooth, scale-like cuticular elevations”. In having the
embossed cuticular armature of hemispherical elevations,
much similar to those of P. lepidota, the new species is supposedly most related to it. Moreover, both species share two
pairs of TbL and the absence of eyespot. However, P. orientalis is discernible from P. lepidota in having three pairs
of TbA, paired knob-like tentacles, and an oblong copulatory
organ.
Ptychostomella Gastrotrichs from Korea
Fig. 4.
485
Ptychostomella orientalis, variations in the number and arrangement of ventral adhesive tubes. Scale bar=30 µm.
Beside the presence of the cuticular armature, P. orientalis is clearly distinguished from the other congeners by the
character combination, as shown in Table 1: (1) bearing the
paired knob-like cephalic tentacles; (2) lacking eyespot; (3)
the arrangement of adhesive tubes, especially, number of
TbA, presence of ventral foot (TbV), number and location of
TbL, and arrangement of TbP; (4) shape of copulatory
organ.
Ptychostomella papillata new species
(Figs. 5, 6)
Material examined: Fourteen individuals (1 juvenile),
Ganggu, Youngdeok (36°22'38''N, 129°24'40''E), 17 Oct.
2000, J. W. Choi and Y. H. Song. Holotype (DG0801) and
11 paratypes (DG0802~0812) are kept in the authors’ collection at the specimen room of the Department of Biology,
Daegu University. Another two paratypes, mounted in glycerin on H-S slide, are deposited in the U.S. Natural Museum
of Natural History, Smithsonian Institution (USNM1008312)
and the Natural History Museum, Ewha Womans University,
Seoul (EWNHM60272).
Diagnosis: Ptychostomella with scalloped anterior border and short, bilobed caudum; terrace-shaped cuticular
protrusion with papillae on head region; 7 small papillae on
each subdorsal surface; 13 dorsolateral groups of papillae
along each side, each group composed of 2–3 papillae; 12
ventrolateral subconical papillae per side, each with a long
sensory hair; adhesive tubes: 5–6 TbA per side forming an
arc; 20 TbVL and 3 TbL per side; caudum with pedicles
poorly developed, each bearing 2 distal, 1 medial and 5–7
lateral TbP; copulatory organ weakly pyriform; vas deferens
coiled or folded at its middle.
Description of the holotype: Body relatively short, 234
µm long; pharynx length 80 µm long; pharyngeal pores
basal, but extend forward to exit at U36. Body sides more
and less parallel in pharyngeal region, weakly swollen in
trunk region, then a little narrowing to a short bilobed caudum. Widths of oral opening/neck/PhJIn/trunk/caudal base
40/39/53/58/37 µm at U06/U26/U45/U66/U93 respectively.
Oral hood a little protruding with scalloped border; anterior edge furnished with 12–13 papillae each bearing 2–3
sensory hairs on its tip. A terrace-shaped cuticular protrusion (Figs. 5A, 6B) prominent on anterodorsal surface of
head, bilaterally forming arcs (U04-U10), each with 5 papillae; medialmost papilla notably bigger, with 3 sensory hairs,
pointing outward; second one with only 1 sensory hair,
rather slenderer than others, close to the former; outer 3
papillae each with 1–3 sensory hairs, along anterior rim of
the terrace. A pair of transverse ridges situated slightly
behind the terrace (U07); one small papilla with 1 short sensory hair situated on the ridge.
Dorsal surface somewhat swollen, and ornamented
with 7 small papillae located subdorsally at U20-U80 in 2
columns; one small papilla locating just ahead of posterior
edge of trunk (U95). Dorsolateral sides aligned by 13 groups
of papillae, comprising 5 pairs in pharyngeal region (from
U12 to U40) and 8 pairs in trunk region (from U47 to U98);
first group made of single papilla, second and fourth of 3
papillae each, and others of 2 papillae (one of which bears
a long hair, 14 µm long, and the other a short one, 3 µm
486
J. M. Lee and C. Y. Chang
Table 1.
Character comparison of two new Ptychostomella species with known congeners.
Body Length
(µm)
P.
pectinata
P.
ommatophora
P.
mediterranea
P.
helana
P.
tyrrhenica
P.
bergensis
P. lepidota
P.orientalis
n. sp.
P. papillata
n. sp.
220
360
190
700–800
170–180
320–360
280–300
264
234
embossed
with
hemispherical
elevations
terraceshaped
cuticular
protrusion on
head; papillae
with sensory
hair(s)
Cuticular
armature on
dorsal
surface
smooth
smooth
smooth
smooth
smooth
smooth
cuticular
elevations
Tentacle
absent
absent
1 pair
(knoblike)
1 pair
(clubshaped)
1 pair
(knob-ike)
absent
absent
1 pair
(knob-like)
absent
Eyespot
absent
present
absent
absent
absent
absent
absent
absent
absent
TbA
(per side)
5
4
4
5–8
4
7
6
3
5–6
TbL
(per side)
2
4
2
absent
2
2
2
2
3
Foot (TbV)
absent
absent
–
absent
absent
1 pair
(of 4
tubes)
1 pair
(of 4–5
tubes)
2 pairs
(of 2–3 tubes)
absent
TbVL
(per side)
7
12–16
–
absent
6
9
9
1
20
Pedicle
bifid
bifid
trifid
absent
bifid
bifid
bifid
bifid
bifid
Copulatory
organ
pyriform
–
–
–
bladderlike
pyriform
pyriform
oblong
weakly
pyriform
Distribution
North Sea
(Germany),
Baltic Sea
(Poland)
North Sea
(Germany,
Norway)
Mediterranean
(Italy)
Baltic
Sea
(Poland)
Mediterranean
(Italy)
North
Sea
(Norway)
North Sea
(Norway)
NW Pacific
(Korea)
NW Pacific
(Korea)
long); third pair implanted more laterally; penultimate one
(U92) situated just ahead of the third TbL; last papillae issuing from dorsal surface of caudum at the base of bifurcated
pedicle.
Ventrolaterally, 12 subconical papillae per side evenly
spaced along nearly whole length of body (U12-U87) each
with 1 long sensory hair (ranging 9–13 µm long); comprising
2 anteriormost papillae lateral to TbA, 2 in mid-pharyngeal
region, 2 around PhJIn, and remaining 6 papillae in trunk
region (U51-U87). A pair of small papillae present on ventral
side near pharyngeal pore (U36).
Eyespot lacking. Epidermal glands 15–16 per side
aligned along body length from U13 to U90, generally oval
in shape, mixed in size (4–7 µm in diameter). The openings
of anteriormost glands (Fig. 6B) can be seen dorsolaterally
along the second transverse ridge.
Ventral cilia arranged in transverse rows that cover the
whole ventral surface, from just behind the anterior adhesive
tubes to the base of caudum.
Adhesive tubes: TbA 5–6 per side (ca. 6–10 µm long),
forming an arc behind oral opening at U12-U16, of which 3
tubes ventrally and 2–3 ventrolaterally. TbVL 20 per side,
located somewhat ventrally, rather slender and ranged from
ca. 6 to 12 µm in length; foremost one at U20, and remaining tubes more or less evenly distributed in intestinal region
from U46 to U84. TbV absent. TbL shown as hollow, cuticular tube without granular content (apparently not cirratumtype); 3 TbL per side, first tube 6 µm long, situated just
behind PhJIn at U46, second one 8 µm long, at an anterior
third of trunk (U63), and third one 10 µm long, at posterolateral edge of body (U93), approaching to lateral TbP. TbP,
up to 8–9 per side, forming a pedicle poorly developed, with
2 distal (8 µm long), 1 medial (6 µm long) and 5–7 lateral
tubes (ca. 5 µm long).
Reproductive apparatus: A single testis on right side, its
anterior end reaching far behind PhJIn (U49). Vas deferens
coiled or folded at the level of anterior tip of copulatory
organ (U74), joining copulatory organ at posterior end. Copulatory organ weakly pyriform, narrowing posteriorly (14 µm
X 40 µm, 06U X17U), located in U73-U90, wrapped with thin
muscles spirally. Seminal receptacle appeared suboval, just
ahead of copulatory organ, and containing several spermatozoa. Spermatozoa apparently filiform. One large ovum situated dorsally in mid-intestinal region (ca. 58 µm X 24 µm).
Specimens collected in medium sands on sublittoral
bottom (12 m depth).
Ptychostomella Gastrotrichs from Korea
487
Fig. 5. Ptychostomella papillata new species. A, habitus, dorsal; B, habitus, ventral; C, juvenile, dorsal; D, juvenile, ventral. Scale bars=30
µm.
Description of juvenile: A juvenile (Fig. 5C, D) 135 µm
long; pharynx 49 µm long. Compared with adults, the juvenile specimen possessed nearly all the characters of adults
in general, except that the number of papillae and adhesive
tubes were fewer, and pharyngeal pore not clear. The terrace-shaped cuticular protrusion was composed of 5 projec-
488
J. M. Lee and C. Y. Chang
Fig. 6. Ptychostomella papillata new species. A, habitus, ventral.
Nomarski optics; B, head, dorsal. SEM micrographs. Scale bars:
A=30 µm; B=10 µm.
tions as in adults. However, a pair of papillae on dorsal ridge
behind it were not detected. Only 4 small papillae per side
situated on dorsal surface at U27-U87. Single papilla near
posterior edge of trunk was absent. Dorsolateral papillae
consisted of 8 pairs per side, including anterior 4 in pharyngeal region, 3 in intestinal region, and 1 on caudum; fore-
most one single, second and fourth pairs of 3 papillae, and
others of 2 papillae; third pair situated rather laterally as
compared with that of adult specimens. Ventrolaterally, 9
subconical papillae were present per side, each with 1 long
sensory hair; first 4 papillae located at pharyngeal region,
fifth one at PhJIn, and remaining 4 papillae including the last
one beside third TbL, inserted in intestinal region. TbA consisted of only 3 pairs, lacking ventrolateral ones. TbVL was
composed of only 4 tubes per side, first one (7 µm long)
located in the pharyngeal region at U24, and other 3 tubes
(8–10 µm) in the mid-intestinal region at U58, U66 and U72,
respectively. Each pedicle was furnished with 2 distal TbP
flanking only 1 medial and 1 lateral tube.
Measurements and variability: Body lengths of 12
adult type specimens in glycerin ranged from 218 µm to 266
µm (mean 230 µm, standard deviation 13), maximum widths
48–67 µm (21U-27U). The location and number of small
papillae on dorsal surface were rather variable as 6-8 per
side. The number of dorsolateral and ventrolateral papillae
pairs were somewhat variable, ranging 10–13 and 12–15,
respectively; dorsolateral papillae showed the symmetrical
arrangement, but ventrolateral ones were sometimes asymmetrical. The arrangement and number of adhesive tubes
also showed some variability. TbA was almost composed of
5–6 pairs, however, one paratype had 7 pairs, and another
specimen 4 tubes on one side and 5 on the other. TbVL in
the pharyngeal region was consistently single, but the number of TbVL in intestinal region was much variable, varying
from 12 to 20 per side, and often showed the asymmetrical
arrangement. Each pedicle was furnished with 2 distal and
1 medial TbP in all specimens examined, while the number
of lateral tubes was variable, ranging 5–7.
Etymology: The specific name papillata (papillatus, L.
meaning “of papilla” or “with papilla”) refers to the possession of numerous papillae, the decisive feature differentiating this species from all the congeners.
Remarks: The new species is unique in having the terrace-shaped cuticular protrusion on head and the numerous
papillae arranged in bilateral columns on dorsal, dorsolateral
and ventrolateral surface.
Ptychostomella mediterranea Remane, 1927, P. helana
Roszczak, 1939 and P. tyrrhenica Hummon, Todaro and
Tongiorgi, 1993 differ form the new species in bearing (clubshaped or knob-like) cephalic tentacles and less than two
pairs of TbL (against three pairs of TbL in P. papillata).
Moreover P. papillata has the pedicle with two distal tube,
while P. mediterranea bears the pedicle with three distal
tubes, and P. helana lacks the pedicle altogether.
Ptychostomella papillata is closely allied with P. pectinata Remane, 1926 and P. bergensis Clausen, 1996 in
sharing the absence of cephalic tentacles and eyespots,
and the bilobed caudum, but it is discernible from them in
possessing more TbL (three tubes per side against two both
in P. pectinata and P. bergensis) and TbVL (20 tubes per
side in P. papillata), and a relatively longer copulatory organ
than in P. pectinata and P. bergensis. Moreover, P. papillata
Ptychostomella Gastrotrichs from Korea
lacks the group of seven tubes near first TbL in P. pectinata
as well as the foot-type TbV in P. bergensis. On the other
hand, P. ommatophora Remane, 1927 has a pair of eyespots and four pairs of TbL.
Based upon the character comparison table (Table 1),
a key to the species of genus Ptychostomella Remane is
prepared as follows.
A key to the species of genus Ptychostomella Remane
1. Dorsal surface smooth .................................................... 2
Dorsal surface embossed with hemispherical elevations
......................................................................................... 6
Dorsal surface with terrace-shaped cuticular protrusion
on head and numerous papillae with sensory hair(s) ......
............................................................... P. papillata n. sp.
2. Eyespots present........... P. ommatophora Remane, 1927
Eyespots absent ............................................................. 3
3. With paired club-shaped tentacles..................................
................................................. P. helana Roszczak, 1939
With paired knob-like tentacles ...................................... 4
Without cephalic tentacles .............................................. 5
4. Pedicle with 3 distal TbP.................................................
........................................ P. mediterranea Remane, 1927
Pedicle with 2 distal TbP.................................................
........P. tyrrhenica Hummon, Todaro and Tongiorgi, 1993
5. With a pair of foot-type TbV; TbVL evenly spaced in trunk
region.................................... P. bergensis Clausen, 1996
Without foot-type TbV; TbVL gathered near first TbL ....
............................................... P. pectinata Remane, 1926
6. With paired knob-like cephalic tentacles.........................
.............................................................. P. orientalis n. sp.
Without cephalic tentacles ...... P. lepidota Clausen, 2000
489
Antonio Todaro for their critical review. We are grateful to J. W.
Choi and Y. H. Song for their help in collecting samples. This work
was supported by Korea Research Foundation Grant (KRF-2002070-C00080).
REFERENCES
Chang CY, Lee JM, Clausen C (1998a) Description of two new species thaumastodermatids (Gastrotricha, Macrodasyida) from
Korea. Korean J Biol Sci 2: 315–321
Chang CY, Lee JM, Clausen C (1998b) Two new species of Thaumastoderma (Gastrotricha, Macrodasyida) from Korea. Sarsia
83: 329–336
Chang CY, Lee JM (2001) Two new Tetranchyroderma gastrotrichs
(Macrodasyida Thaumastodermatidae) from South Korea.
Korean J Biol Sci 5: 187–194
Chang CY, Kubota S, Shirayama Y (2002) New marine gastrotrichs
of the family Thaumastodermatidae (Gastrotricha: Macrodasyida) from Shirahama, Japan. Pro Biol Soc Wash 115: 676–688
Clausen C (2000) Gastrotricha Macrodasyida from the Tromsø
region, northern Norway. Sarsia 85: 357–384
Lee JM, Chang CY (2002) Pseudostomella gastrotrichs (Macrodasyida, Thaumastodermatidae) from South Korea, with a brief
review of the genus. Korean J Biol Sci 6: 207–213
Remane A (1926) Morphologie und Verwandtschaftsbeziehungen
der aberranten Gastrotrichen I. I Z f Wiss 5: 625–754
Ruppert EE (1988) Gastrotricha. In “Introduction to the study of
meiofauna” Ed by RP Higgins, H Thiel, Smithsonian Institution
Press, Washington DC, pp 302–311
Ruppert EE (1991) Gastrotricha. In “Microscopic Anatomy of Invertebrates, : Aschelminthes” Ed by FW Harrison, EE Ruppert,
John Wiley & Sons, New York, pp 41–109
Saito I (1937) Neue und bekannte Gastrotrichen der Umgebung von
Hiroshima (Japan). J Sci Hiroshima Univ 5: 245–265
Shirayama Y, Kaku T, Higgins RP (1993) Double-slided microscopic
observation of meiofauna using an HS-slide. Benth Res 44: 41–
44
(Received June 17, 2002 / Accepted December 18, 2002)
ACKNOWLEDGEMENTS
Sincere thanks are due to Dr. William D. Hummon and Dr. M.