VENUS 62 (3-4): 111-116, 2003

Occurence Occurence of Pisidium conventus aff.α kkesiense in Gunma Prefecture, Japan (Bivalvia: Sphaeriidae)

Hiroshi Hiroshi Ieyama1 and Shigeru Takahashi2

Faculty 1Faculty of Education, Ehime Universi η，Bun わ1ocho 3, 2 3, Ehime 790-857 スJapan; [email protected]

Yakura Yakura 503-2, Agatsuma-cho, Gunma 377 同 0816, Japan

Abstract: Abstract: Shell morphology and 姐 atomy of Pisidium conventus aff. akkesiense collect 巴d from from a fish-culture pond were studied. This species showed similarities to the subgenus Neopisidium Neopisidium with respect to ligament position and gill, res 巴mbling P. conventus in anatomical characters. characters.

Keywords: Keywords: Pisidium, Sphaeriidae, gill, mantle, brood pouch

Introduction Introduction

Komiushin (1999) demonstrated that anatomical features are useful for species diagnostics

佃 d classification of Pisidium, including the demibranchs, siphons, mantle edge and musculature, brood brood pouch, and nephridium. These taxonomical characters are still poorly known in Japanese species species of Pisidium. An anatomical study of P. casertanum 仕om Lake Biwa (Komiushin, 1996) was 祖巴arly report. Onoyama et al. (2001) described differences in the arrangement of gonadal tissues tissues in P. parvum and P. casertanum. Mori (1938) classified Japanese Pisidium into 24 species and subspecies based on minor differences differences in shell characters. For a critical revision of Japanese Pisidium, it is important to study as as many species as possible from various locations in and around Japan. This study includes details details of shell and soft p 紅 t mo 中hology of Pisidium conventus aff. akkesiense from Gunma Prefecture Prefecture in central Honshu.

恥faterials and Methods

All All specimens under study were collected on May 21, 2000 from a culture pond for char (Salvelinus (Salvelinus leucomaenis) located in Hanasaki, Katashina-mura, Gunma Prefecture. The pond is concrete- lined. The subs 仕atum of the bottom consists of deciduous leaf litter and silt. Specimens were fixed in 5% formalin and pr ，回 erved in 70% ethanol. Measurements Measurements of the shells were taken with a stereoscopic microscope using a micrometer eyepiece eyepiece and slide glass of O.lmm mesh. Measurement criteria were based on Ituarte (1996) and Komiushin (1996): shell length, shell height, shell width, beak position (shell length along perpendicular a perpendicular that line intercepts the central point of the beak and the anterior-posterjor axis), hinge hinge length (distance between cusps of lateral teeth All and PII), hinge height (breadth of hinge plate plate under the umbo) and ligament length. Shell indices based on these measurements were calculated: calculated: Height Height index: shell height/shell length Convexity Convexity index: shell width/shell height Hinge index 1: hinge length/shell length 112 112 H. Ieyama & S. Takahashi

Hinge index 2: hinge height/shell height Ligament Ligament index: ligament length/shell length

Description Description

Family Family Sphaeriidae Jeffreys, 1862

Pisidium Pisidium conventus aff. akkesiense Mori, 1938 (Fig. (Fig. 1)

Shell: Shell: Shell oval, equivalve, slightly inequilateral, moderately high, and laterally compressed. Umbones broad and slightly protruding, with orthogyrous b巴aks. Anterior and posterior margins broadly broadly rounded, ventral margin smoothly curved and convex; dorsal margin short, convex and slightly slightly curved. Shell translucent, whitish, finely striated, and only slightly porous. Periostracum light light brown with weak gloss, and usually marked by brownish sediment covering the (Fig. shell lA). lA). Hinge plate na 汀 ow; hinge length half of the shell length. Cardinal tooth C2 curves slightly, C4 straight, C3 long and bifurcate at posterior end. Lateral teeth distinctly marked. AI and AIII as well well as PI and Piil converge proximally. Ligament internal and opisthodetic; length is about 115 of of shell length (Fig. lC, D). Shell Shell measurements and indices: See Table 1. Fig. 2 shows the height or convexity index plotted plotted against shell length. Anatomy: Outer demibranch absent (Fig. lG). Branchial opening closed, so presiphonal suture is is present (Fig. lF). Inner radial mantle muscles form about five muscle bundles 紅 ranged evenly along along pedal slit in adult shell (Fig. lE). Scars of bundles separate from pallial line (Fig. IB). Inner Inner dernibranch distinguished by very short ascending lamella; brood pouch formed in lower part part of inner demibranch (Fig. IG). Nephridium of closed type, with lateral loop visible from dorsal dorsal side of body (Fig. IH). Testis located on right and ovary on left (Fig. IH). Remarks: Specimens of Pisidium conventus aff. akkesiense in the present study have the characters characters of the subgenus Neopisidium described by Odhner (1921) and Kuiper (1962); the absence absence of an outer dernibranch and branchial opening, and a non-introverted ligament. Among the the species cu 町 ently included in the subgenus Neopisidium, P. coreanum differs from this species species in having three cardinal teeth in the left valve and two in the right (Park, 1992). P. moitessierianum moitessierianum and P. syn- ψ rex (Komiushin, 2001) have umbonal appendiculae which form collar-like collar-like thickenings (Piechocki, 1989), the brood pouch placed dorsally, and nephridia with a cleft dorsal lobe. In P. forense, P. observationis and P. inacayali, the ascending lamella are well well developed (Meier-Brook, 1967 ; Ituarte, 1996 ）.百出 species is similar to P. conventus in having having a presiphonal suture and a straight inner tooth of the left valve (C2), and in the lower position position of the brood pouch, but differs in having the lateral loop running parallel to the dorsal lobe lobe and no canal parallel to the shell surface (Piechocki,1989). P. raddei, which has the same

Fig. Fig. 1. Shells and soft body parts of Pisidium conventus aff. akkesiense. A. External view of left valve. B. B. Internal view of right valve. C. Hinge of right valve. D. Hinge of left valve. E, F. M 阻 tle edge. G. G. Internal view of gill. H. Dorsal view of gonad and nephridium. Scale bar of B = 1 mm, of D = 200 μ m, of E-H = 0.5 mm. Abbreviations: Al-AIII - anterior lateral teeth, PI-Piii -posterior lateral lateral teeth, C2-C4 -cardinal teeth, aa -anterior adductor muscle, al - ascending lamella of inner demibranch, demibranch, b- brood pouch, cu - cusp of PI, d- dorsal lobe of nephridium ，巴－ exhalant siphon, i intestine, intestine, 1- laetral loop of nephridium, li -ligament, ov -ov 紅 y, pa -posterior adductor muscle, pr pr - presiphonal suture, ps - pedal slit, r- inner radial mantle muscle, sc - scar of inner radial mantle mantle muscle bundle, t- testis. P . conventus aff . akkesiense in Gunma Prefecture 113

'i;-pa 'i;-pa 114 114 H. I巴yama & S. Takahashi

Table Table 1. Shell indices of Pisidium conventus aff. akkesiense. Fyt Indices Indices Mean S.D. 一日日－－川 Height Height index 0.802 0.020 Convexity Convexity index 0.600 0.044 66468868 Beak: Beak: position index 0.554 0.029 Hinge index 1 0.525 0.035 Hinge index 2 0.046 0.006 Ligament index 0.234 0.024

0.9 0.9 z 盟国工＼工場一主nununununa え念恭二ポ約 守’ ’ 。：%。； dw£ 喝 EωPOFO 0 」＼主回一回工 ~:la ：；~ 選管0 。 Oo~議造曜夜。 。 θ 喝、大 J 。 • Height index o Convexity index 0.4 0.4 0.5 0.5 1.5 2 2.5 3 Shell Shell length (mm)

Fig. Fig. 2. Shell proportions of Pisidium conventus aff. akkesiense.

basic basic anatomical characters as P. conventus, differs from 出is species in its tetragonal shell with a broad hinge plate, markedly bent cardinal teeth, and in having the scars of the inner mantle muscles muscles fused with the pallial line (Komiushin et al. 2000). The typical P. conventus akkesiense is is di 百erent from the present specimens in its distinctly shouldered dorsal margin, almost vertically truncated truncated posterior margin, and short but wide ligament pit. Pill Pill clams (genus Pisidium) are known for their simplicity and yet shown great variability in in shell form (Korniushin, 1999), so the studied specimens are provisionally treated as Pisidium conventus conventus aff. akkesiense. If the morphological characters of P. conventus akkesiense agree with those those of the present specimens, this will prove that P. conventus akkesiense is widely distributed to to the eastern Japan. P. P. conventus aff. akkesiense in Gunma Prefectur 巴 115

Acknowledgements

We wish to thank Dr. Reginald B. Gillmor for reading the manuscript and making helpful comments. We also thank Mr. Yasumi Takahashi for directing us to a locality for pill clams.

References

I飢紅te, C. F. 1996. Argentine species of Pisidium Pfeiffer, 1821, and Musculium Link, 1807 (Bivalvia: Sphaeriidae). Sphaeriidae). The 怜 liger 39: 189-203. Korniushin, Korniushin, A. V. 1996. Morphometrical and anatomical characteristics of Pisidium casertanum (Poli) (Poli) from the Lake Biwa (Japan)(Bivalvia: Eulamellibranchiata: Pisidiidae). Malakologische Abhandlungen 18: 53-57. Komiushin, Komiushin, A. V. 1999. Anatomical investigation and taxonomic revision of pill clams of the genus Pisidium Pisidium s.l. (Bivalvia: Sphaeriidae) in the Palaearctic region. Malacological Review, Supplement 8: 69-81. 69-81. Komiushin, Komiushin, A. V. 2001. Taxonomic revision of Pisidium punctatum Sterki, 1895 (Bivalvia: Sphaeriidae). Malacologia Malacologia 43: 337-347. Komiushin, Komiushin, A. V., Krstanovski, Z. & Kostoski, G. 2000. Anatomical evidence of close affinity between endemic species of Pisidium (Bivalvia, Spha 巴riidae) from som 巴 ancient lakes, and th 巴 widely distribut 巴d taxa. Journal of Zoological Systematics and Evolutionary Research 38: 81 86. Kuiper, Kuiper, J. G. J. 1962. Note sur la systematique des pisidi 巴s. Journal of Conchyliologie 102: 53-57. Meier-Brook, Meier-Brook, C. 1967. Pisidium forense, a new sp 巴cies from Brazil (Mollusca; Eulamellibranchiata; Sphaeriidae). Sphaeriidae). Archiv 戸r Hydrobiologie 64: 63-68. Mori, Mori, S. 1938. Classification of Japanese Pisidium. Memoirs イthe Colledge of Science, Kyoto Imperial Universi η， Series B, 14: 255-278, pls. 7-l l. Odhner, Odhner, N. H. 1921. On some species of Pisidium in the Swedish State Museum. Journal of Conchology 16: 16: 218-223. Onoyama, R., Noda, Y., Takada, H. & Ieyama, H. 2001. Gonad structures in two speci 巴s of Pisidium (Bivalvia: (Bivalvia: Sphaeriidae ）.怜 nus 60: 183-188. Park, Park, J. C. 1992. Taxonomic study of Musculium japonicum and Pisidium (Neopisidium) coreanum (n. sp. ）ザSphaeriidae (Pelecypoda ；怜neroida) in Korea. Dissertation of M. Sc. of Kangwon National University, University, vi+50pp, 4pls. Piechocki, Piechocki, A. 1989. The Sphaeriidae of Poland (Bivalvia, Eulamellibranchia). Annals Zoologici 42: 249-320. 249-320.

(Received (Received March 17, 2003 I Accepted September 26, 2003) 116 116 H. Ieyama & S. Takahashi

群馬県産マメシジミの 1 種目sidium conventus aff. akkesiense

家山博史・高橋茂

要約

群馬県片品村花咲のイワナ養魚池で採集されたマメシジミ属の 1 種は Pisidium conventus aff. akkesiense と同定されたので，その形態を調べた。靭帯が内在し殻内側へ裸出しないこと，外鯉 がないことから本種は Neopisidium 亜属に属する貝であることが分かつた。また，入水開口はな いが presiphonal suture があること，内観には極めて小さい上昇葉があり，育児嚢は内鯨の下部に できることから P. conventus の特債と合致したが，腎臓側葉の位置，外套膜放射状筋の筋束痕に ついて異なっていた。 P. conventus akkesiense アッケシマメシジミの解剖学的知見はまだ報告され ておらず，また，殻の形や靭帯の形状に若干の違いが見られたので本種を仮に P. conventus aff. akkesiense とした。