The ecology of an atyid shrimp Caridina japonica was studied in the Shiwagi Rivulet. Yuki Town, Tokushima Pref. This species is amphidromous in nature. The juveniles migrate upstream from the sea exclusively during the night and can be seen climbing a vertical wall, where the rivulet water is trickling down. From field observation, rheotaxis seems, to be the most important orientation mechanism for the upstream migration of juveniles. The peak month of egg incubation was June. The mean duration of incubation was 40 days at 20℃ in aquaria. From these values and with known information on the duration of larval life, it was estimated that the period of upstream migration starts in August. Most males die within two years after metamorphosis, however, many females survive for more than two years.

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テナガエビの河口域生息群(小卵産出タイプ)と淡水域生息群(大卵産出タイプ)について,ゾエア第一期幼生の酸素消費量を種々の環境塩分濃度の下で測定した。河口域生息群では,中濃度海水中(14.2, 21.3‰S)で酸素消費は低下し,それより低い(3.5‰S)あるいは高い塩分環境(32.0%oS)で有意に上昇した。この酸素消費量の違いは,浸透圧調節作用の関与によるものと考えられた。いっぽう,淡水域生息群では低塩分環境(淡水)での酸素消費の上昇は認められるものの,高塩分環境での有意な上昇は認められず,これらの幼生は高塩分環境での浸透圧調節力を失っているのかもしれない。テナガエビ淡水域生息群の環境塩分,特に高塩分に対する反応パターンは,淡水域への進化的移行という点で,このグループが本種河口域生息群と淡水産スジエビとの中間的な段階にあることを示唆している。

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Chromosome numbers of six species of the Palaemonidae were determinated using mocified air-dry methods applied to the tesis, the regenerating biastema of the 2nd pereopod, and the ovary after the eyestalk ablation. As shown in Table 2 of the results, chromosome numbers of four species of Macrobrachium range 2n=102 and 118, and that of two species of Palaemon 2n=108 and 136. Most of the chromosomes in the examined species were metacentric and submetacentric types. And the fundamental numbers of chromosomes had wide range between these species. Considering from these results, the specific differentiation of Palaemonidae would be characterized by some possible consequence of both Robertsonian fragmentation-fusion and chromosomal rearrangements.

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ジャマイカ産淡水エビ(Macrobrachium heterochirus)の眼の明・暗順応変化を調べた。その結果明・暗順応の変化によって細胞形態の変化と同様に色素の移動も観察された。さらに,感桿(rhabdom)の先に存在する小さなレンズ様構造物を記載した。このエビは夜行性で,薄明時には大型のものの方が小型のものよりも視感度がよいことがわかった。また,眼の反射板細胞(tapetal cells)はホルモンに関係することなく直接光に反応することが示唆された。

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成熟した多数のサルエビを実験室内で産卵させ,その初期発生を観察し,他のクルマエビ科の種類と比較検討した。産卵は21:00から00:00の時刻に行われ,産卵数はおよそ6,400から106,000粒の間にあった。産卵数と頭胸甲長との相関関係はY=log(-352.215+18.6561X)(r=0.94^*)であった。卵径は産卵時には223μmであったがふ化直前には400μmに達した。水温26℃,塩分34.5の状態で産卵後15時間13分後に卵の56.4%が羊膜におおわれた状態で第一期ノープリウス幼生としてふ化した。しかし19.9%の卵はノープリウス期のまま卵内にとどまり,産卵後60時間13分を経て第一期ゾエア期に達してから10.3%の卵がふ化するのがみられた。このようなノープリウス卵とゾエア卵の出現はクルマエビ科の個体発生では初めて見出されたものである。

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The lobsterette Nephropsis stewarti beronging to the family Nephropidae, were reared in the aquarium to observe habitat behavior of redused eye crustacea. Observations carried out during 1982 to 1984. All the specimens collected at 350-400m depth of Suruga Bay, off Heda Mura. Shizuoka prefecture, Japan were carried to Shimoda Marine Station Nihon University, Shimoda-Shi. Shizuoka and reared in the 1000 liter round shaped tank with running sea water. Water temperature kept at 10-12℃. The bottom of reared tank covered with fine sand. Alive starfish caught simultaneously, frozen fish and krill, alive seaurchin, artificial diet for carp were fed. Four lobsterette specimens were reared and most longest surviving period was 112 days. Remarkable habitat were, they did not show any respons to the light and walked around on the bottom through day and night but never burrowed like other animal of the Family Nephropidae. Of the diets examined, only the starfish was fed by animals. Although the feeding behavior was not observed directly.

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Burrows of the Japanese crayfish Cambaroides japonicus (DE HAAN, 1841) in a stream in Sapporo, Hokkaido are described. The density of number of openings averaged 4.5/m^2 in ten reserch stations around the banks. The diameters of dominant particles were 0.125-0.400 mm at the central part of stations. Six resin casts of burrows showed that this species excavated a semistraight tunnel with two openings near the water surface of the stream. This tunnel was almost horizontal and was semicylindrical in cross-section with the floor flat. Some were also observed Y or T shaped burrows.

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Crayfish in Lake Mashu, Hokkaido, Japan, were captured with tangle nets in the summer of 1992. All specimens, 171 males and 517 females, had intermediate diagnostic character between two subspecies, Pacifastacus leniusculus leniusculus and P, l. trowbridgii. Although three very large individuals of unidentified crayfish were captured in this lake by poachers of trout in 1975 and 1985, there is no certain confirmation because of illegal samplings. One of the present authors took a chance to measure one of them, a fresh male crayfish with very large chelae, in 1975 when he was 11 years old and recorded only its giant size, i.e. 47 cm carapace length. However, the largest P. leniusculus collected in this study was 5.7cm in c. l. Neoteny may have occurred because there is no secondary sexual character on chelae of adult P. leniusculus males. This lake has no river. Age of the lake is estimated as about 2000 years old. Further, all species of fish and crustaceans in the lake were artificially introduced from other waters. Of crayfish, only P. leniusculus occurs and was introduced from Portland, Oregon, U.S.A., in 1930. From these, the unidentified gigantic crayfish seems to have been P. leniusculus grown to a giant size.

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The external changes with molting of a crayfish, Cambaroides japonicus (DE HAAN, 1841), were studied in aquaria. Softening and transparency of the exoskeleton, appearance of the gelatinous substance, and darkening of the body color were observed in molting. These changes appeared from five days before molting to twelve days after it. Four molting phases based on these changes and the period of them seemed to be useful to estimate the molting times in the natural habitat.

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The distributions of the phyllosoma and nisto larvae of Scyllarus kitanoviriosus HARADA were investigated in the Seto Inland Sea, Japan, in use of a small beam trawl net that was towed at 17 stations in daytime, during the period from December 1986 to November 1987. The stations were placed along isobaths of every 5 m of depth in an area shallower than 30 m in depth. Eightythree phyllosoma larvae (stages III-VIII) were caught in the season from August to November, and 32 nisto larvae only in September and October. The distribution of the stage VIII phyllosoma was identical to that of the stages III to VII. The nisto larvae appeared significantly in shallower area than the phyllosoma. Neither juvenile nor adult was caught with the trawl employed. The gillnet operated near rocky shore however, caught adults, of which the females were all ovigerous in September. This fact suggests that the last stage phyllosoma metamorphoses into the nisto in 15-25 m deep in September to October, and then metamorphoses into early juvenile stage after the settlement onto the rocky bed.

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The secondary sexual characteristics of Metacrangon angusticauda were investigated. The secondary maturation sign appeared in abdomen size in females. The number of eggs per female increases with increase of abdomen width. The number of segments of the outer and inner flagella were larger in males than in females.

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西九州天草の砂質干潟において,ニホンスナモグリの巣型をポリエステル樹脂を用いて採取した。1989年9月および1990年9月に得られた各一個の巣型では,太い成体の巣から細い巣が分岐していた。幾つかの証拠から,これらの分岐にはニホンスナモグリの新規加入個体が生息していたと推定された。着底期幼生あるいは着底後の幼稚体が成体の巣穴開口部から内部に入り込み,その途中で自分自身の巣を分岐させたと考えられる。

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Dardanus imbricatus (H. MILNE EDWARDS, 1848) is newly added to Japanese anomuran fauna, based on the single specimen collected in Okinawa Island. This hermit crab was previously recorded from Australia, New Zealand, Ceylon, the Gulf of Thailand and Vietnum. The locality recorded by the present paper is located in the northern limit of the distributional range of this species.

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Field study of reproductive activity in the ocypodid crab Ilyoplax pusilla was carried out at Tanabe Bay (33°41′N, 135°24′ E). Ovigerous females were found from April through August and most abundant in June-July. Males' sexual behaviors were observed from May through July or August and most frequent in June-July. Females were suggested to spawn or release their larvae around spring tide. Daily frequency of males' sexual behaviors did not fluctuate according to tidal condition of spring to neap tides. Proportions of waving males and wandering crabs declined in the late breeding to the nonbreeding season, indicating relation of waving and wandering to reproductive activity.

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Geographic distributions of two ocypodid crabs of the genus Ilyoplax : I. pusilla and I. deschampsi are summarized from the occurrence records in literatures and unpublished data. I. pusilla is distributed along the coast of mainland Japan and Okinawa, while I. deschampsi ranged along the continental coast of Bo Hai (Gulf of Chihle), Yellow Sea and northern East China Sea. The distributions of the two spesies overlap only at the southern coast of Korea and a part of northern Kyushu of Japan, and both species do not extend into the Japan Sea coast. Along the coast of Ariake Bay in Kyushu, Japan, where both species occurred, their distributions were investigated in detail. I. deschampsi was distributed on the innermost coast, while I. pusilla was on the coast of outer part of the bay, showing clear segregated distributions between them. In habitat conditions, there were some differences between the two species : soil hardness and coarseness of substratum, and salt content of underground water were, on the average, higher in the habitat of I. pusilla than in that of I, deschampsi.

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Twenty-one sexually paired hair crabs, Erimacrus isenbeckii (Brandt) were collected from the northwestern North Pacific, off Kushiro during August 1986 〜 July 1991. The paired hair crabs acted the precopulatory guarding behavior. Size distributions were unimodal for each ,sex but with few overlap in their carapace length (CL). The mean CL of male and female were 89.4 mm and 56.2 mm respectively. Other than the fact that males were invariably larger than females, there was no correlation between size of the male and size of the female with which it was paired. Sizes distribution of females paired with small (CL< 90 mm) and large (CL≧90 mm) size males were the same. Based on these data, we discussed size assortative mating and sexual dimorphism on the hair crab. In this species, male size is not correlated with female size in sexual pairs. However, cleary sexual dimorphism is observed.

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1990年4月12日から6月12日まで千葉県館山市の東京水産大学坂田実験実習場において,ショウジンガニPulagusia dentipesのメガロパおよび稚ガニの出現を3日おきに調査した。メガロパの磯や転石地帯への着定要因を探るために,風向,風力,月齢,水温を記録した。これら環境要因のうちメガロパの着定と強い関係の見られたものは,風向と風力であった。北の卓越風が続くとメガロパが多く磯や転石地帯に着定することが明らかになった。

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The morphological characteristics of the exoskeleton in the abult and juvenile stages of the female Japanese mitten crab, Eriocheir japonicus were recorded with reference to the shape of the abdomen, the exposure of the edges of the thoracic sternums, and the growth of hairs in the margin of the abdomen, 1st〜4th thoracic sternums, and abdominal appendages. External changes which take place during molting were also examined. During the juvenile stage (carapace measuring less than 70 mm in width), the abdomen was found to grow relatively larger, both in length and in width gradually, during pre-puberty molting. However, when the crabs were reaching the abult stage (carapace greater than 35 mm in width), the abdomen was found to drastically grow larger during puberty molting, until it nearly covered the thoracic sternums.

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American edible crab, Callinectes sapidus RATHBUN has recently been obtained from Sagami Bay. Up to now there are two reports on the occurrence of this crab in Japanese waters. The first record was accounted by SATAKI in 1976, on the basis of the specimens obtained by a fisherman in 1975 at the Hamana Lake, Shizuoka prefecture. The second one was given by ARIYAMA in 1985. He described briefly on a female crab obtained from Osaka Bay in September of 1984. This short report deals with a brief account on the third record of this crab from Japanese waters.

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The xanthid crabs, Leptodius exaratus and Cycloxanthops truncatus, Atergatis floridus, Etisus laevimanus, Pilumnus vespertilio prey on the hermit crabs. The five species of the crab employed the chelae and the ambulatory legs to capture the hermit crabs. The xanthid crabs break shell species occupied by hermit crab, Pagurus geminus.

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汽水域に生息するトゲオヨコエビ(Eogammarus kygi)の雄成体の精巣より染色体を観察した。コルヒチン処理の後,背部を切開して生体のまま組織を低張処理することにより組織の喪失を防ぎ,本種のような体長約9-17mmのごく小型の生物でもフレームドライ法によって明瞭な核板を得ることができた。染色体数は2n=56,n=28でこれとは別に微小染色体(B-chromosome)が存在した。染色体の大きさは平均16μmでほとんどの染色体が中部着糸型染色体であった。また,第一成熟分裂中期像では全ての染色体が二価染色体を形成し,性染色体の存在は認められなかった。本種の染色体数について,Gammaridaeの近縁グループおよび同属近似種の染色体数,地理的分布との関係を検討した。

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The present paper provides an annotated list of decapod fauna of Hokkaido, northern Japan, mainly based on previous biogeographical works. It includes 196 species ranging 40 families, and several new records to Hokkaido are recognized.

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鉗脚に,過剰再生体と思われる構造物を生じたアメリカザリガニProcambarus clarkii二個体を山形市郊外の沼から採集した。そのうちの一個体は,左鉗可動指の内側基部から,可動指とほぼ同じ長さの双頭の構造物が生じていた。二つの先端それぞれには正常な可動指や不動指と同様の鋸歯があった。他の一個体は,右鉗の可動指の外側基部から,長さが可動指の約60%に達する棘状の構造物が生じていた。この構造物には鉤爪や鋸歯はなかった。

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アメリカザリガニProcambarus clarkii(頭胸甲長10-18mm)の額角の殻を一部切除して過剰再生体を誘発した。傷口は3度目の脱皮で僅かに盛り上がり突起状の再生体を生じた。この再生体は,脱皮3〜4度目までは脱皮毎に伸長したが,その後は体の生長に伴って大きくなった。再生体は額角の先端部よりは基部のほうが大きくなる傾向があった。再生体の形態は先端が丸みを帯びているか,あるいは尖っていたが,これらの形態の相違はある程度は傷口の形に依存すると考えられる。

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1990年12月27日に静岡県駿河湾で獲れた雌のイバラガニモドキLithodes aequispinaが翌日水槽内で脱皮をした。脱皮にはおよそ20分間要し,脱皮15日後にへい死した。甲長は16.3cmから17.3cmに成長し,成長率は6.1%であった。脱皮前は左鉗脚は脱落していたが,脱皮後,鉗脚の再生が観察された。再生した鉗脚の長さは3.6cm,掌節は1.5cm,可動指は1.0cmであり,掌節と可動指の間には間接が認められた。

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