Sesarmid crabs were widely found from the vicinity of the house standing along the river side to the estuary. The crabs living at the vicinity of the house were limited to S. (H.) haematocheir, S. (H.) dehaani and S. (S.) intermedium. From the observation of these crabs, their habitats, mating habits and other reproductive status were cleared in the present paper as follows: 1) The authors reported on the habitats of 5 species of sesarmid crabs, S. (H.) haematocheir, S. (H.) dehaani, S. (S.) intermedium, S. (P.) erythrodactylum and S. (P.) pictum, and also on the correlation between the nest hole and crabs found in the active or hibernating period. 2) By the survey of the distribution at a small river, following three types of distribution were all owed. a. S. (H.) haematocheir, S. (H.) dehaani and S. (S.) intermedium distributed up to the upper region of the river where was not effected by the sea water, but the population density of S. (S.) intermedium declined to the low density in this small river. b. It seemed that S. (P.) erythrodactylum and S. (P.) plicatum distributed only in the brackish water and were not found in the fresh or sea water region. c. Contrary to the crabs, such as S. (H.) haematocheir and S. (H.) dehaani, S. (P.) pictum inhabited the comparatively high salinity region at the sea shore throughout the year. 3) Observing the ecdysis of S. (H.) haematocheir, they proved the time from the beginning to the end of exuviation and the growth after the molting. 4) The pairing of sesarmid crabs continued from the middle of May to that of July. Though the male individual paired with the female by day and by night, the frequency of mating was higher at night than at daytime. 5) The mating habit of sesarmid crabs seemed to be similar to that of the other grapsoid crabs, but the male crab took the place below the female when the mating was disturbed by other animals. 6) It was proved by the periodic collection of the crabs that the sesarmids crabs carried their eggs on the abdominal appendages from the end of May to that of September but this period varied according to species and the size of ovigerous crabs differed from individual to individual.
ベンケイガニ類は人間社会と深い関係をもつ河川流域の家屋周辺から河口にいたるまで広く分布し,人家近くに生息するカニとしてはアカテガニ,クロベンケイ,ベンケイガニの3種に限られる.本報ではベンケイガニ類の生息場所や分布を検討し,さらにこれらのカニの繁殖についての知見をのべた.以下これらについて要約してみる. 1) ベンケイガニ類5種S. (H.) haematocheir, S. (H.) dehaani, S. (S) intermedium, S. (P.) erythradactylum, S. (P.) pictumの生息場所についてのべ,またこれらのカニと活動期や冬眠期における巣穴との関係についても言及した. 2) 小さな川での分布調査から,本類を次の3つの分布型に分けた. a. アカテガニ,クロベンケイ,ベンケイガニは海水の影響を受けない上流までみられるが,ベンケイガニは分布密度が低く生息場所も制限される. b. 汽水にのみ分布する種類としてアカツメガニ,クシテガニがあげられ,これらのカニは淡水や塩分濃度の高い海岸には生息しないようである. c. アカテガニのようなカニとは逆に,カクベンケイは活動期・冬眠期を通して比較的塩分濃度の高い海岸線に分布する. 3) 主にアカテガニで脱皮について観察し,脱皮時間や脱皮後の成長などが明らかにされた. 4) ベンケイガニ類の交尾は5月中旬から6月中旬に行なわれ,昼夜ともにみられるが,夜間に多く観察される.5) 交尾習性は他のイワガニ科のカニに類似するが,本類の雄個体は必らずしも雌の下側に位置せず,他の動物に邪魔される時にのみ,雄が下になることが知られた. 6) 周期的に各種についての採集を試み,個体群としての抱卵期間を5月末から9月末までとした.しかし,この期間は各種による差異がみられ,抱卵個体の大きさも種類によつて異なる.
Mendeley出力
