モクズガニ Eriocheir japonicus (DE HAAN)の海域における繁殖生態

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  • Reproductive Ecology of the Japanese Mitten Crab Eriocheir japonicus (DE HAAN) in Its Marine Phase

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Abstract

福岡県宗像郡津屋崎町における採集・飼育結果をもとに,モクズガニEriocheir japonicusの海域における繁殖生態を明らかにした.モクズガニは雌雄とも9月初旬から7月初旬にかけて採集された.雌は全て成体であり,抱卵個体は全ての月にみられた.採集個体の甲幅組成は,生きている個体と斃死個体の間に差は認められなかった.飼育個体は雌雄とも,脱皮・成長せず8月までに全てが死亡した.死亡には11月から12月にかけてと4月から6月にかけての2回のピークが認められ,海域で斃死個体が採集された時期とほぼ一致していた.以上の結果により,9月以降海域へ回遊してきた個体のうちほとんどが,繁殖活動後脱皮・成長せず8月までに死亡することが推定された.雌には最高3回の産卵と孵化が観察され,卵塊の量は産卵回数を重ねるに従い減少する傾向が認められた.また産卵および死亡の時期が異なる2群の存在が示唆され,早期に海域に出現する個体が大型である傾向が認められた.
The reproductive ecology of the Japanese mitten crab Eriocheir japonicus in the sea was investigated by sampling and rearing crabs from Tsuyazaki, Fukuoka Prefecture, Japan, in 1990 -1991. Crabs, including ovigerous females, were collected in the field from early September to early July. Carapace width distributions for field-collected dead and live specimens did not differ. Crabs of both sexes reared in the laboratory died without moulting by August. These deaths were concentrated in two periods - November to December and again in April to June; this agreed with the periods of collection of dead crabs in the sea. Therefore, in the sea most crabs seem to die after reproduction without further moulting and growth. Female crabs oviposited and hatched eggs up to a maximum of three times. The volume of the egg mass tended to decrease in later ovipositions. There seemed to be two groups that differed in the timing of oviposition and death. Crabs that migrated to the sea in September and October tended to be larger than those migrating later.

Journal

  • BENTHOS RESEARCH

    BENTHOS RESEARCH 49 15-28, 1995-08-31

    JAPANESE ASSOCIATION OF BENTHOLOGY

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