Duration of larval development of the Japanese mitten crab Eriocheir japonica (De Haan)

概要

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The five zoeal stages and megalopa larvae of the Japanese mitten crab Eriocheir japonica were reared using natural sea water in the laboratory at Tsuyazaki, Fukuoka Prefecture from September 1990 to July 1991. The timetable of larval development in the natural population was estimated from the results of incubation under ambient temperature. Duration of development increased as the water temperature decreased from autumn to winter, and all larvae were dead in 1st or 2nd zoea stage from December to April when water temperature was lower than 15℃. The duration of development of zoea larvae and megalopa larvae varied from 15 (hatched in June) to 89 days (November) and from 5 (emerged in June or July) to 13 days (October), respectively. Larval development is completed from autumn to winter by broods hatched from the early maturing group which spawned three times from September to December, and from spring to early summer from later maturing group which spawned three times after December. The settlement of a large number of larvae spawned by the later maturing group in early summer is expected. This estimation agrees closely with the observed settlement pattern of megalopa larvae in the upper tidal river.