山田湾産ホッカイエビの生態学的研究-II : エビの成長に伴う性発達ならびにその転換について
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概要
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The paper deals with the sex differentiation as observed in the secondary sexual characters and gonad of the “Hokkai-ebi”, and the study was made in order to know the correlation between sex development and growth of the prawn.The prawns mature as males during the first fall, six or seven months after hatching, and the majority of them reverse their sex characteristics and become true females by the second fall though a few remain as males. Subsequently all the animals turn into females by about twenty six months after hatching. The body lengths of the male, the transitional forms, and the female are under 83mm, 47-99mm and 80-109mm respectively.Both the male and female in the area where the present study was conducted are smaller than those in both Notsuke and Akkeshi Bay, Hokkaido. This may be caused by the fact that the age of maturity to be males and females is younger in the present bay than in the two places of Hokkaido, because most prawns in the Hokkaido area seem to function as males twice in succession during the first two or three years.