| Budget Amount *help |
¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 1986: ¥400,000 (Direct Cost: ¥400,000)
Fiscal Year 1985: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1984: ¥1,200,000 (Direct Cost: ¥1,200,000)
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| Research Abstract |
Many sea breams are known to be functional hermaphrodits and they undertake sex change from male to female (protandry) or female to male (protogyny). However, little is known about hermaphroditism in three species of Japanese sea breams, Pagrus major, Evynnis japonica and Dentex tumifrons, in spite of their very high commercial value. The present study aimed to elucidate whether functional hermaphroditism occur in these three species or not.
Pagrus major : It become clear that female germ cells predominate in specimens of 1 year in age. When they grow to to year in age, testicular tissue start to appear on the ventral side of the ovary in some individuals. This hermaphroditic gonads change into testis by degeneration of the ovarian tissue, but the lumen which is derived from ovarian cavity remains in functional testis. Transformation from ovary to testis seemed to occur in young specimens only, and functional hermaphroditism seemed not to occur in this species.
Evynnis japonica : The feature of gonadal transformation in this species was almost same as that of P. major. It is concluded that E. japonica shows only juvenile hermaphroditism.
Dentex tumifrons : This species is said to be protogynous. Aoyama (1955,1980) found a small number of males but their origin was not known. In the present study, it become clear these young males are derived by the transformation of ovary into testes when the fish is in juvenile stages.
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