|Budget Amount *help
¥2,100,000 (Direct Cost : ¥2,100,000)
Fiscal Year 1993 : ¥600,000 (Direct Cost : ¥600,000)
Fiscal Year 1992 : ¥1,500,000 (Direct Cost : ¥1,500,000)
1. In triploid oysters, Crassostrea gigas, which had been cultured in Mangoku-Ura Inlet, Miyagi Prefecture, hermaphrodites were observed at a higher percentage than in diploids during reproductive period. The hermaphroditism was thought to result from sex reversal, male to female, which occurred just after spawning.
2. There were a few triploids of which gills contained both diploid and triploid cells.
3. Glycogen contents and glycogen synthetase activity in the gonad of triploids was higher than those of diploids during the reproductive period.
4. Estradiol-17 beta levels in the gonad of triploids was not different significantly from that of the diploids during the reproductive period.
Estradiol-17 beta has been reported to function as a female sex hormone in the Pacific oysters. Therefore the facts mentioned ablve (1, 3 and 4) suggests that other than genetical factors, nutritional levels, not hormonal levels, may affect determination of sex expression in the gonad of the Pacific oysters.