The Study on Mechanism of Sex Determination in the Pacific Oyster, Crassostrea gigas

1993 Fiscal Year Final Research Report Summary

• Project/Area Number: 04660195
• Research Category: Grant-in-Aid for General Scientific Research (C)
• Allocation Type: Single-year Grants
• Research Field: General fisheries
• Research Institution: Tohoku University
• Principal Investigator: MATSUTANI Takeshige Tohoku Univ. Fac. of Agr., Associate Prof., 農学部, 助教授 (90134030)
• Project Period (FY): 1992 – 1993
• Keywords: Crassostrea gigas / Triploid / Gametogenesis / Sex / Glycogen / Estradiol-17 beta

Research Abstract

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.