Seasonal biochemical variations in Pacific oyster gonadal tissue during sexual maturation

Abstract

The morphological profile and changes in biochemical composition of the ovary and testis of the Pacific oyster Crassostrea gigas cultured in Onagawa Bay during maturation were examined. As sexual maturity progressed, the glycogen content in the ovaries and testes decreased. The increases in the protein content in the ovaries corresponded with increases in oocyte diameters. The largest variations in gonadal lipids during sexual maturation occurred with the triglycerides. An increase in the ovary was associated with oogenesis and a decrease in the testis was associated with spermatogenesis. The RNA content of the ovaries was consistently greater than that of the testes, while the DNA content was lower. The RNA content and the RNA/DNA ratio are good indicators of sexual maturity in the ovary; the increasing RNA/DNA ratio in the ovary appears to show the rising synthetic activity of vitellin as one of the proteins produced within the ovary.