Reproductive cycle and gonadial changes in the New Zealand rock oyster Crassostrea glomerata

Abstract

The annual reproductive cycle and the cyclical changes in the gonad of theNew Zealand rock oyster, Crassostrea glomerata (Gould, 1850), during thebreeding period of 1970-71 and 1971-72 have been described. The gonad passesthrough an intermediate phase, after a post-spawning period, when sex is indeterminate.Gametogenesis begins in July and August, but follicles ripen mostlyduring the spring months of October and November. Maximum development isseen in November, and nearly all oysters are in spawning condition in Decemberand January. Major spawning takes place in January or February dependingupon water temperature, and spawning continues until the end of March. Larvaemay be found in the- plankton until late in the season, to the end of April oreven May. Following spawning, gonadial regression sets in, with leucocyteinfiltration and phagocytosis of residual gonial cells. A greater percentage ofoysters more than 1 y old are females. The majority of oysters of age 1 y andbelow are males. © 1974 Taylor & Francis Group, LLC.