Reproduction in Australian Pearl Oysters (Lamellibranchia). I. Pinctada albina (Lamarck): Gametogenesis

Abstract

The primary gonad of Pinctada albina consists of paired systems of confluent tubules ("follicles") opening to the exterior at laterally situated urogenital openings. There are no morphologically differentiated gonoducts; the gonads empty into a short ciliated genital vestibule through the primary gonad follicles. A duct from each kidney enters each vestibule just inside the urogenital papilla. There is no superficial difference between the gonads of male and female, except in colour: the testis is cream and the ovary yellow.

The follicles originate in the connective tissue behind the openings, and spread through the space between external epithelium and viscera, by invagination, branching, and ramification. As they do so they carry with them, attached to the follicle walls, the primary germ cells ("stem cells"). There are four main follicular systems on each side of the body, but as development proceeds they tend to coalesce. Soon the gonad loses its bilateral appearance and envelops the whole visceral mass.

The species becomes sexually mature in its first year, often within 4 or 5 months.