Gonad maturation of the tropical abalone Haliotis varia Linnaeus 1758 (Vetigastropoda: Haliotidae)

Abstract

Gonad development of the tropical abalone Haliotis varia Linnaeus, 1758 from the Gulf of Mannar, southeast coast of India, was studied through the observation of gonad histology and analysis of gonadosomatic index. The sequence of gametogenesis was similar to previously described tropical haliotids. Gonad maturation stages were assigned to six categories and the details of different stages documented. Pre-vitellogenic oocytes were abundant in the early and late maturing ovary and were attached to the connective tissue tubules by their stalks. Vitellogenesis began when the primary oocytes reached 50 μm in diameter culminating in ripe oocytes of 180 ± 20 μm in diameter. All six gonad maturity stages were observed during the 14-month study period suggesting that gametogenesis was continuous throughout the year. The breeding season extended from December to February with asynchronous gonad development. Since active gametogenesis in this species was observed in all months, mature specimens could be produced throughout the year by induced maturation which would facilitate hatchery production.