Gonadal growth and gametogenesis in the sand dollar Mellita quinquiesperforata (Leske, 1778)

Abstract

Gonad indices of Mellita quinquiesperforata (Leske), (wet wt gonad/wet wt whole animal) × 100, were highest in January and February (1.9%) and lowest in April and May (0.6%) with smaller animals generally having less gonad/g wet wt than larger animals. The gonad may increase due to proliferation of nutritive material without production of gametes as in summer 1973. Animals attaining sexual maturity at or near one year of age spawn asynchronously. Older individuals tended to spawn synchronously over a period of one to two months. Young oocytes are present during all phases of gametogenesis. Medium size oocytes are phagocytized in later stages. Ripe eggs may be held in the ovary lumen for up to one month. Phagocytosis may terminate gametogenesis prematurely.