Reproductive Periodicities of Indo-Pacific Invertebrates in the Gulf of Suez.

III. The Echinoid Diadema Setosum (Leske)

Gametogenesis occurs between April-May and August in populations of D. setosum in both the Gulf of Suez and the northern Red Sea. Spawning occurs between early June and mid-September. Both a “critical” minimum sea temperature of about 25°C and accumulation of nutrients in the gonads seem important for the regulation of gametogenesis. High temperatures in summer may limit gametogenesis by preventing accumulation of nutrients. Close gametogenic synchrony among individuals within discrete populations suggests the presence of a spawning rhythm. The lack of gametogenic synchrony among different populations, however, indicates that the spawning rhythm, if present, has little direct relation to lunar cycles.