The reproductive cycle of the asteroid Coscinasterias muricata in Port Phillip Bay, Victoria, Australia

The reproductive cycles of two populations of Coscinasterias muricata from Port Phillip Bay, Victoria, Australia are described in terms of organ indices, oocyte development and progesterone levels. Both Governor's Reef and South Channel Fort populations exhibited clearly defined reproductive cycles with two spawning periods, during summer and during spring. In both populations, the pyloric caecal index and gonadal index showed inverse cycles suggesting nutrient translocation from the pyloric caeca to the gonads for gametogenesis. Physiological changes, such as decreases in pyloric caecal index, and increases in gonadal index and oocyte diameter were observed following the months of increased progesterone concentrations in the female pyloric caeca. These results indicate a role for this steroid in the reproductive cycle. The results from the Governor's Reef population suggest that the influence of progesterone on the reproductive cycle of female C. muricata is regulated by photoperiod. Results also provide evidence of a role for seawater temperature in the reproductive process of this species.