Reproductive cycle of Spondylus calcifer carpenter, 1857 (Bivalvia: Spondylidae) in the "Bahía de Loreto" national park, Gulf of California, Mexico

The reproductive cycle of Spondylus calcifer from Bahía de Loreto, Gulf of California, was studied from January 1998 to March 1999. Microscopic analyses established that this species is gonochoric. The size at spawning occurred at 113-mm in shell height. S. calcifer exhibits a short spawning period from August to October followed by a long inactive period from November to February. Increase in water temperature initiates the gonadal maturation process, while decrease in water temperature inhibits gametogenesis. The threshold water temperature for spawning in S. calcifer, is 29°C. Nutrient reserves from the digestive gland are mobilized and used by the gonad during the developing stage. Meanwhile, reserves stored in the muscle are used only after gamete production has started, helping to support the energetic output during the ripe and spawning stages. In Bahía de Loreto, the period of highest phytoplankton abundance in bottom waters coincides with the onset of gametogenesis in S. calcifer. This suggests that S. calcifer also depends on food intake for oocyte growth.