Reproductive cycle of the rugose pen shell, Pinna rugosa Sowerby, 1835 (Mollusca: Bivalvia) from Bahia Concepcion, Gulf of California and its relation to temperature and photoperiod

This study describes, through monthly histological examinations of gonadal tissue samples, the reproductive cycle of Pinna rugosa and relates gametogenesis to temperature and photoperiod. Monthly gonadal samples were obtained from February 1993 to February 1994, in Bahia Concepcion, Gulf of California, Mexico. Five stages of gonadal development were characterized: indifferent, developing, ripe, partially spawned, and spent. Histological evidence revealed hermaphroditism in 20.9% of animals sampled. Gametogenesis commenced in March, with ripe and spawning stages occurring from April to November, and no gametogenic activity occurring from December to February. From March to November, water temperature ranged from 20 °C to 31 °C, with an average range of light of 650-820 min/day. P. rugosa had a seasonal gametogenic cycle directly related to water temperature and photoperiod.