Reproductive cycle of Scrobicularia plana (da Costa, 1778) (Bivalvia: Semelidae) in two Moroccan lagoons: Khnifiss and Oualidia

The gametogenic cycle of Scrobicularia plana (da Costa, 1778) (Mollusca: Bivalvia) was studied in two Moroccan lagoons, both of them exposed to upwelling influence but with different climate and environmental characteristics (Oualidia located in Centre near an industrial area, and Khnifiss in saharian zone). The gonadal development was studied in both populations by histology and gonadic index. At both lagoons, the sex ratio averaged 2:1 in favor of females (at Oualidia, ÷²= 36.4150; df= 24; p= 0.05, and at Khnifiss, ÷²= 31.4104; df= 20; p= 0.05). The gametogenesis cycle began at Oualidia in September, while at Khnifiss in October. Two periods of spawning in spring and summer months were observed in both sites with small differences. Gonadic index never reached the value 1, and in the gonad of all individuals different stages of gametogenesis were foun