Aspects on the reproduction of eared horse mussel, Modiolus auriculatus (Krauss, 1848) in Red Sea, Egypt

The reproductive cycle of the eared horse mussel, Modiolus auriculatus, was followed for one year from February, 2011 to January, 2012 based on 240 individuals collected from Hurghada, north coast of Red Sea, Egypt. The gonadal maturation of M. auriculatus was examined by means of macroscopic and histological preparations of the mantle. Annual cycle with periods of growth, maturity and discharge of gonadic products occurs simultaneously in both sexes. Ripe individuals were observed throughout the year. The largest number of spawning for the individuals occurred from March to June and July for the population. So, it was clear to identify one heavy spawning period for this species. Sexation of M. auriculatus did not differ significantly from 1:1. Sexes were distinguishable in all individuals at the ripe stage with a shell length greater than 3.00 cm. A direct positive correlation was observed between gonad index and water temperature.