Reproductive Cycle of Sea Urchin Paracentrotus lividus (Lamarck, 1816) from the South Coast of Morocco: Histology, Gonads Index, and Size at First Sexual Maturity

The main objective of this study was to describe the reproductive cycle of the sea urchin Paracentrotus lividus (Lamarck, 1816) on the south Atlantic coast of Morocco. In this study, we selected three sites in the Agadir region: Sidi R’bat, Cap Ghir, and Anza to study from March 2018 to February 2019 some aspects of reproduction in this species through sex-ratio, the histological identification of the stages of sexual maturity, their monthly evolution, the evolution of the gonad index, as well as the size at first sexual maturity. The results show that at the three study sites, the sex-ratio is unbalanced in favor of females. The histology of the gonads revealed six different stages: recovering, growing, premature, mature, partly spawned, and spent. The gonadal cycle is synchronous for both sexes; histological examination confirmed the presence of spawning (March–October) in three sites. A perfect correlation observed between the gonad index, and the histological results suggest that the gonad index decreases when the individual is spawning. Temperature and photoperiod are important factors controlling the reproduction cycle. The beginning of spawning in the three sites coincides with the increase in temperature and photoperiod, which may act as environmental triggers. On the other hand, the size at first sexual maturity was ranged between 30 and 40 mm, and the values of L50 of females are higher than L50 of males signifying that males reach sexual maturity before females.