Reproductive cycle of the sea urchin Paracentrotus lividus (Lamarck, 1816) from the Moroccan western Mediterranean Sea: histology, gonadal index and size at first sexual maturity

The Moroccan Mediterranean coasts are an important habitat for ecologically and commercially valuable species such as the common sea urchin, which is part of the Echinoidea class. A study of the reproductive cycle of Paracentrotus lividus was carried out on the coast of Tangier, located in the southwestern Strait of Gibraltar in the western Mediterranean Sea, from January 2021 to February 2022. A total of 840 samples showed that 54.8% were between 50 and 60 mm, and the sex ratio oscillated around 1:1 in most months. Moreover, histological analysis has shown an annual reproductive cycle with a single spawning season from March to July, including six phases. In general, both sexes have synchronous gamete synthesis and release. However, there was no significant variation in the distribution of gametogenic cycle stages between females and males (ANOVA, P > 0.05). Furthermore, the gonadal index (GI) recorded its maximum value in April (5.4± 1.43) and the lowest in October (0.4±0.58). while the correlation test indicated a significant relationship between temperature, total chlorophyll and the reproduction cycle of P. lividus. Finally, the L50 method showed that the size at first sexual maturity was 34.32 mm for males and 34.94 mm for females. The findings of this research could be helpful for the decision-makers in order to develop a suitable strategy allowing the protection and management of this species.