Résumé:
The main objective of this study is to analyze the life characteristics of the red starfish Echinaster sepositus (18 individuals) and the common species paracentrotus lividus (27 individuals), living in the Mostaganémoise (Salamander). The choice to study these two species was motivated by the fact that the latter by their food behavior and their abundance in the environment contribute to the functioning of marine ecosystems.
Analysis of the metric parameters of the two sampled populations showed that they were both dominated by a size class of mature individuals with an average size of 12.82 mm and a mean weight of 67.20 mg in E. Sepositus and 53.47 mm with an average weight of 267.5 mg in P. lividus.
The study of the variation in reproductive biology through gonad examination and sex distribution in the two populations of echinoderma Echinaster sepositus and Paracentrotus lividus reveals that the sex ratio is in favor of females in relation to males.
Examination of the gonads showed that the starfish was in full sexual maturity and is therefore preparing for laying, whereas the Paracentrotus lividus would have emitted its gonads during this season. In addition, the evolution of the gonad index as a function of size appears proportional in the two species studied.
The examination of the digestive contents showed that for the two species Echinaster sepositus and Paracentrotus lividus, the algae represent the preferential food and more precisely the green algae for the Echinaster and the brown algae for the Paracentrotus lividus.
