Abstract
The life history and reproductive activity of the two sympatric Amphipods Deshayesorchestia deshayesii (Audouin, 1826) and Talitrus saltator (Montagu, 1808) were studied through 18 months in Bizerte beach (37 degrees 19'17.1"N; 09 degrees 51'57.3"E). During this period, 6255 and 2152 specimens, respectively, of Deshayesorchestia deshayesii and Talitrus saltator were identified. The reproductive season extended from April to November for D. deshayesii and from March to November for T. saltator, with a sexual rest period during winter for both species. During the study period, three cohorts were identified on the first sampling date for T. saltator and twelve new cohorts were detected later, while D. deshayesii has presented six cohorts on the first sampling date and twelve new cohorts were detected during the study period. The life span was estimated at 4 to 10 months and at 5 to 7 months depending on the time of birth, respectively, for D. deshayesii and T. saltator. These results suggest that the two species can be considered as a semiannual species, with iteroparous females.