Reproductive aspects of the caridean shrimp Atya scabra (Leach, 1815) (Decapoda: Atyidae) in São Sebastião Island, southwestern Atlantic, Brazil

The caridean freshwater shrimp Atya scabra is a common resident of stream systems of tropical rainforests in America, including Brazilian drainages. This shrimp has an amphidromous life cycle, which increases its vulnerability when facing habitat fragmentation. Since information on the reproduction of this species is still limited, we present here data on egg production, egg loss, and energy investment, to achieve a better understanding of reproductive features of A. scabra. Specimens were collected between 2006 and 2007 in São Sebastião Island, southeastern Brazil, in 13 locations. The fecundity of 21 ovigerous females analyzed ranged between 414 and 19,250 eggs, which were higher than previously reported. However, the larger size of females analyzed may explain the observed intraspecific difference in egg production. During embryogenesis, egg volume and water content increased by 103 and 22.6%, respectively. The initial egg volume of A. scabra in the present study (0.027 mm³) was slightly lower, but comparable to the values reported previously from the same study area. During incubation, females of A. scabra lost 15% of their initially produced eggs. The reproductive output (average RO of 3.6%) is the first report for any atyid species. Its value is fairly low compared to other freshwater shrimps, and it is hypothesized that this might be related to a high energy investment in morphological adaptations, which allows the shrimp to cling on to the substrate in the fast flowing environment they inhabit. Additionally, the long life span, a well-known phenomenon in atyid shrimp, may allow the species to invest a relatively low amount of energy per brood in egg production, but over a longer time span