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Abstract
This study was performed in order to test theoretical predictions that sympatric species might show different reproductive strategies to facilitate their coexistence. The duration of precopulatory mate‐guarding behaviour, body size of ovigerous females, embryonic and postembryonic development time, fecundity, and viability of the sympatric amphipod species Hyalella pleoacuta and H. castroi were investigated under laboratory conditions (19±1°C and 12 h light/dark photoperiod). Specimens were collected with nets in autumn and spring 2004, and summer and winter 2005 in the Vale das Trutas, São José dos Ausentes County, southern Brazil, and transported to the laboratory. Both species of Hyalella showed similar reproductive strategies, especially in respect to the duration of the precopula, duration of the embryonic period, and fecundity. However, these species differed in body size of ovigerous females, duration of the postembryonic period, viability, and body size of juveniles that remained in the marsupium and those released by females. These differences in the reproductive traits of H. pleoacuta and H. castroi may facilitate their coexistence in nature.
Acknowledgements
The CNPq is acknowledged for a fellowship to the first author and financial support to the second author (Proc. 47259/2003‐3). We are grateful to Adriano Martins for his help during field work, to colleagues of the Laboratory of Carcinology of UFRGS for their assistance during field and laboratory activities, and to Dr Janet W. Reid for English language revision. This study was carried out according to state and federal laws concerning wild‐animal sampling. Contribution number 520 of the Departamento de Zoologia, Programa de Pós‐graduação em Biologia Animal, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil.