Intraspecific interactions in the mangrove crab Ucides cordatus (Decapoda: Ocypodidae) during the metamorphosis and post-metamorphosis periods under laboratory conditions

摘要

Current efforts for restocking natural populations of the mangrove crab Ucides cordatus (Linnaeus, 1763) in Brazil have focused on developing a methodology for stimulating the metamorphosis of U. cordatus larvae at a large scale. The aim of the present study was to compare the mortality rates both in individual and mass conditions, during the induction of metamorphosis of megalopa to juvenile in U. cordatus, without the use of mangrove sediment as substrate. Furthermore, the importance of intraspecific antagonistic behavior on survivorship rates during early post-metamorphosis period was investigated. Metamorphosis was induced by the use of water conditioned with conspecific adults (30 indiv. 100 L-1 for 24 hours). In the first assay, megalopae were stimulated into metamorphosis in experimental vials, both under individual and mass rearing conditions. The second assay assessed the interactions between megalopae and first instar juveniles, which have metamorphosed for more than 24 hours. In the third assay, the existence of cannibalistic behavior among first instar juveniles under different experimental densities was investigated. Significant differences between survivorship rates of individuals that metamorphosed under individual and mass rearing conditions were detected. However no cannibalistic behavior between juveniles and megalopae was observed in the second assay. Juveniles reared at a density of 200 indiv.m(-2) showed survivorship rates similar to those obtained under individual conditions. Yet 500 juveniles.m(-2) treatments showed significantly lower survivorship rates. Intraspecific interactions appear to be an important problem in U. cordatus specifically during the metamorphosis, but not during larval and post-larval rearing.