Dieta e avaliação da contaminação mercurial no jacaré-depapo-amarelo, Caiman latirostris, Daudin 1802, (Crocoddylia, Alligatoridae) em dois parques naturais no município do Rio de Janeiro, Brasil

Abstract

The freshwater system located at west area of Rio de Janeiro’s municipality is composed by two municipal natural parks: Parque Natural Municipal Chico Mendes (PNMCM) e Parque Natural Municipal Marapendi (PNMM), which are the occurrence areas of Caiman latirostris, a crocodilian species, inside municipal protection areas. These areas represent the last environments where Caiman latirostris populations still living at. Ten captures were made over a year, since June 2006 until May 2007. This species, Caiman latirostris, presents nonspecific diet, including several invertebrates and vertebrates, related to the great variability of environments where it can be found. Chico Mendes and Marapendi Natural Parks, located at Rio de Janeiro’s city, are distinct but interconnected. It was observed that alligators from Tachas’channel at Chico Mendes’ Park presented a poorer diet, composed by hexapods associated to polluted environments, than alligators from Marapendi’s pond, that include vertebrates and invertebrates organisms, mainly fishes and crustaceans, on their alimentation. The alligator’s diet at the two ponds and at Tachas’ channel was separated by length intervals. Most part of the studied animals from Tachas’ channel is fed by people that live nearby. In this study, C. latirostris didn’t show preferences on one specific prey, feeding on any possible prey available in the environment and neither any specificity on captures methods for any kind of prey. This result suggest that the prey items found in stomachal contents of C. latirostris could be a reflex of the prey’s diversity in the environment, which indicate a great adaptation capacity of this species. Due to its longevity, alligators and crocodiles are submitted to natural and anthropic environmental modifications. The species Caiman latirostris, as other crocodilians species, is considered as a top predator and key species in the environments where they live, being used as bioindicators of environmental quality. Mercury is a global pollutant and it is naturally present in aquatic ecosystems as lakes, rivers, wetlands and reservoirs. It may be available to biota and transferred throughout the trophic levels in the food chain. In this study were also evaluated mercury concentrations on blood and muscles of Caiman latirostris. Mercury concentrations in blood showed no differences among areas and among length intervals. Mercury accumulation on muscles of C. latirostris was different between areas, but no difference was found among length intervals. These differences found in those areas, may reflect distinct actual and past environmental conditions.