Estudo paleoparasitológico em icnofósseis de aves da formação Tremembé (Oligoceno da Bacia de Taubaté), São Paulo, Brasil

Abstract

Coprolites are promising tools for the understanding of paleoecological and paleoenvironmental aspects. Through its chemical composition and analysis of microand macrostructures, it is possible to obtain information about the diet of ancient animals and insights into the climate and vegetation of paleoenvironments. Paleoparasitological analyzes of these trace fossils help to understand the parasite-host relationship and how parasitic infections were processed in the past. The present study aims to identify helminths in coprolites of the Tremembé Formation (Oligocene of the Taubaté Basin, São Paulo), housed at the Paleontology Collection of the Geology Faculty, Rio de Janeiro State University (UERJ). Furthermore, we included the descriptive association of the paleoparasitological data with the paleoenvironmental information present in the literature for this geological formation. Three to five grams of coprolites (n=20) were rehydrated in an aqueous solution of trisodium phosphate (Na3PO4) at 0.5% for 72 hours. The material was submitted to the sedimentation technique in conical sedimentation cups of 250 mL volume and kept sealed for 24 hours. Twenty slides were prepared for each coprolite sample, analyzed under light microscopy at 100x magnification, and confirmations were performed at 400x magnification. Eggs were identified through linear morphometry and morphology. Micro and macroscopic structures were analyzed, respectively, in an optical microscope and in a stereoscopic microscope to make inferences about hosts diet. analyzes revealed the presence of Nematode eggs of Ascaridida, Spirurida and Trichurida, with a prevalence of 5% for each group. The complex life cycle of some nematodes would be made possible by the wide faunal diversity of birds, fish and arthropods that inhabited the Tremembé paleolake. The low prevalence of helminths in the samples analyzed may be related to geological and biological taphonomic processes. This is the first paleoparasitological analysis of avian coprolites from the Tremembé Formation and the new helminth records created new perspectives for the studies of this geological unit through the epidemiological understanding associated with the local paleofauna and provide subsidies for the further development of evolutionary and biogeographic studies of helminths.