Macroparasites of megamammals: The case of a Pleistocene-Holocene extinct ground sloth from northwestern Patagonia, Argentina

摘要

Sloths and ground sloths (Xenarthra: Tardigrada) are among the most conspicuous mammals in the Cenozoic faunas of South America. During the late Pleistocene and the early Holocene, all the megafaunal xenarthrans became extinct. While much attention has been paid to understanding the causes of megafauna extinction, less attention has been given to understanding the impacts of the loss of the megafauna on other organisms with whom they interacted. Paleoparasitology offers the opportunity to look back into the past and observe directly how parasites responded to environmental change and host decline events. The present work is the first pale-oparasitological study on megaherbivores dung from the archaeological site Cueva Huenul 1 (northwestern Patagonia, Argentina). Twenty one dung samples were examined for parasites. Samples were processed by rehydration in a 0.5% water solution of trissodium phosphate, followed by homogenization, filtered and processed by spontaneous sedimentation. Additionally, microhistological analyses of three samples were made. The dung samples were identified as belonging to a ground sloth. Ground sloths from northwestern Patagonia were infected by the nematodes Trichostrongylus sp., Nematodirus sp., at least three Strongylida-type species, Trichuris sp., one ascaridid and one unidentified nematode. Also, the results indicated that the diet was mainly based on shrub species (Schinus johnstonii, Prosopis sp., Berberis empetrifolia, Ephedra chilense and Retanilla patagonica), typical of the Monte vegetation. Also, the cacti Maihuenia and the grasses Festuca kurtziana, Hordeum comosum, Stipa speciosa and Poa sp. (Family Poaceae) were found but in less frequency. The host-parasite-environment interactions, the potential parasitic diseases and ecological consequences of the ground sloth extinction are discussed. This study shows the potential of paleoparasitological studies of ancient feces to contribute to the understanding of the evolutionary histories of parasites and hosts.