A new species of Moniliformis from a Sigmodontinae rodent in Patagonia (Argentina).

The majority of species of Acanthocephala known thus far from South America have been recorded mostly in fish and wild birds. In particular, rodents in Argentina have been poorly studied for acanthocephalans. The genus Abrothrix (Sigmodontinae-Cricetidae) ranges from the Altiplano of southern Peru through the highlands of Bolivia, northern Chile, and Argentina south through Tierra del Fuego. The purpose of this paper was to study Acanthocephala species parasitizing different populations of Abrothrix from Santa Cruz province (Patagonia Argentina). Specimens of Acanthocephala were found in the small intestine of Abrothrix olivaceus, showing values of P 14.7%, IM = 2.8, and AM = 0.41. All the rodents parasitized were collected in Punta Quilla, Santa Cruz, Argentina. The specimens of Abrothrix longipilis were not parasitized. Moniliformis amini n. sp. is described with features such as the long, cylindrical, and pseudo-segmented body; proboscis receptacle double walled, outer wall with muscle fibers usually arranged spirally, and a combination of several morphometric characters, mainly the very small size of the proboscis receptacle and length of the testes and lemnisci. A marked proportion of arthropods was found in the diet of A. olivaceus, characterizing it as arthropodivorous. Possibly, a larger sampling effort and specific projects dealing with the study of acanthocephalans will shed light on several questions of the rodent-Moniliformis relationship.