PRIMER REGISTRO DE SPINITECTUS RODOLPHIHERINGI VAZ & PEREIRA, 1934 (SPIRURIDA: CYSTIDICOLIDAE) EN AUCHENIPTERUS NUCHALIS (SPIX & AGASSIZ, 1829) (SILURIFORMES: AUCHENIPTERIDAE) DE LOS LAGOS DE LA LLANURA ALUVIAL DEL AMAZONAS

Fish are the vertebrates that have the greatest number and diversity of parasitic species. Auchenipterus nuchalis (Spix & Agassiz, 1829) is a small fish that occurs in South America, popularly known as “Peruvian mandi”. It has twilight habits and its diet is basically composed of aquatic insects and microcrustaceans, which are intermediate hosts of several parasitic species. Although fish are the vertebrate group with the highest number of parasitic species, most of these species are still unknown, therefore, the main objective of this study was to know and identify the Nematoda species that parasitize A. nuchalis and calculate the parasitological indices of each species. 38 A. nuchalis were captured in four expeditions in September, October, November and December 2016, in the Catalao lake complex in the municipality of Iranduba, Amazonas, on the left bank of the Solimoes river and on the right bank of the Negro river, Brazil. The fish measured, on average, 11.8 - 18 (15.1 ± 1.35) cm in standard length and weighed 30.1 – 71.0 (47 ± 10.66) g. The individuals' digestive tract was preserved in 70% ethanol and transported to the laboratory for analysis. Of the total fish collected and examined, 31 were parasitized. Temporary and permanent slides were mounted to identify the parasitic specimens. The measurements of the individuals were made with the aid of a micrometric eyepiece, coupled to an optical microscope. Eighteen individuals of Spinitectus rodolphiheringi Vaz & Pereira, 1934 parasitizing the intestine and stomach of the hosts were collected. Presenting an infection prevalence rate of 26.3%, which characterizes it as a satellite species. Furthermore, this is an unpublished record of this parasite for A. nuchalis and for the Amazon region.