Oxyuricassis coronatus n. gen. n. sp. and O. hexaspinatus n. sp. (Oxyurida: Pharyngodonidae): Parasites of Lasiancistrus saetiger (Siluriformes: Loricariidae) in Freshwater Rivers of the Brazilian Amazon

A new nematode genus is described from intestines of Lasiancistrus saetiger Ambruster from freshwater rivers in the Brazilian Amazon. Oxyuricassis n. gen. is characterized by a cephalic cone, small buccal cavity, long esophagus with a well-developed isthmus, and a conical tail with spines. Two new species are described: Oxyuricassis coronatus n. sp. is characterized by the absence of lateral alae, a conical tail with truncated extremity with spine-like sclerotized projections around the tail tip, and caudal alae in males expanded. Oxyuricassis hexaspinatus n. sp. is characterized by lateral alae, a conical tail with tapered extremity, with 2 pairs of proximal spines at the posterior extremity of the tail, 1 dorsal pair and 1 ventral pair, plus a pair of lateral spines that vary in position between sexes, and male of O. hexaspinatus has narrow caudal alae. Both species were found co-parasitizing all of the analyzed host specimens.