A new heligmonellid (Nematoda) species of the genus Stilestrongylus in Euryoryzomys russatus (Rodentia: Sigmodontinae) in the Atlantic Forest, southern Brazil.

A new species of Nippostrongylinae (Nematoda: Heligmonellidae), Stilestrongylus rolandoi n. sp., is described from specimens collected from the small intestine of the rodent Euryoryzomys russatus in the Atlantic Forest (Santo Amaro da Imperatriz, Santa Catarina state, southern Brazil). The genus Stilestrongylus includes 23 species, which parasitize rodents occurring in the Neotropical region. Stilestrongylus aureus (Durette-Desset & Sutton, 1985) from Argentina, S. azarai (Durette-Desset & Sutton, 1985) from Argentina, S. flavescens (Sutton & Durette-Desset, 1991) from Uruguay, S. franciscanus (Digiani & Durette-Desset, 2002) from Argentina, S. gracielae (Digiani & Durette-Desset, 2006) from Argentina, and S. oryzomysi (Sutton & Durette-Desset, 1991) from Argentina are closely related to Stilestrongylus rolandoi n. sp., all having caudal bursa patterns of types 1-4 in one of the lobes. Stilestrongylus rolandoi n. sp. is distinguished from the aforementioned species by its ray 6 being short in relation to rays 4 and 5, which are long and robust, and by having caudal bursa patterns of types 1-4 in both lobes. The new species has 27 ridges in the mid-body in males, and 24 in females, and has one of the highest ratios of spicule length to body length (21-33%) in this genus.