Phylogenetic relationships among species of Stilestrongylus Freitas, Lent and Almeida, 1937 (Trichostrongyloidea: Heligmonellidae: Nippostrongylinae), parasites of myomorph rodents (Rodentia: Muridae) in the Neotropics

New species of Hassalstrongylus (Trichostrongyloidea: Heligmonellidae) in the large-headed rice rat Hylaeamys seuanezi, in the Atlantic Forest of northeast Brazil

A new species of Trichostrongyloidea (Nematoda: Heligmonellidae), Hassalstrongylus lauroi n. sp., is described from specimens collected from the small intestine of the rodent Hylaeamys seuanezi in the Atlantic Forest of northeastern Brazil (Igrapiúna, state of Bahia). The genus Hassalstrongylus includes 17 species, which parasitize rodents occurring in the Neotropical and Nearctic regions. It differs from the genus Stilestrongylus through its smaller number of ridges in the synlophe and through the size of the genital cone. The main taxonomic characteristics of this new species are the subsymmetrical caudal bursa of type 2-2-1, ray 8 branching out at the base of the dorsal trunk, right lobe smaller than the left, and rays 4 and 5 of robust nature. In addition, the ornamental ray 5 and the robustness of ray 4 on the male caudal bursa, along with the modification of the ridges of the posterior end of the female, allow us to consider the specimens found to be a new species.

Variation in the helminth community structure of three sympatric sigmodontine rodents from the coastal Atlantic Forest of Rio de Janeiro, Brazil

One hundred and eighty specimens of sigmodontine rodents living in sympatric conditions were collected in the Atlantic Forest in the state of Rio de Janeiro, Brazil (25Akodon cursor, 98Akodon montensisand 57Oligoryzomys nigripes) to examine whether the helminth structure and component communities can be characterized among these three closely related rodents. The parasite species richness was 9 inA. cursor, 12 inA. montensisand 12 inO. nigripes. Five species were common to the three rodent species, and eight were common toA. cursorandA. montensis. The trichostrongylids –Stilestrongylus etainA. cursor,S. aculeatainA. montensisandS. lanfrediaeinO. nigripes– were the species with highest dominance frequency and determined the characterization of individual community structures. The prevalence and abundance of concurrent helminth species among rodents were significantly different. Canonical multivariate analysis demonstrated a similar helminth community structure betweenA. cursorandA. montensisbut a high discrepancy betweenAkodonspp.and O. nigripes. Thus, the data indicated that small rodents such asA. cursor,A. montenisandO. nigripesthat are sympatric and phylogenetically related have a different community structure, but similar component community, suggesting the role of helminth specificity and the hosts' habitats as determinants in structuring their helminth communities.