Helminth community of Thrichomys laurentius (Rodentia: Echimyidae) between two contrasting phytogeographic subunits of the Caatinga.

The structuring of parasite communities in small mammals depends on both host-intrinsic factors and environmental conditions. We investigated the helminth fauna of the caviomorph rodent Thrichomys laurentius, comparing populations from two contrasting phytophysiognomies in the Caatinga biome: open shrubland in Carrasco area and seasonal deciduous forest in Mata Seca area. In this context, the influence of biotic predictors (host sex and host body weight) and abiotic predictors (phytogeographic subunit: Carrasco or Mata Seca) on parasite diversity (species richness, Shannon, and Simpson indices) was evaluated, as well as the effect of habitat type on the parasite community composition of this host species. Twenty-seven T. laurentius specimens (Carrasco: n = 15; Mata Seca: n = 12) were examined for helminths. A total of seven helminth species were recovered (Heligmostrongylus almeidai, Paraheligmonella interrogans, Helminthoxys freitasi, Stilestrongylus freitasi, Stilestrongylus sp., Raillietina sp., and Aspidodera raillieti). Heligmostrongylus almeidai was the dominant species in both phytophysiognomies, sharing dominance with P. interrogans in the Mata Seca. Overall helminth infection was significantly higher in Mata Seca (100%) compared with Carrasco (53%). The phytogeographic subunit was the strongest predictor for diversity indices, followed by host sex, which influenced parasite richness, and host body weight, which influenced Shannon and Simpson diversity indices. Although Mata Seca showed higher parasite abundance, species diversity was higher in Carrasco due to lower dominance. Local physiognomic variations in the Caatinga impose environmental filters that govern geohelminth success. Additionally, this study reports the first record of Aspidodera raillieti in T. laurentius.