Abstract The present study is the first report of Spiroxys larvae parasitizing stomach and intestine of three fish species in stream of Caatinga domain, Northeast, Brazil. A total of 120 fish specimens, 40 of Astyanax bimaculatus, 40 of Hoplias malabaricus, and 40 of Hoplosternum littorale were examined for nematodes. A total of 633 specimens of Spiroxys larvae were recovered for the three fish species: 227 in A. bimaculatus (prevalence (%) = 48; mean abundance = 5.78 ± 1.78 (range = 0–70); and mean intensity = 11.95 ± 2.7 (range = 2–70)), 176 in H. malabaricus (prevalence (%) = 42.5; mean abundance = 4.40 ± 1.55 (range = 0–53); and mean intensity = 10.35 ± 2.38 (range = 2–53)) and 230 in H. littorale (prevalence (%) = 42.5; mean abundance = 5.75 ± 1.98 (range = 0–52); and mean intensity = 13.53 ± 3.04 (range = 1–52)). This study expands the range of the geographic distribution of nematodes of the genus Spiroxys and increase the list of hosts, as well as contributing to the knowledge of fish parasites biodiversity in Caatinga domain.

ABSTRACT The present study describes Tereancistrum flabellum n. sp. (Dactylogyridae, Ancyrocephalinae) from the gills of the anostomid fishes Leporinus friderici, Leporinus amblyrhynchus and Leporinus elongatus from two freshwater ecosystems in the south east of Brazil. This new species is mainly characterized by the morphology of the copulatory complex (such as the MCO base formed by two fan-shaped structures, and accessory piece flattened, curved, rigid and channeled), a dorsal anchor with a well-developed superficial and inconspicuous deep root, and the shape of the accessory anchor sclerite with small spathulate termination. Tereancistrum flabellum n. sp. is the first record of a dactylogyrid from L. amblyrhynchus. The description of Tereancistrum parvus is also emended to correct and complement previous descriptions and the species is reported for the first time in Schizodon nasutus.

ABSTRACT The degradation and homogenization of natural habitats is considered a major cause of biotic homogenization. Many studies have been undertaken on the effects of dams on aquatic wildlife, in particular fish assemblages. But how do dams affect the parasitic fauna of such fish? The aim of the present study was to examine parasitic similarity, comparing the diversity and structure of parasite communities of Leporinus friderici (Characiformes, Anostomidae) in three upstream tributaries under the influence of the Jurumirim Dam on the Upper Paranapanema River in southeastern Brazil. The present study did not find any significant differences in parasite communities among populations of L. friderici in the three upstream tributaries. This result highlights that dams promote and facilitate the dispersal of organisms between localities, and therefore the spatial homogenization of parasite communities. Overall, the results suggest that fish parasite assemblages can provide suitable data for evaluating biotic homogenization caused by dams.