A new species of Acusicola Cressey (Copepoda: Ergasilidae) from northeastern Brazil

Two new species of Acusicola Cressey, 1970 (Copepoda:Cyclopoida: Ergasilidae) parasitic on the gills of two estuarine actinopterygians off Brazil

Two new species of copepods assigned to the genus Acusicola Cressey, 1970 (Cyclopoida: Ergasilidae) are proposed based on post-metamorphic adult females, parasitizing the gills of two actinopterygian fish off Brazil namely, the Tripletail Lobotes surinamensis (Bloch) (Lobotidae), collected in the coastal zone of the State of Pará, near Curuçá Municipallity, and the Swordspine snook Centropomus ensiferus Poey (Centropomidae) collected in Sepetiba Bay, State of Rio de Janeiro, Brazil. Acusicola iamarinoi n. sp. parasite of L. surinamensis, differs from its closet congeners based on the first segment of the antennule armed with 10 setae, the presence of a maxillule armed with four elements and a pair of blunt processes dorsally on the fourth pedigerous somite. Acusicola pasternakae n. sp., collected from C. ensiferus, can be distinguished from its closest congeners based on the membranous sheath of the first endopodal segment of antenna with horizontal marks, the first segment of the antennule armed with 11 setae and a spine on the last exopodal segment of leg 2. This is the first report of representatives of Acusicola parasitizing fish of the families Lobotidae and Centropomidae as well as new geographical records of the genus in the coast of State of Pará and in Sepetiba Bay, Brazil.

Gauchergasilus euripedesi (Copepoda, Ergasilidae) parasitizing different species of fish from two environments in southern Brazil

The parasitic copepod Gauchergasilus euripedesi (Montú, 1980) Montú & Boxshall, 2002 was described from plankton samples and specimens found in four fish species from the estuarine area of Patos Lagoon, state of Rio Grande do Sul (RS), Brazil. Later, one different fish species was reported parasitized with G. euripedesi in the same locality. Species of Astyanax Baird & Girard, 1854 (Astyanax henseli Melo & Buckup, 2006 and Astyanax lacustris (Lütken, 1875)) and Psalidodon Eigenmann, 1911 (Psalidodon eigenmanniorum (Cope, 1894) and Psalidodon aff. fasciatus (Cuvier, 1819)) were collected in two environments (Pintada Island, municipality of Porto Alegre and Itapeva Lagoon, municipality of Terra de Areia, RS) to investigate their parasites. The copepods found in the gill arches were counted, processed, mounted in permanent slides, and photographed using light microscopy, or processed for observation in scanning electron microscopy. Specimens of P. eigenmanniorum from Pintada Island, A. lacustris and P. aff. fasciatus from Itapeva Lagoon, were parasitized by G. euripedesi, with prevalences of 29.03% (A. lacustris), 10.34% (P. eigenmanniorum), and 9.68% (P. aff. fasciatus). Measurements obtained for specimens of G. euripedesi were similar to those found in the literature, except for egg sacs which were larger in the specimens examined in the present study. In addition to being the first report of G. euripedesi parasitizing species of fish (A. lacustris, P. eigenmanniorum, and P. aff. fasciatus), the results presented here also extend the known geographic distribution of the copepod species.

Acusicola margulisae n. sp. (Copepoda: Ergasilidae) from freshwater fishes in a Nicaraguan crater lake based on morphological and molecular evidence

The ergasilid copepod Acusicola margulisae n. sp. is described based on material from three species of cichlid, Amphilophus citrinellus (Günther), Parachromis managuensis (Günther), and Oreochromis sp., and from the poecilid Poecilia mexicana (Steindachner), in the crater Lake Asososca León, Nicaragua. This constitutes the 15th species described in the genus Acusicola Cressey, 1970. The new species differs from all its congeners by the relatively longer first endopodal segment of leg 1, and the size and number of setae on second endopodal segment of leg 1. We provide the first gene sequence for a species of Acusicola. To examine the intraspecific genetic variation of the new species collected from different host species, sequences of the mitochondrial barcode region cox1 were generated. In addition, partial regions of the 18S and 28S ribosomal RNA genes were sequenced and used to infer the phylogenetic relationships of the genus Acusicola within the family Ergasilidae Burmeister, 1835. The phylogenetic trees yielded the isolates of Acusicola margulisae n. sp. as a reciprocally monophyletic lineage, and as the sister taxa of five genera of ergasilid copepods. The genus Ergasilus von Nordmann, 1832 was recovered as a paraphyletic group. These analyses indicate that phylogenetic relationships are not yet well resolved and more representative species and genera of the family are required to provide a robust classification of this highly diverse group of copepods.

Gauchergasilus, a new genus for Ergasilus euripedesi Montú, 1980, an abundant parasitic copepod from the Patos Lagoon in southern Brazil

Ergasilus euripedesi is redescribed from newly collected material of both sexes. A new genus, Gauchergasilus, is proposed, with Gauchergasilus euripedesi n. comb., formerly Ergasilus euripedsi Montú, 1980, as its type and only species. The new genus is characterised principally by the five-segmented antennule, the presence of a conspicuous barb on the concave margin of the claw of the antenna, the two-segmented endopod of leg 1 and the reduced fifth leg comprising two setae, one papillate. The male lacks the barb on the antennal claw but its other appendages are similar to those of the female, except for the maxilliped which is absent in females. The affinities of the new genus lie with the Acusicola group of genera.