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

Abstract

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. Supplementary Information The online version contains supplementary material available at 10.1007/s11230-022-10076-y.

Acusicola rochai n. sp. (Copepoda: Ergasilidae) parasitizing Anableps anableps (Anablepidae) from the Amazon Coast, with a key for Acusicola spp.

“…Additionally, there is only an additional species of Acusicola that has dorsal protrusions on the pedigerous somites as in the new species, i.e. Acusicola iamarinoi Couto, Pereira, Luque, Paschoal & Pereira, 2022. Nevertheless, A. rochai n. sp.…”

“…Representatives of Ergasilidae are characterized by the second antenna modified in a robust prehensile organ, mandibles with two or three spinulate blades, lack of maxilliped in adult females, and leg 4 with one or two segments, or rarely absent (Boxshall and Halsey, 2004). Among the 30 genera hitherto described in the family, Acusicola can be identified based on a five-segmented antennule, a groove on the second endopodal segment of the antennae that latches the claw of the opposite side, allowing a complete encircling of the gill filament, and leg 1 with two-segmented endopod armed with at least six elements (and rarely three) (Amado and Rocha, 1996; Boxshall and Halsey, 2004; Couto et al ., 2023; Walter and Boxshall, 2024). Therefore, the present parasitic copepods have all the characters previously mentioned, clearly justifying their allocation in Ergasilidae and Acusicola .…”

“…Amado and Rocha (1996) relied primarily on the armature and proportion of leg elements of the ten known species at that time. Subsequently, eight additional species have been described, and new morphological traits have been documented in the genus, highlighting the necessity of updating this important taxonomic tool (Couto et al, 2023;Walter and Boxshall, 2024). Recently, Couto et al (2024b) observed that mounting copepods in permanent slides can compress and distort body shape.…”

“…Ergasilidae Burmeister, 1835 is a group of cosmopolitan parasitic crustaceans, commonly found on the gills, nostrils, fins, tegument and urinary bladder of fish, and rarely elasmobranchs and bivalve molluscs (Malta, 1993; Boxshall and Halsey, 2004; Couto et al ., 2023). This family is one of the most species rich within cyclopoid copepods, with 275 species from 30 genera currently known.…”

“…The genus Acusicola Cressey, 1970 was originally proposed to allocate Acusicola cunula Cressey, 1970, from the Needlefish Pseudotylosurus angusticeps (Günther, 1866) (Actinopterygii: Belonidae) in Brazil, and Acusicola tenax (Roberts, 1965), a parasite of the White crappie Pomoxis annularis Rafinesque, 1818 (Actinopterygii: Centrarchidae) collected in the USA, which was first assigned to Ergasilus . Currently, Acusicola comprises 17 species in which ten were reported from Brazil, mainly in the Amazon River Basin (Cressey and Collette, 1970; Couto et al ., 2023). This taxon belongs to a group of three genera within Ergasilidae that share a five-segmented antennule, and a latching mechanism on its antennae, which allow the copepod to completely encircle the gill filament of its host.…”