A New Species of Gussevia (Monopisthocotyla: Dactylogyridae) Parasitizing the Gills of Astronotus Ocellatus (Cichliformes: Cichlidae) in the Caatinga Domain, Northeastern Brazil

PURPOSE: A new species of Gussevia Kohn et Paperna, 1964 (Monopisthocotyla, Dactylogyridae) is described based on specimens recovered from the gills of Astronotus ocellatus (Agassiz, 1831) (Cichliformes, Cichlidae) collected in the Ubaldinho weir, state of Ceará, Brazil. MATERIALS AND METHODS: Some obtained monopisthocotylans were mounted on slides using Gray and Wess medium and studied using an optical microscope with a phase-contrast. Illustrations were made using a drawing tube attached to a Leica DM750 microscope and vectorized using Inkscape 1.4 software. RESULTS: Gussevia lamarckii n. sp. is characterized by having an accessory piece nonarticulated with the MCO base, comprising two dorsal subunits, one Y-shaped and the other one rod-shaped; and an elongated peduncle. Furthermore, the new species can be easily distinguished from the other congeners by possessing (1) a ventral anchor with an external protuberance at the junction between the root and the shaft, and (2) a superficial groove at the base of the dorsal anchor. CONCLUSIONS: This study presents a new species of the genus Gussevia, the fourth described from Astronotus fish and the first from A. ocellatus and the aquatic ecosystems of the Caatinga domain.