Abstract This study investigated the spatial distribution, parasite interactions, and affinities of Branchiura parasites according to macrohabitat and surface type on fish from the Araguari River, Amapá State, in the Brazilian Amazon. This study presents novel information on the interactions of branchiuran species with host fish, and how the morphology of their attachment structures is associated with different host surface morphologies, with and without scales. A total of 558 fish specimens of 26 species were collected, of which 109 fish (10 species) were parasitized by at least one branchiuran parasite; these were selected for further study. The parasites were collected from the buccal cavity, gills, fins, and integument of the host fish. Parasites with suction discs (Argulus) were mainly associated to hosts with small scales and no scales, while parasites with hooks (Dolops) were mainly associated to hosts with large scales. Overall, parasites with suction discs were more specialized per site than those with hooks. distribution River State Amazon morphologies 55 2 10 (1 cavity gills fins Argulus (Argulus Dolops (Dolops Overall 5 1 (

Abstract The aim of the present study was to investigate the infracommunities of ectoparasitic crustaceans in Phractocephalus hemioliopterus Bloch and Schneider, 1801, a catfish from the lower Amazon River, in the state of Pará, eastern Amazon region, Brazil. From 12 hosts examined, a total of 45 specimens of crustacean ectoparasites from 5 species were found in the tegument, oral cavity or dorsal fins. The species were: Argulus multicolor, Argulus violaceus, Dolops nana, Dolops discoidalis, and Braga patagonica. Dolops discoidalis was the dominant ectoparasite, while D. nana had the highest mean intensity in the tegument, which was the most infested host site. This is the first record of A. multicolor, A. violaceus, D. nana and B. patagonica parasiting P. hemioliopterus.

Resumen El objetivo del presente estudio fue investigar las infracomunidades de crustáceos ectoparásitos en Phractocephalus hemioliopterus Bloch y Schneider, 1801, un bagre de la parte baja del río Amazonas, en el estado de Pará, en la Amazonía oriental, Brasil. A partir de 12 hospederos examinados, se encontraron un total de 45 ejemplares de crustáceos ectoparásitos de 5 especies en el tegumento, cavidad o aletas dorsales orales. Las especies fueron: Argulus multicolor, Argulus violaceus, Dolops nana, Dolops discoidalis y Braga patagonica. Dolops discoidalis fue el ectoparásito dominante, mientras que D. nana tuvo la intensidad media más alta en el tegumento, que fue el sitio más infestado. Este es el primer registro de A. multicolor, A. violaceus, D. nana y B. patagonica parasitando P. hemioliopterus.