Braga nasuta (Cymothoidae): an ectoparasite of the Giant Amazonian fish Arapaima gigas (Osteoglossidae) fingerlings cultured in the Amazon region in Northern Brazil

Abstract

Isopods Cymothoidae are organisms that parasitize several fish species, both marine and freshwater, provoking important physiological alterations and secondary infections. The genus Braga was proposed to harbor three species of parasitic isopods in freshwater fish from South America: B. brasiliensis, B. cichlae and B. nasuta. Posteriorly, other four species were included: B. patagonica, B. amapaensis, B. fluviatilis and B. bachmanni. Regarding the geographical distribution of the genus, there are registers in Brazil, Argentina, Suriname and Paraguay. In this study, 3,625 fingerlings of pirarucu Arapaima gigas were examined from a commercial fish farm in the Amazon region, Pará State, to observe and identify possible parasites. A total of eleven ectoparasitic isopods were carefully removed from the body surface of the hosts and fixed in alcohol 70%. They were processed and identified as Braga nasuta. Parasitological indexes were prevalence of 0.303%, mean intensity of 1.000±0.000 and mean abundance of 0.003±0.055. This is the first report of B. nasuta in pirarucu fingerlings.