Gastric nematode co-infections and redescription of Neoterranova serrata in Arapaima gigas from Central Amazon.

In the Amazon region, Arapaima gigas holds significant gastronomic and cultural value compared to other fish species due to its large size. This fish is home to various helminth species that parasitise primarily its gastrointestinal organs. During the 2023 dry season, a total of 60 gastrointestinal organs from A. gigas specimens were collected from a fisheries management program conducted by local residents within the Mamirauá Reserve. For gastric parasitological analysis, each organ was separated in containers, and the parasites were recovered, washed, and fixed in 70% alcohol for analysis by light and scanning electron microscopy. Additionally, stomach samples of the hosts infected with parasites were fixed in 10% formalin for histopathological examination. 16% of the parasitised fish presented ulcerative areas in the gastric mucosa of varying degrees. Microscopically, a severe inflammatory reaction with infiltration of eosinophils, lymphocytes, and macrophages was observed, associated with co-infection by Goezia spinulosa and Neoterranova serrata. Additionally, morphological and morphometric data aided by scanning electron microscopy for N. serrata were added.