Abstract
Asotana magnifica n. sp. (Isopoda, Cymothoidae) is described from the buccal cavities of
piranhas (Serrasalmus sp.) from the Territory of Roraima, Brazil. The species was based on two adult
females and an additional aberrant female was also studied. A table compares the new species with the
two species already known in this genus. Distinguishing characters of the new form are: the shape of
the body, which narrows abruptly at the abdomen; the pereonite 2 without tubercles; the merus of
pereopod 7 with two bosses and the antenna of 5 segments. These isopods are not pathogenic and it is
thought that they feed on already digested material regurgitated periodically by the host. It is suggested
that for this reason, and in spite of their large size, they might be commensals rather than parasites.
This is the third report of this genus and the first for Brazil.
