Callitetrarhynchus gracilis (Rudolphi, 1819) Pintner, 1931 (Cestoda: Trypanorhyncha) parasitizing the musculature of Sardinella brasiliensis (Steindachner, 1879) (Actinopterygii) off the coast of the state of Rio de Janeiro, Brazil.

Cestodes of the order Trypanorhyncha can frequently be found infecting the muscles of several marine fish species, and lead to a repugnant aspect of the fish and rejection by consumers. The Brazilian sardinella, Sardinella brasiliensis, occurs from the Gulf of Mexico and the Caribbean to northern Uruguay. In southeastern Brazil, fishing for the species is very intensive since it generates significant revenue as one of the most commonly consumed fish and an important element of the canned fish industry.