Summary
Brasicystis bennetti n. gen., n. sp. (Trematoda: Digenea: Didymozoidae) is described from a commercially important Amazonian fish called the "pescada" (Plagioscion squamosissimus). This parasite lives in the subcutaneous tissues of the mouth and opercula, and also in oval cysts attached to the gills. The presence of these helminths under the skin in these locations causes visible yellow spots because of the accumulation of large numbers of eggs. The new form is the third species of Didymozoidae to be reported from freshwater in the world, and it is caracterized as having a laterally flattened hindbody with a ventral fold anteriorly, and a single tubular testis which extends posterior to the tubular ovary The trematodes have a total length of up to 19 mm. and very small eggs (8x15 µ).