Some ultrastructural data on the spore development in a Henneguya sp. parasite of the gill of a Brazilian fish.

A myxosporean Henneguya sp. was found in the gill filaments of a freshwater fish, Hoplosternum littorale, from the lower Amazon river near Belém, Brazil. Plasmodia were represented by numerous vegetative nuclei, generative cells and sporogony stages. The spore body was ellipsoidal and each valve presented a tapering tail approximately 45.2 microns in length. The spores differed from those of previously described species in their shape and size. The developmental stages are described and discussed. This histozoic species is reported to be pathogenic, inducing great mortality in the host.