Myxobolus spp. (Cnidaria: Myxobolidae) in the circulating blood of fishes from Goiás and Mato Grosso States, Brazil: case report

Abstract

Myxosporidiosis is an infectious disease caused by myxozoans of the Phylum Cnidaria, Class Myxosporea, and Order Bivalvulida, considered a common parasite in fresh and saltwater fishes that parasitize many organs, especially gills. In the present study, 49 specimens of fishes belonging to eight genera: Tetragonopterus, Leporinus, Myleus, Pirinampus, Rhapiodon, Pygocentrus, Ageneiosus, and Serrasalmus were collected and blood smears were made, fixed with absolute methanol, and stained with Giemsa 10% to survey hemoparasites. However, myxospores were found in the circulating blood of five (10.20%) fishes belonging to genus Tetragonopterus, Myleus, and Pygocentrus. Two morphological types of Myxobolus spp. were identified in all the five fish specimens analyzed. Usually, investigations on myxozoans in fish are carried out with the search for plasmodia or cysts in the fish organs and observation of the cavity of organs. Nevertheless, this study highlights the importance of also examining the blood of these animals, since these parasites can cause severe pathogenic diseases in fish. Thus, the blood analyses can proportionate preventive sanitary control for commercial fish avoiding economic loss.

Effect of 80% ethanol or 10% formalin fixation, freezing at −20 °C and staining on Myxobolus (Myxosporea) spores to be deposited in parasitological collections

“…The effect of these stains on the measurements of the spores in most cases were not studied, but some of these procedures have positive effects on the better knowledge of the structure of the spores or their location in the host. For example, Úngari et al (2021) stained spores carried by the blood stream with eosin methylene blue according to Giemsa (EMB) method, and Kato et al (2017) successfully detected the undeveloped polar tubules in the rudimentary polar capsules of M. paratoyamai using Diff-Quik stain.…”