Estudo morfológico e biológico de tripanossomas de peixes do Brasil: caracterização in vivo e in vitro

Abstract

Parasites of the Trypanosoma genus have been described in a great number of fish species. Due to the pleomorphism presented by these protozoans and the rare specificity related to the vertebrate host, a lot of described species can have their validity questioned. Aiming to contribute with the knowledge about Brazilian fish trypanosomes, this study provides morphological and morphometric characterization of blood trypomastigotes from Hypostomus affinis and Hypostomus luetkeni collected in two sites of Minas Gerais state, along with their culture isolation and maintenance. The trypanosome infections were detected in 100% of H. affinis and 84,6% of H. luetkeni, showing a tendency of highest parasitemias on smaller hosts. The morphological analyses have allowed the distinction of four morphotypes, two of wich are possibly not related with any fish trypanosome species previously described in Brazil. The in vitro isolation of parasites was achieved in three biphasic media that were tested; however, their maintenance was possible only in the hyposmotic medium. The time required for the observation of first in vitro epimastigotes was different for each sampling site. The culture forms observed were spheromastigote-like, epimastigote and trypomastigote, and that latest two have showed a binary fission multiplication process. The multiplication sequence of cell organelles has followed the typical pattern of freshwater fish trypanosomes, with kinetoplast division starting before nucleus division, and also the salt water trypanosomes arrangement, with nucleus multiplication occurring previously to the kinetoplast. As result of the division process were generated two trypomastigotes, two epimastigotes, or one trypomastigote and one epimastigote. The trypanosomes isolates described here have showed in vitro features distinct from those of single trypanosome species isolated in Brazil, nominally: their physiological characteristics related to the medium growth and the division sequence of cell organelles. Altogether, these results can suggest that these trypanosomes could belong to different species; however, this hypothesis can only be confirmed by molecular analysis.