PROTOZOOLOGY - 059 - HIGH GENETIC HETEROGENEITY OF SYMBIONT-HARBORING TRYPANOSOMATIDS

Symbiont-harboring trypanosomatids (SHT) have a undefined morphology, except Blastocrithidia culicis, whose typical undulating membrane is diagnostic of the genus. SHT are choanomastigote-like flagellates, which, in their life cycles, present forms with post-nuclear kinetoplast as initially reported by Souza and Côrte-Real (Rev. Inst. Med. Trop. S.P.,1991) and recently named ophistomorphs by Teixeira et al. (J. Protozool., in press). There are only 4 species in this group: C. oncopelti, C. deanei, C. desouzai and H. roitmani.

In order to identify new SHT, we first confirmed that all available species could be grown in a medium without hemin and then proceeded to examine 37 trypanosomatids from insects and plants for the ability to grow in this medium. Among those, only the isolate TCC/USP-263 could be grown in absence of hemin. This isolate presents opisthomorphs and the same unconspicious morphology of the SHT. Under EM it also proved to bear a bacterial endosymbiont.

Du & Chang (Mol. Biochem. Parasitol., 1994) reported that, although quite distinct from other trypanosomatids, C. deanei, C. oncopelti and C. desouzai presented SSU rDNA sequences practically identical. In contrast, restriction analysis of SSU rDNA (Camargo et al., 1992) and analysis of mini-exon gene (Fernandes et al., Mem. Inst. O. Cruz, 1995) detected marked differences among these flagellates.

We have comparatively analyzed several species of Crithidia, Herpetomonas, Phytomonas and Leptomonas and the 4 SHT plus the new isolate TCC/USP-263. The following parameters were analyzed: l) enzymes of the ornithine-arginine metabolism; 2) sizes of kDNA minicircles; 3) restriction maps of the rDNA SSU; 4) fingerprints of the SSU and LSU of rDNA; 5) ribosomal ITS analysis after PCR-amplification; 6) RAPD. By any and all of these parameters the flagellates with symbionts were found to differ from the trypanosomatid species examined as well as from each other. Actually, by any criteria, except for the presence of symbionts and opistomorphs, they are entirely distinct from each other. The degree of heterogeneity exhibited by SHT (concerning some traits that trypanosomatids of the same genus usually have in common) suggests that SHT do not constitute a homogeneous or monophyletic group.