Abstract
BackgroundAmphibian trypanosomes were the first ever described trypanosomatids. Nevertheless, their taxonomy remains entangled because of pleomorphism and high prevalence of mixed infections. Despite the fact that the first species in this group were described in Europe, virtually none of the trypanosomes from European anurans was analyzed using modern molecular methods.MethodsIn this study, we explored the diversity and phylogeny of trypanosomes in true frogs from Europe using light microscopy and molecular methods.ResultsA comparison of observed morphotypes with previous descriptions allowed us to reliably identify three Trypanosoma spp., whereas the remaining two strains were considered to represent novel taxa. In all cases, more than one morphotype per blood sample was observed, indicating mixed infections. One hundred and thirty obtained 18S rRNA gene sequences were unambiguously subdivided into five groups, correspondent to the previously recognized or novel taxa of anuran trypanosomes.ConclusionsIn this work we studied European frog trypanosomes. Even with a relatively moderate number of isolates, we were able to find not only three well-known species, but also two apparently new ones. We revealed that previous assignments of multiple isolates from distant geographical localities to one species based on superficial resemblance were unjustified. Our work also demonstrated a high prevalence of mixed trypanosome infections in frogs and proposed a plausible scenario of evolution of the genus Trypanosoma.
Highlights
Amphibian trypanosomes were the first ever described trypanosomatids
The first three species of trypanosomes were described from frogs: the type-species Trypanosoma rotatorium (Mayer, 1843) Laveran, 1901, as well as T. loricatum (Mayer, 1843) Dutton, Todd & Tobey, 1907, and T. ranarum (Lankester, 1871) Danilewsky, 1885
Trypanosoma rotatorium was considered as an amoeba (Amoeba rotatoria), whereas T. loricatum and T. ranarum as ciliates (Paramecium loricatum and Undulina ranarum, respectively) [9, 10]
Summary
Amphibian trypanosomes were the first ever described trypanosomatids. their taxonomy remains entangled because of pleomorphism and high prevalence of mixed infections. The early discovery of these trypanosomes was facilitated by their large size and, better visibility under the light microscope This is the only group within the Spodareva et al Parasites & Vectors (2018) 11:447 genus Trypanosoma demonstrating remarkable morphological plasticity. The name T. rotatorium was the most popular one, as flagellates from about 60 species of anurans from Europe, Asia, Africa, as well as North and South America have been recorded under this name [14,15,16] All these reasons, along with rather limited efforts put in studying of amphibian trypanosomes, resulted in a relatively low number of species (about 60 in total) described by morphology. This number did not change significantly even after the advent of molecular phylogenetics
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