Molecular characterization of European Pygorchis Looss, 1899

Adult trematodes of the genus Pygorchis Looss, 1899 (Trematoda: Philophthalmidae) parasitize the cloaca of birds. The genus contains three species, all of which are rarely reported and molecular phylogenetics of which have not been applied. The absence of reference DNA sequences limit studies of their indistinct larval forms. Based on the materials that were obtained from birds of the Czech origin, we performed a molecular characterization of both currently known Pygorchis spp., which are known from the Palearctic, the type species Pygorchis affixus Looss, 1899 and Pygorchis alakolensis Zhatkanbaeva, 1967, and provided morphological description of the examined P. alakolensis specimen. We found that the two species were of similar dimensions; the only difference was in the position of testes and in the extent of vitelline follicles. However, the position of testes in P. affixus was variable, and approximately 10% of examined P. affixus individuals had testes positioned obliquely. The second feature that allows differential diagnostic, the extent of vitelline follicles, was more reproducible as the vitelline follicles of P. affixus did not extend beyond the intestinal caeca, or, in exceptional cases, they extended them at only one side. In the examined P. alakolensis individual, the testes were positioned obliquely, and the vitelline follicles extended beyond the intestinal caeca. We reported P. alakolensis for the first time from Europe; previously, it was known only from Central Asian lakes and rivers. We confirmed the classification of Pygorchis into Philophtalmidae.