Oxyurid nematodes Aspiculuris tetraptera and Syphacia obvelata are both common mouse intestinal parasites; in the same location several species of trichomonads occur. Tritrichomonas muris is the most often found, but there are also some others: Tritrichomonas minuta, Pentatrichomonas hominis or Hexamastix muris. It is known that, under some circumstances, trichomonads can be found in the intestine of mouse pinworms, as reported by Theiler and Farber (1936) for T. muris in A. tetraptera and S. obvelata. What is interesting, trichomonads were found also in pinworms from trichomonad-negative mice. In 1933, Becker observed motile trophozoites of T. muris in the egg of S. obvelata. These observations offer a chance that the protist may be transmitted to a new host in similar manner (via pinworm eggs) as it was described for Histomonas meleagridis. In our study we document trichomonads in pinworm bodies, determine species of trichomonads, search for their localization, morphology and, based on the data, assess possibility of trichomonad transmission to a new mammalian host via pinworm eggs. By use of classical histology, in situ hybridization and transmission electron microscopy, we observed trichomonads exclusively in the intestinal lumen of both pinworm species. They were found in the entire pinworm...

Trichomonads (Parabasalia) are anaerobic microeukaryotes classified in the supergroup Excavata. Inclusion of parabasalids within Excavata is exclusively based on the molecular- phylogenetic evidence. Over 400 species of parabasalids have been described so far, and the vast majority of them are endobiotic. In contrast, only few species of free-living parabasalids forming four independent lineages have been described (Pseudotrichomonas keilini, Ditrichomonas honigbergii, Monotrichomonas carabina, Honigbergiella sp., Tetratrichomonas undula, and Lacusteria cypriaca). Lacusteria cypriaca is a new species and genus described in our recent paper. In this paper we published the first two sequences of SSU rDNA from Pseudotrichomonas keilini as well. All of these lineages are likely secondarily free-living, and they developed from endobiotic ancestors. In addition to the already published Lacusteria cypriaca and Pseudotrichomonas keilini strains, we have recently obtained seven another isolates of free-living trichomonads (LAGOS2D, E2NT, CK, LAGOS2M, GR8, GOU23 LIVADIAN, and VAV1A1); from all of these isolates we sequenced SSU rDNA and performed phylogenetic analyses. These isolates split into four independent evolutionary lineages, which indicate that free-living parabasalids are more diversed and...