[Morphological criteria of the species in cercaria of the genus Diplostomum (Trematoda: Diplostomidae) and methods for their study].

Taxonomy values of morphological features used for differential diagnostics of different taxa is considered for cercariae of the genus Diplostomum. It was shown that, as a rule, taxa criteria of superspecies ranks had a qualitative nature and were easily detected in live cercaria studies. In contrast, cercariae species diagnostics (CSD) is based exclusively on less significant, from a taxonomy point of view, quantitative features presenting absolute and relative body dimensions and that of cercariae organs as well as peculiarities of their cuticular armament. All this compels a taxonomist to use for CSD a whole range of diagnostic features of groups mentioned and increase their taxonomy values owing to standardization of cercariae collection, fixation and subsequent processing techniques, as well as broader application of variation-statistic methods of analysis that is possible only in cercariae studies through a use of permanent slices. A complex of methodical devices, which observance will ensure reliable CSD of the genus mentioned, is proposed. It encompasses cercariae collection and fixation as well as mounting of permanent balsame slides with preceding cercariae treatment with acetic-acid carmine (morphometric analysis), acid fuxine Sekki (cuticular armament staining) and silver nitrate (sensory apparatus detection). The reagents mentioned may form a real base for a creation of cercariae museum collections being not inferior in scientific value to existing trematode maritae and metacercariae stocks.