ИСТИНА

Tantulocaridans are minute parasitic crustaceans with curious development and complicated life cycle. They were established as a separate class in 1983 (Boxshall, Lincoln, 1983), but their phylogenetic position within Crustacea is still doubtful. Their morphological characters are insufficient for detailed comparison with other crustaceans and make difficult to determine the tantulocaridan position on the arthropod phylogenetic tree. According to some morphological traits they are believed to be close relatives of Thecostraca. However, no molecular analysis of their phylogeny has been conducted. Complete 18S rDNA sequences of two species of Tantulocarida (Arcticotantulus pertzovi, Microdajus tchesunovi) were obtained for the first time. Bayesian analysis shows that affinities of Tantulocarida lie within Thecostraca, where they are resolved as a sister group of Cirripedia. This relation could be proved by at least one probable synapomorphy: cement adhesion of last larval instars is unique for both groups, further synapomorphires may come from morphology of tantulocaridan and cirripede nauplii. Our results prove close affinities of Tantulocarida and Thecostraca, however further analysis of other genetic markers is necessary.