Morphology and ultrastructure of definitive males of Arcticotantulus pertzovi and Microdajus tchesunovi (Crustacea: Tantulocarida)

Free-swimming definitive males of two species of Tantulocarida (Crustacea), Arcticotantulus pertzovi (Basipodellidae) and Microdajus tchesunovi (Microdajidae), were reared for the first time. Their morphology and ultrastructure were studied using scanning electron and light microscopy. A detailed analysis of the morphological characters of all currently described species revealed several features typical for most known male tantulocaridans, such as the presence of eight aesthetascs, seven pairs of multifid sensilla on the carapace, paired brush setae on the protopods of the thoracopods, and three furcal setae. The monophyly of the families Microdajidae and Doryphallophoridae is corroborated, while the families Deoterthridae and Basipodellidae are more likely paraphyletic.