A new species of Dactylobiotus (Parachela, Eutardigrada) from King George Island, Antarctica

Abstract

Background: Limno-terrestrial tardigrades form one of the most dominant groups in the scanty terrestrial freshwater ecosystem of Antarctica. However, due to their limited key morphological characters and restricted access to the habitats, taxonomic study on Antarctic tardigrades largely remains to be challenged. KOPRI (Korea Polar Research Institute) ecology team collected several species of tardigrades near the King Sejong Station, King George Island, Antarctica during 2014-2015 seasons. Results: Among the collected freshwater tardigrades, one group shows a buccal-pharyngeal apparatus with ten peribuccal lamellae, and a cuticular connection which joins two claws in each limb. These characters warrant a generic assignment to Dactylobiotus. The new species is quite large in size (600-700 μm) with prominent eyespots and smooth cuticle. The egg has circular or slightly hexagonal cone-type processes with a tip. Compared to D. ambiguus and D. caldarellai which have a rather similar morphology, the new species shows claws with longer primary branch at all limbs. The 18S, 28S rDNA and cytochrome c oxidase subunit 1 (CO1) sequences do not correspond to any previously-reported sequence, although only limited molecular data of tardigrades have been reported so far. Conclusions: Based on the pt-ratio (the ratio of the length of a given structure to the length of the buccal tube) of the buccal-pharyngeal apparatus and claws, the morphology of eggs, and the DNA sequences of three partial genes, this species is considered as a new species of Dactylobiotus.