Bdelloid rotifers (Bdelloidea, Rotifera) in shallow freshwater ecosystems of Thala Hills, East Antarctica

Abstract

AbstractShallow waters, little-studied in Continental Antarctica, among other micrometazoans host bdelloid rotifers, which diversity, ecology, and distributional patterns in turn are poorly known. To address these issues, we analysed plankton samples collected during the 2018/2019 season in the Thala Hills oasis (East Antarctica), in shallow freshwater lakes and temporary ponds that formed during intense snow melting in December–January. Bdelloids were present in more than 90% of the sites with nine species revealed. The most frequent were Antarctic endemics [Philodina gregaria (P. gregaria), Adineta grandis (A. grandis), and Adineta coatsi (A. coatsi)], while some non-abundant bdelloids either provide characteristics of widely distributed taxa or require further taxonomy studies as they can be species new for the science. The abundance of bdelloids varied greatly across studied sites and localities, with a maximum of more than 700,000 ind m−3 and an increasing tendency to be more numerous in rock-basin temporary ponds, compared to larger lakes, with variability for different taxa. The environmental parameters strongly explain the bdelloid distribution (78.4% of the variation), with the most important factors being the type of bottom (9.9%), altitude (8.0%), TDS (6.6%), and salinity (6.5%). The cyanobacterial mats from the bottom didn’t contribute much to bdelloid distributional patterns, despite being known to be a preferred habitat for micrometazoans including rotifers. These results shape a perspective to study the processes of the formation of Antarctic seasonal aquatic habitats settled by organisms, which demonstrate an ecomorphological range from planktonic organisms to crawling ‘scrapers’.