Extremely high abundances of Prasiola crispa-associated micrometazoans in East Antarctica

To elucidate poorly known aspects of the microscopic metazoan distribution in ice-free parts of the Antarctic, we examined samples of the multicellular terrestrial alga Prasiola crispa, collected over the last decade in different parts of continental East Antarctica and Haswell Island. We found that the micrometazoans inhabiting the algae consist of remarkably abundant bdelloid rotifers (subclass Bdelloidea), followed by tardigrades. We did not find nematodes. The rotifer assemblages were characterized by low diversity (only six species). Nevertheless, rotifer densities were extremely high: mean densities ranged from 75 to 3030 individuals per 100 mg of the dry sample weight and the maximum value numbered in excess of 8000 per 100 mg of the dry sample weight. These data show that terrestrial algae, along with mosses, are a very attractive habitat for rotifers and tardigrades in the Antarctic. The statistical analysis showed a lack of correlations between rotifer and tardigrade densities and nutrients (N, C, P, K and Na). Our findings are consistent with the patchy distribution of terrestrial micrometazoans in the Antarctic that has previously been found.