The discovery of the tardigrade, Milnesium sp., in the McMurdo Dry Valleys, Antarctica, and the potential implication for biotic interactions

Poster Disciplines/Format:
Poster Number: 
Presenter/Primary Author: 
Uffe N. Nielsen
Diana H. Wall
Byron J. Adams
Jeremy Whiting
Scott Peat

The McMurdo Dry Valleys, Antarctica, are a cold desert and represent one of the most inhospitable environments on earth. As a consequence the food webs are simple compared to most other terrestrial ecosystems, and limited to microbes and the nematode Scottnema lindsayae in dry areas, which includes most of the landscape. However, the few wet areas represent hotspots for soil organisms and support a greater diversity of soil fauna, often including the nematode genera Plectus and Eudorylaimus, and a few species of rotifers and tardigrades. Despite the greater diversity the food webs are still simple, and no predators have been observed in these food webs. The full extent of rotifer and tardigrade diversity is however not well known. During the austral summer 2008-09 we used a systematic approach to estimate the species richness of tardigrades, and discovered two previously unrecorded species in the McMurdo Dry Valleys. One of the species we found belonged to the genus Milnesium. This genus is considered cosmopolitan, and has been recorded on the Antarctic Peninsula, but these are the first individuals found in the Dry Valleys. Some of the species belonging to this genus, including the type species Milnesium tardigradum Doyére, are considered to be exclusively predatory, and our observations of live specimens from the Dry Valleys indicated that these are also predatory. Hence, this is the first evidence that the food webs in the Dry Valleys include a tardigrade species that could function as ‘top-predator’ in the biotic hotspots, and its presence suggests that there is a potential for greater biotic interaction within the soil food webs than previously hypothesized. Whether the specimens of Milnesium sp. represent a new species is currently being scrutinized using images taken with a scanning electron microscope, high resolution microscopy and DNA.