Thermal biology and immersion tolerance of the Beringian pseudoscorpion Wyochernes asiaticus
Wyochernes asiaticus (Arachnida: Pseudoscorpiones: Chernetidae) is a pseudoscorpion distributed across Beringia, the areas of Yukon, Alaska and Siberia that remained unglaciated at the last glacial maximum. Along with low temperatures, its streamside habitat suggests that submergence during flood events is an important physiological challenge for this species. We collected W. asiaticus in midsummer from 66.8°N Yukon Territory, Canada, and measured thermal and immersion tolerance. Wyochernes asiaticus is freeze-avoidant, with a mean supercooling point of −6.9 °C. It remains active at low temperatures (mean critical thermal minimum, CTmin, is −3.6 °C) and has a critical thermal maximum (CTmax) of 37.8 °C, which is lower than other arachnids and consistent with its restriction to high latitudes. Fifty per cent of W. asiaticus individuals survived immersion in oxygen-depleted water for 17 days, suggesting that this species has high tolerance to immersion during flooding events. To our knowledge, these are the first data on the environmental physiology of any pseudoscorpion and a new addition to our understanding of the biology of polar microarthropods.
KeywordsPseudoscorpion Microarthropod Cold tolerance Critical thermal limits Immersion
Thanks to Mhairi McFarlane, Shaun Turney and Anne-Sophie Caron for assistance in the field. Chris, Beatrix and April Howard provided logistical support. Two anonymous referees provided comments that improved the manuscript. This research was supported by the Natural Sciences and Engineering Research Council of Canada via Discovery Grants to BJS and CMB and a Northern Supplement to CMB, and by a Northern Scientific Training Programme grant to SEA. Collections were made under Yukon Science and Exploration Permit 15-10S&E.
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