The Beringian Arctic pseudoscorpion is a charming Arachnid, living under rocks near sub-arctic rivers and streams, in primarily unglaciated parts of the Yukon. It has captured my fascinating for years, and the story of its natural history is starting to unfold. However, some fundamentals about the biology of Wyochernes asiaticus remain unknown: as the most northern pseudoscorpion in North America, how does it survive in such cold climates? How is it adapted to frequent flooding that occurs in its primary habitat, next to streams and rivers?
The Arctic pseudoscorpion, Wyochernes asiaticus
Science is a collaborative process, and I teamed up with two thermal biologists to start to answer some of these physiological questions. PhD student Susan Anthony and Prof. Brent Sinclair
*, both from Western University in Ontario, came to the Yukon with us last summer, and together we collected pseudoscorpions at Sheep Creek, just north of the Arctic Circle. Part of Susan’s PhD research is about the thermal biology of Arachnids, so Susan and Brent wanted to see what we could learn about Arctic pseudoscorpions. They brought the wee arachnids back to Ontario, and Susan ran a series of experiments, resulting in a recent publication (in Polar Biology)
Susan Anthony and Brent Sinclair, both from Western University.
The experiments may sound a little cruel, but they are the standard approach
when studying some of the cold tolerance, thermal biology and physiology of arthropods. Susan heated up and cooled down the critters, and discovered that they can survive up to about 38 degrees Celsius, and down to about -7 degrees Celsius. The upper threshold is relatively low compared to other arthropods, which makes sense since W. asiaticus
lives at high latitudes. Because the specimens didn’t survive freezing, we know it’s ‘freeze avoidant’ rather than ‘freeze tolerant’. This is aligns with what we know from many other northern (or southern! i.e, in the Antarctic
) arthropods. Presumably the pseudoscorpions adapt to the north by being able to supercool, or perhaps by cryoprotective dehydration,. However, its lower threshold isn’t that
low, given the extreme cold winter temperatures in the Yukon. But since our collections were in the mid-summer, this might mean it’s not yet started to adapt, physiologically, for the colder winter conditions.
The next experiments involved immersing the pseudoscorpions in water and seeing how long they survive. This was done because we were very curious to know how these tiny animals might live in habitats that flood frequently. Amazingly, 50 percent of the arachnids survived under water for up to 17 days (!), and after testing with de-oxygenated water, Susan had a similar result: they certainly weren’t relying on oxygen in the water for breathing. Susan did notice, however, that they appeared to have a silvery bubble or ‘film’ around their bodies when immersed so we assume they used this air bubble for breathing during the immersion period, something known from other arachnids.
Sheep Creek, Yukon – a habitat that frequently floods: now we know how the tiny Arachnids survive the flooding!
Putting this in the context of the pseudoscorpion’s habitat in the Yukon: it seems that the sub-arctic rivers in the Yukon typically flood for periods up to 10 days, in the spring. Our little arachnid likely just hunkers down in their habitats under rocks, breathing from air trapped around its body, waiting for floodwaters to recede.
I’m very excited about this paper, in part because of what we have learned that links the ecology of the species to its physiology. I’m also excited because this work represents a major advancement in the fundamental knowledge about Arachnids. Our work is the first to uncover any basic biology related to the physiological adaptations of pseudoscorpions to cold/heat and to immersion tolerance.
This is kind of stunning: the Pseudoscorpiones are an entire Order of Arachnids, yet nobody has ever worked to figure out how they adapt, physiologically, to extreme environmental conditions. AN ENTIRE ORDER! And it’s 2015! An analogy would be figuring out that some butterflies (Order Lepidoptera) bask in the sun, to thermoregulate. Or, like figuring out how ducks (Order: Anseriformes) don’t freeze their feet when standing on ice. These are ‘textbook’ examples of thermal biology and physiology – such facts could be considered common knowledge. Yet looking to the Arachnids, the story of the thermal biology of pseudoscorpions has only just begun. One paper at a time, we will continue to make progress.
The Arctic pseudoscorpion: it has stories to tell. Photo by C. Ernst, reproduced here with permission.
As Tschinkel & Wilson
state, every species has an epic tale to tell. Even tiny arachnids that live under rocks above the Arctic circle are proving interesting for many scientific disciplines: each chapter of its story is starting to unfold, and I’m quite sure there are a lot of very interesting chapters still to come.
Anthony, S.E., C.M. Buddle and B.J. Sinclair. 2015. Thermal biology and immersion tolerance of the Beringian pseudoscorpion Wyochernes asiaticus. Polar Biology.
*A sincere thanks to Brent and Susan for including me on this paper, and for being willing to come to the Yukon with our team, to do collaborative research. I’ve learned a great deal in the process, and am delighted that partnerships between ecologists and physiologists can work out so well.