13 Mar 2015

Jumping Jiminy! It's Snow Flea Season!

By Jan Thornhill
(Rolf Schlangenhaft)
Though there's still two feet of snow covering the forest floor, there are signs everywhere that spring is on its way. Chickadees have started singing their mating song! The warm sun is tatting lace into south-facing snowbanks! The driveway has turned to mud! And sunny depressions and ruts in the snow are liberally sprinkled with black pepper! But, wait a second...why would there be black pepper on the snow? And why is that black pepper JUMPING??
Close-up, tiny snow fleas have a blueish cast. 
The first time I found these leaping blackish blue dots in the snow, I had no clue what they were, so I called them snow fleas—which it turns out is what everybody else calls them, from Russia to Sweden to France— though they're not even remotely related to fleas. What they are is a very interesting type of springtail. 


Springtails are very cute little guys that, though they have six legs like insects, are nonetheless different enough that they're not included in that class: among other little quirks, they have fewer abdominal segments, lack proper compound eyes, and shed their exoskeletons throughout their lives. They also have a special way way of jumping. 
Sminthuridae sp. springtail (Tim Evison/Wikipedia)
Almost all springtails have a tail-like appendage on their abdomen called a furcula. This little device—the biggest springtails themselves are only 3mm long—is folded under the creature's belly and held there under tension by another structure called a retinaculum. When this click mechanism is triggered and the furcula snaps against whatever a springtail is sitting on—be it twig or fallen leaf or crust of snow—the tiny little guy is flung into the air. Kind of like the action of an old tin click toy. This makes it fun to poke your finger into a clutch of snow fleas, which makes them all trigger their devices at once. 

Remember these?

Sadly, springtails have no aiming ability, so they don't have much choice in the direction they go, but the quick random "boings" can be enough to keep them out of the mouths of predators.

Like most other springtails, snow fleas are mini garburators that help to make soil by eating decaying organic matter, algae, fungi and fungi spores, and poop—which is sometimes their own. Thousands can be rummaging though the moist forest floor litter at your feet, but are usually not noticed because they're so incredibly tiny.

When there's no snow, snow fleas can be found in forest litter.
No one knows exactly why snow fleas creep up through melting channels in snow to the surface on warm days at the end of winter, but the fact that these minute "cold-blooded" creatures are capable of such activity in cold temperatures when other over-wintering insects remain dormant has interested researchers for a long time. 

Thousands of snow fleas in tire ruts in snow... 
...or in crevices. (both photos Rolf Schlangenhaft)

A couple of these researchers, Laurie Graham and Peter Davies of Queen's University have isolated a protein from snow fleas that acts like antifreeze in their bodies. Though there are a number of different animals that have evolved proteins that protect their tissues against the nasty effects of freezing, including the woolly bear caterpillar and the grey tree frog, two characters featured in my recent book, Winter's Coming: A Story of Seasonal Change  about animals preparing for winter, the protein found in snow fleas, has a novel, and possibly very useful characteristic that other animal "antifreezes" don't have: at higher temperatures they break down. The exciting possibility is that this protein might be of use for organ transplants, which could not only be kept colder, and therefore stored longer than they can be now, but also, when the organ is finally used, the protein will be cleared from a patient's before harmful antibodies can form.  


Reference

Graham, L.A. and Davies, P.L. (2005) Glycine-rich antifreeze proteins from snow fleas. Science 310, 461.

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