The Undead of Winter

 By Jan Thornhill

Ruby LOVES to "play dead" so we can will bury her in snow!

I love early spring! And no – I’m not talking about tulips and the return of migratory birds, though I have nothing against those things. I’m talking about earlier, in the first weeks of March, when there’s still plenty of snow on the ground, when, for all intents and purposes, it’s still the dead of winter.

Except it’s not dead.

Minute snow fleas appear on warm days in late winter.

In fact, there’s a surprising amount of life in the late winter forest here in Ontario – especially when the temperature squeaks a few degrees above the freezing mark. By early March, tree sap has begun to flow. Within a few days, deciduous crowns in the distance have taken on a haze, as if someone has smeared wet watercolour across the tips of their sharp branches. Their leaf buds are plumping. Male chickadees start using their “Hey, sweetie,” song, which, I think, is self-explanatory. Skunks wake from their winter torpor and amble about briefly – possibly just to stretch their legs – before returning to their dens to wait for real spring to come. On sun-warmed snow patches at the base of trees, snow fleas congregate, sometimes by the tens of thousands (see my post about snow fleas here).

This perennial Red-belted Polypore (Fomitopsis pinicola)
will drop spores on warm winter days.

And, all over the forest—believe it or not—fungi are procreating like crazy.

Amanita frostiana has a mycorrhizal relationship
with oaks and conifers.

These are not your basic ground mushrooms with caps and stems that you see in summer and fall. Most of those are mycorrhizal, and have a mutualistic relationship with trees, trading underground water and nutrients for the sugars that trees produce. But trees shut down sugar production in the late fall, so the underground networks of mycelia of mycorrhizal fungi also shut down during the frozen months.

The Violet-toothed polypore (Trichaptum biforme) is an annual saprobe.

But there are all kinds of other fungi that have a different kind of relationship to trees. They rot them. Many of these tree decayers, or saprobes, are polypores. Polypores develop their spores inside tiny tubes instead of on gills like store-bought mushrooms. 

The Hexagonal-pored Polypore (Neofavolus alveolaris)
 has—surprise!—hexagonal pores.

The most commonly noticed polypores are shelf fungi or conks. Many are perennial – they have skeletal hyphae—tissue than can withstand freezing and thawing—and just keep growing and growing, sometimes for 70 years or more. And during that time, whenever the temperature goes above freezing for a couple of days, these fungi produce spores. 

Yearly growth layers are obvious on this Phellinus that grows
new spore-producing tubes on its underside each year. 

But, why, you might wonder would they send out spores so much earlier than the birds start doing it and the bees start doing it—when the forest is still, in effect, asleep?

The Gilled Polypore, Lenzites betulina, has elongated tubes that almost look like gills.

They do it early because polypores, like all fungi, are opportunistic. Polypores that grow on living trees usually inhabit the heartwood that runs up the core of a tree trunk. To set up shop in this deadwood, a polypore has to get past a tree’s sapwood, the living layer below the tree’s bark. In the winter, deep freezes cause fractures in tree bark. These frost cracks are perfect for catching passing spores. When spring rains moisten the crevices, and before the tree has time to seal these cracks, the spores germinate and their mycelia work their way into the core. Once past the tree's defences, the fungus sets up shop, spreading its mycelia up and down and around. A fungus can secretly live inside a tree—gradually breaking down lignin and cellulose—for many years before it gives us humans a clue of its presence—by producing reproductive organs (shelf fungi, or conks) on the tree’s exterior.

Fomes fomentarius, is commonly called the Hoof Fungus
 (its shape)  or Tinder Fungus (used to carry fire from place to place
before matches were invented; Ötzi was carrying some).

The Cinnabar Polypore (Pycnoporus cinnabarinus) is the colour of dragon's blood!

The common name for Trametes versicolor is Turkey tails—for good reason

Chicken-of-the-Woods is an excellent edible polypore
 that has the unmistakable texture of overcooked
chicken if you miss its succulent stage.

This Artist's Conk (Ganoderma applanatum) is exhibiting geotropism
— the fungus first grew while the tree was still standing, then, after the tree 
fell, added new growth with its pore surface—once again—facing down.

Jumping Jiminy! It's Snow Flea Season!

By Jan Thornhill

Snow fleas look like hopping black specks in the snow (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.

Springtails 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. In the winter, snow fleas are eat spores that accumulate on the surface of melting snow.  

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.