Here isn’t much competition in the cold winter for inverterbrates
As a child I have never been one of those kids frolicking around in the snow and enjoying winter sports. I’ve always been a lousy skier and never took to ice-skating. But as an adult I found nothing more enchanting than the serene atmosphere and ice-cold beauty of a northern Finland forest in winter. It clears your mind; it makes you appreciate you are alive and exist. I love the Finnish winter, which is perhaps surprising, because I also like insects, but they and other invertebrates are not at all common in, on, or under the snow – and that, of course, is not surprising since they largely depend on the warming rays of the sun to activate their metabolism, muscles, and senses. There are a few species, however, that have become adapted to the snowy habitat and cannot be found anywhere else.
The Rocky Mountain iceworm, just like some Icelandic rotifers, is an inhabitant of glaciers and snowfields. It finds pollen and algae in the thin film of liquid water on the ice-crust. As chilly night temperatures begin to freeze the surface, the iceworm, an annelid related to earthworms (only considerably shorter) retreats to safer depths beneath the frozen crust. In northern Europe glass-snails of the genus Vitrina with their small transparent shells can often be seen in spring under thawing ice sheets, laying their eggs. The snowfly Chionea, (actually a tipulid crane fly and despite lacking wings a real fly) occurs in the same but even snowier habitat as Vitrina and has larvae that feed on rotting leaves in and under the snow.
The wingless Alpine scorpionfly Boreus is quite large for a snow insect and it may be seen hopping about on the snow surface in search of pieces of moss or dead glacier fleas (it is not a fussy eater when it comes to food). Glacier fleas are actually not fleas at all, but tiny 1.5 mm long, primitive, wingless springtails of all snowy mountains in the world. They can occur in such astronomical numbers that the snowfields from a distance may look brown or reddish. Springtails of a darker and rather greyish coloration are present in Antarctica and are sometimes blown by the wind into crevices or corners where I was once able to collect handfuls of them. I later used some of that catch for an electron microscopic study of their eyes, because it seemed interesting to find out how they’d cope under the Antarctic 24 hour summer daylight conditions and avoided snow blindness due to the light’s high UV-content.
Far rarer than the tiny snow springtails is the entomologist’s marvel: the Grylloblatta. Representing an entire order within the classification of insects, grylloblattids are all cold-loving, long lived insects that come out at night and are known from only a few places on Earth (Mt. St Helens is one; mountains in Japan to which Prof. N. Gokan took me, another). Although not as cold-tolerant as the snowfly, which still runs around at -10°C, grylloblattids survive injury and frozen limbs. They share this ability to survive freezing with other insects like chironomid larvae, New Zealand alpine wetas etc. (which, however, only survive due to anti-freeze in their bodies or freeze-tolerant tissues and are not active at sub zero temperatures). Grylloblattids are in no hurry to reach sexual maturity and may take 8 or more years. Maybe because of a chronic shortage of food in “grylloblattid territory” females have been reported to eat their males. Whatever may have driven the snow invertebrates to seek a living in their chilly environment, ice ages have come and gone, but they have had little effect on our snow-hardy invertebrates. Life in the freezer, after all, has its advantages.
© Dr V.B. Meyer-Rochow and http://www.bioforthebiobuff.wordpress.com, 2018.
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