|Arctic Woolly Bear, Baffin Island|
Gynaephora groenlandica (common name: Arctic Woolly Bear Moth) is a Lymantriid moth found within the Arctic circle, in Greenland and Canada. It is best known for its very slow rate of development. It was once estimated that it had a 14-year life cycle from egg to adult moth, a unique life cycle among the Lepidoptera with the ability to withstand temperatures below −60 °C. The larvae degrade their mitochondria in preparation for overwintering and re-synthesize them in the spring, and each instar of the caterpillar takes about a year. Subsequent studies have revised the life-cycle duration to 7 years.
The arctic woolly-bear caterpillars are unique in their combination of adaptations to the polar extremes. They spend nearly 90% of their life frozen and only about 5% feeding on the tundra during the month of June; the remainder is spent in summer aestivation within hibernacula (protective cocoons).
Hiding within hibernacula serves several functions: 1) protection from insect parasitoids that kill ca. 75% of the larvae and pupae, 2) avoidance of secondary metabolites built up in their food source, the arctic willow, 3) degradation of mitochondria linked to hypometabolism and antifreeze synthesis, 4) conservation of energy reserves needed to synthesize cryoprotective compounds required for freezing survival.
Two insect parasitoids (i.e. parasites that kill the host) attack woolly bear moth caterpillars: an ichneumonid wasp (reported as Hyposoter pectinatus but probably Hyposoter deichmanni) and a tachinid fly (Exorista thula). The wasp, a solitary parasitoid, kills about 20% of the 3rd and 4th instars of the host while the gregarious bristle fly causes ca. 50% mortality in the instar V, VI and pupae.
The extreme winter temperatures are not as detrimental to Gynaephora caterpillars as are the parasitoids. The larvae are extremely freeze tolerant, able to survive temperatures down to -70°C. As temperatures decrease during the late arctic summer the larvae start synthesizing cryoprotective compounds, such as glycerol, in addition to some unusual ones, e.g. betaine. Accumulation of these "antifreezes“ is aided by bottle-necking of oxidative phosphorylation through mitochondrial degradation. The woolly-bears re-synthesize the mitochondria the following spring upon resumption of their activity.
The specialized adaptations to environmental constraints adopted by arctic woolly bear moths and other cold-tolerant insects have been during the past 15 years used to develop new technologies for the preservation of cells and tissues.
In popular culture
The Natural History Unit of the BBC filmed arctic woolly bear moths in their natural habitat on Ellesmere Island during June 2009. The sequence became part of the BBC's sequel to Planet Earth called Frozen Planet, broadcast on BBC One in Autumn 2011 (with the US broadcast following on Discovery Channel in spring 2012).
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