X-Message-Number: 29026
Date: Fri, 26 Jan 2007 09:11:20 -0800 (PST)
From: 
Subject: those remarkable woollybear caterpillars

[The mechanisms responsible for the unique ability of this animal to
survive -70 C with no mortality are almost entirely unknown. However
one component of its ability to resist starvation appears to be due to
the elimination of most of its own mitochondria.]

J Comp Physiol [B]. 1989;158(6):661-71.
Cold-induced mitochondrial degradation and cryoprotectant synthesis in
freeze-tolerant arctic caterpillars.
Kukal O, Duman JG, Serianni AS.
Department of Biological Sciences, University of Notre Dame, Indiana 46556.
  The larvae of Gynaephora groenlandica, a long-lived moth endemic to the
high arctic, are perennially freeze-tolerant and able to increase their
freeze-tolerance by synthesizing glycerol. Cold-induced mitochondrial
changes were correlated (using electron microscopy, DNA staining,
cytochrome c assay, and oxygen uptake) with glycerol production (using NMR
spectroscopy) in larvae under different acclimations and in the
field. Hypometabolism in summer- or warm-acclimated larvae led to
glycerol accumulation. Extended exposure to near-zero or freezing
temperatures caused mitochondrial degradation and glycerol
accumulation. Rapid freezing of warm-acclimated larvae did not result in
mitochondrial breakdown. Mitochondrial reconstitution upon
warm-acclimation occurred much more rapidly (less than 1 week) than did
degradation (greater than 2 months). Concomitant with mitochondrial
breakdown was reduced oxidative metabolism, but the cytochrome c
concentration remained independent of acclimation temperature. The
adaptive response to cold by mitochondrial degradation and glycerol
accumulation by G. groenlandica may be linked to diapause in other
species of ectotherms.
PMID: 2715455

J Exp Biol. 1999 Jan;202(1):47-53.
Metabolic opportunists: feeding and temperature influence the rate and
pattern of respiration in the high arctic woollybear caterpillar
gynaephora groenlandica (Lymantriidae) Bennett VA, Kukal O, Lee RE.
Department of Zoology, Miami University, Oxford, OH 45056, USA and
Department of Biology, University of Victoria, Victoria, British
Columbia, Canada V8W 3P6.
  Arctic woollybear caterpillars, Gynaephora groenlandica, had the
capacity to rapidly and dramatically increase respiration rates up to
fourfold within 12-24 h of feeding and exhibited similar decreases in
respiration of 60-85 % in as little as 12 h of starvation. At the peak of
their feeding season, the respiration rates of caterpillars also increased
significantly with temperature from 0.5 to 22 degreesC for both fed and
starved caterpillars (Q10=1-5). Indicative of diapause, late season
caterpillars had depressed respiration rates which were less sensitive to
temperature changes (Q10 approximately 1.5), while respiration rates for
caterpillars that had spun hibernacula were even lower. G. groenlandica
did not appear to demonstrate metabolic cold adaptation compared with
other temperate lepidopteran larvae. The seasonal capacity to adjust
metabolic rate rapidly in response to food consumption and temperature
(which can be elevated by basking) may promote the efficient acquisition
of energy during the brief (1 month) summer growing and feeding season,
while conserving energy by entering diapause when conditions are less
favorable. These adaptations, along with their long 15-20 year life cycle
and the retention of freeze tolerance year-round, promote the survival of
G. groenlandica in this harsh polar environment.
PMID: 9841894


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