White cat-sized shadows trail a polar bear stalking its prey. When the bear has eaten its fill, they dart in to devour the remains, carefully avoiding becoming the bear's dessert. Weighing only 6 to 11 pounds, these shadows are arctic foxes called Alopex (fox) lagopus (the hare-footed) for their fur-covered foot pads, resembling "bunny slippers," that insulate against frost when they dig the snow for lemmings - their favorite snack. Arctic foxes do not hibernate during the winter but depend upon their dense white winter coats for both camouflage and warmth against the -58oF cold. These winter pelts have the highest insulation value of any mammalian fur, and are highly prized by humans. Less important to humans is the fox's summer camouflage of gray to brown fur. An exception is the blue pelage maintained year-long by a mutant variety of arctic fox. These foxes reside in coastal habitats where their unique coloring provides a survival advantage they wouldnt enjoy on the winter tundra. Rare blue fur has a down-side for the foxes: it is highly coveted by humans. Many blue foxes are farmed for their pelts.
Related Record from CAplus
143: 472894 Two cysteine substitutions in the MC1R generate the blue variant of the arctic fox (Alopex lagopus) and prevent expression of the white winter coat. Vage, Dag Inge; Fuglei, Eva; Snipstad, Kristin; Beheim, Janne; Landsem, Veslemoy Malm; Klungland, Helge. Department of Animal and Aquacultural Sciences, Norwegian University of Life Sciences (UMB), Aas, Norway. Peptides 2005, 26(10), 1814-1817 (Eng). The authors have characterized two mutations in the MC1R gene of the blue variant of the arctic fox (Alopex lagopus) that both incorporate a novel cysteine residue into the receptor. A family study in farmed arctic foxes verified that the dominant expression of the blue color phenotype cosegregates completely with the allele harboring these two mutations. Addnl. to the altered pigment synthesis, the blue fox allele suppresses the seasonal change in coat color found in the native arctic fox. Consequently, these findings suggest that the MC1R/agouti regulatory system is involved in the seasonal changes of coat color found in arctic fox.
142: 212734 Circannual leptin and ghrelin levels of the blue fox (Alopex lagopus) in reference to seasonal rhythms of body mass, adiposity, and food intake. Mustonen, Anne-Mari; Pyykonen, Teija; Asikainen, Juha; Hanninen, Sari; Mononen, Jaakko; Nieminen, Petteri. Department of Biology, University of Joensuu, Joensuu, Finland. Journal of Experimental Zoology, Part A: Comparative Experimental Biology 2005, 303A(1), 26-36 (Eng). The aim of the study was to investigate the circannual rhythms of leptin and ghrelin in the blue fox, a variant of the endangered arctic fox, in relation to its seasonal cycles of body mass, adiposity and food intake. The effects of long-term fasting and exogenous melatonin treatment on these wt.-regulatory hormones were also investigated. The leptin concns. of the blue fox increased during the autumnal accumulation of fat and decreased during the wintertime and vernal wt. loss periods. The leptin levels peaked 2-6 wk before the max. values were obsd. for the body mass indexes, voluntary food intake, and body masses. The ghrelin concns. fluctuated widely during the autumn but decreased in the winter in assocn. with suppression of food intake. Exogenous melatonin advanced the seasonal changes in the food intake of the blue fox but did not affect the seasonal rhythms of leptin and ghrelin concns. The leptin concns. did not respond to the 3-wk fasting periods in a consistent way, but the ghrelin levels increased due to food deprivation. In addn. to the amt. of fat in the body the leptin secretion of the blue fox may be regulated also by other factors. The blue fox may also express seasonal changes in its leptin sensitivity. Our results reinforce the hypothesis that leptin does not function as an acute indicator of body adiposity in seasonal carnivores but rather as a long-term signal of nutritional status.
Related Structure from CAS REGISTRY
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L-Cysteine
CAS Registry Number: 52-90-4
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Updated: 1/26/2009 2:25:31 PM
