Hormones and metabolites of arctic foxes (Alopex lagopus) in response to season, starvation and re-feeding

Abstract

Svalbard's arctic foxes experience large seasonal variations in light, temperature and food supply throughout the year, which may result in periods of starvation. The aim of this work is to investigate if there are seasonal variations in post-absorptive plasma thyroid hormones (free thyroxin (fT 4 ), free triiodothyronine (fT 3 ) and reverse triiodothyronine (rT 3 )) and metabolites (free fatty-acids (FFA) and b-hydroxybutyrate (b-OHB)) with season and their response to starvation and re-feeding. The concentrations of post-absorptive free triiodothyronine were significantly higher in November than May, while those of thyroxin, reverse triiodothyronine, free fatty-acids and b-hydroxybutyrate remained unchanged. Possible explanations for the seasonal variations in free triiodothyronine are discussed. There were no significant changes from post-absorptive concentrations of thyroxin and reverse triiodothyronine in starved and re-fed foxes. However, free triiodothyronine concentrations decreased during starvation and increased again with re-feeding both in May and November. Starvation induced high levels of free fatty acids in both May and November, indicating increased lipolysis. There was a significant increase in b-hydroxybutyrate in November only, indicating that arctic foxes are capable of protein conservation during starvation.

Two cysteine substitutions in the MC1R generate the blue variant of the arctic fox (Alopex lagopus) and prevent expression of the white winter coat

“…In addition to the family study, blood samples were drawn from seven wild arctic foxes (of the white morph) that were caught near Ny-Ålesund (78 • 55 N, 11 • 56 E), Svalbard, Norway. These animals were a part of a larger project at the Norwegian Polar Institute, Tromsø, Norway [6,7]. Verification of the mutations found in the blue fox was also done in a blue fox originating from Finland.…”

Effects of season, food deprivation and re-feeding on leptin, ghrelin and growth hormone in arctic foxes ( Alopex lagopus ) on Svalbard, Norway

“…Generally, the plasma ghrelin concentrations were higher in May than in November (t-test, p<0.05). The plasma ghrelin concentrations were analysed against values of FFA concentrations of the same individuals from Fuglei et al (2000). The plasma ghrelin concentrations correlated negatively with the Fig.…”

“…Thereafter blood was sampled on day 7 and day 13 after food deprivation, and again on day 5 and day 9 of re-feeding, with the same protocol in May and in November. The arctic fox encounters long periods of food deprivation in winter in its natural habitat and is quite well adapted to withstand periods of food deprivation (Fuglei and Øritsland 1999;Fuglei 2000;Fuglei et al 2000;Nieminen et al 2001). The blood samples were obtained from the cephalic vein using a syringe (needle 1.2·40 mm); heparin was used as an anticoagulant.…”

“…Values of free fatty acid (FFA) concentrations from the same individual animals from Fuglei et al (2000) were used in the present study. As a small carnivore living in a habitat with extreme fluctuations in food availability, photoperiod and temperature, the arctic fox is a very attractive model to study these novel hormones of weight-regulation and their possible interactions in seasonal body mass regulation.…”

Comparative nutrient digestibility of arctic foxes (Alopex lagopus) on Svalbard and farm-raised blue foxes (Alopex lagopus)

“…Four adult male foxes were randomly chosen out of eight males comprising the experimental animal stock at the Research station. They had been trapped in the near-by area of Ny-Alesund and kept captured for 1-2 years for other scientific purposes (Fuglei andØritsland, 1999, 2001;Fuglei et al, 2000;Fuglei, 2000). The age of the animals were at least 12 months (probably 14 months old) and average body weight at the start of the experiment was 3.80 kg (S.D.…”