The anatomy and chemical composition of adipose tissue in wild wolverines(Gulo gulo)in northern Canada

Abstract

Adipose tissue was dissected completely from 25 adult male and five adult female wolverines shot between October and March, 1990–1992 in Northwest Territories, Canada. The gross mass, mean adipocyte volume, lipid, protein and collagen contents were measured in adipose tissue from 13 superficial and internal depots homologous to those of other terrestrial mammals. The total adipocyte complement was calculated from the mass of each depot and its site‐specific adipocyte volume. Almost all the adipose depots found in other terrestrial mammals were present in wolverines and site‐specific differences in adipocyte volume were similar to those of other species. No significant sex differences were detected. All depots except the cardiac adipose tissue enlarged with increasing fatness, but the superficial depots expanded faster than any of the internal depots and the posterior superficial depots enlarged slightly faster than the anterior depots. The partitioning of adipose tissue between superficial and intra‐abdominal depots, and between anterior and posterior superficial depots, changed with fatness and was consistent with predictions from allometric equations derived from data from other Carnivora. The total adipocyte complement was variable, with more than 70% of the specimens having 2–5 times as many adipocytes as predicted from allometric equations relating adipocyte complement to body mass in other carnivorous mammals. Consequently, the correlation between mean adipocyte volume and total dissectible adipose tissue was weak. Measurements of adipocyte volume from biopsies of adipose tissue, and indices based upon the mass of thickness of one or a few depots, would therefore not provide an accurate estimate of fatness. The concentration of collagen was higher in the superficial and intra‐abdominal adipose depots of specimens collected in mid‐winter than in homologous tissues of those killed in early winter, but there were no comparable seasonal changes in the abundance of lipid or non‐collagen protein.