Profil endocrine chez la marmotte alpine (Marmota marmota). Seasonal endocrine profiles in the alpine marmot (M. marmota).

Résumé

The seasonal cycles of body mass, hibernation, reproduction and thyroïd function were studied in Alpine marmots maintained in outdoor enclosures, in Western France (C.E.B. Chizé [46 07'N, 0 25'W]). Plasma hormone concentrations (sexual steroids, LH, thyroxine) were measured mensually by radioimmunoassays adult marmots, a clear seasonal body mass cycle was observed with a maximum in early autumn (increase: 27-43 %) and a minimum in April (loss: 15-21%). The hibernating period occurred from November to mid-March the male, plasma testosterone concentrations were high (>0.8 ng/ml) from March to June-July and low (<0.4 ng/ml) from August to February. A short peak of LH occurred during the testicular recrudescence femelles, the absence of oestradiol and progesterone variations led us to the hypothesis of an induced ovulation both sexes, thyroxinemia was maximum from the end of spring to mid-autumn (140-l60 ng/ml) and decreased from early winter until April (110 ng/ml). The regular seasonal cycles, observed in captive marmots, seems to be consistent with the data available at the present time in the alpine habitat, and are essential for next investigations.