A Functional Nexus between Photoperiod Acclimation, Torpor Expression and Somatic Fatty Acid Composition in a Heterothermic Mammal

Abstract

The seasonal changes in thermal physiology and torpor expression of many heterothermic mammals are controlled by photoperiod. As function at low body temperatures during torpor requires changes of tissue lipid composition, we tested for the first time whether and how fatty acids are affected by photoperiod acclimation in hamsters, Phodopus sungorus, a strongly photoperiodic species. We also examined changes in fatty acid composition in relation to those in morphology and thermal biology. Hamsters in short photoperiod had smaller reproductive organs and most had a reduced body mass in comparison to those in long photoperiod. Pelage colour of hamsters under short photoperiod was almost white while that of long photoperiod hamsters was grey-brown and black. Short photoperiod acclimation resulted in regular (28% of days) torpor use, whereas all hamsters in long photoperiod remained normothermic. The composition of total fatty acids differed between acclimation groups for brown adipose tissue (5 of 8 fatty acids), heart muscle (4 of 7 fatty acids) and leg muscle (3 of 11 fatty acids). Importantly, 54% of all fatty acids detected were correlated (r2 = 0.60 to 0.87) with the minimum surface temperature of individuals, but the responses of tissues differed. While some of the compositional changes of fatty acids were consistent with a ‘homeoviscous’ response, this was not the case for all, including the sums of saturated and unsaturated fatty acids, which did not differ between acclimation groups. Our data identify a possible nexus between photoperiod acclimation, morphology, reproductive biology, thermal biology and fatty acid composition. They suggest that some of the changes in thermal physiology are linked to the composition of tissue and organ fatty acids.

Effects of unsaturated fatty acids on torpor frequency and diet selection in Djungarian hamsters (Phodopus sungorus)

“…Nevertheless, acclimation of Djungarian hamsters to short photoperiod (SP) resulted in changes of tissue lipid composition in all examined tissues, i.e. heart, leg muscle and brown adipose tissue (Geiser et al, 2013). The fact that the composition of somatic lipids changed while food remained the same is in accordance with diet-independent remodelling of membranes before hibernation in alpine marmots (Marmota marmota) (Arnold et al, 2011).…”

Dietary protein supplementation and its consequences for intake, digestion, and physical activity of a carnivorous marsupial, Sminthopsis crassicaudata

“…By eating more protein and less lipids during exposure to high-protein diets, dunnarts may be satisfying their overall energy requirements by balancing between overconsumption of pro- Other studies have shown that adding dietary lipids can affect both energetics and torpor use in eutherians and marsupials alike (Bozinovic & Méndez, 1997;Contreras, Franco, Place, & Nespolo, 2014;Faherty, Campbell, Hilbig, & Yoder, 2017;Geiser, Klingenspor, & McAllan, 2013;Geiser, McAllan, Kenagy, & Hiebert, 2007;Geiser, Stahl, & Learmonth, 1992). However, polyunsaturation of lipids in the diet can strongly influence torpor use and torpor duration in mammals whose omnivorous or granivorous diets regularly include natural foods rich in these nutrients (Bozinovic & Méndez, 1997;Geiser et al, 1992Geiser et al, , 2007Geiser et al, , 2013. Few lipid-supplementation studies have been performed on strict carnivores to determine the effects of diet on torpor use in these mammals (Wilder et al, 2016).…”

The Chemistry of Cold: Mechanisms of Torpor Regulation in the Siberian Hamster

“…A role for fatty acids in torpor regulation has been discussed, since polyunsaturated fatty acids (PUFAs) have been shown to be beneficial for torpor in deep hibernators (68). In Siberian hamsters, fatty acid composition of tissues, in particular brown adipose tissue and heart, has been shown to change significantly after short-day adaptation independent of changes in dietary fat, but no clear increase of torpor frequency can be found upon substituting essential PUFAs (28,71). Not the absolute PUFA content but rather the ratio of different PUFAs might influence torpor behavior.…”