Heterothermy in pouched mammals – a review

Abstract

Hibernation and daily torpor (i.e. temporal heterothermy) have been reported in many marsupial species of diverse families and are known to occur in ∼15% of all marsupials, which is a greater proportion than the percentage of heterothermic placentals. Therefore, we aimed to gather data on heterothermy, including minimal body temperature, torpor metabolic rate and torpor bout duration for marsupials, and relate these physiological variables to phylogeny and other physiological traits. Data from published studies on 41 marsupial species were available for the present analysis. Heterothermic marsupials ranged from small species such as planigales weighing 7 g to larger species such as quolls weighing up to 1000 g. We used the marsupial phylogeny to estimate various heterothermic traits where the current dataset was incomplete. The torpor metabolic rate in relation to basal metabolic rate (%) ranged from 5.2 to 62.8% in daily heterotherms and from 2.1 to 5.2% in marsupial hibernators, and was significantly correlated with the minimum body temperature in daily heterotherms (R 2 = 0.77, P < 0.001), but not in hibernators (R 2 = 0.10, P > 0.05). The mean torpor bout duration ranged from 2 to 15 h in daily heterotherms and from 85 to 342 h in hibernators, and decreased significantly with increasing minimum body temperature in daily heterotherms (R 2 = 0.31, P < 0.001), but was not significant in hibernators. Our results show that phylogeny has a significant influence on nearly all analysed individual traits and relationships between traits in daily heterotherms (n = 35), but not in hibernators (n = 6). However, allometric analyses show that many of the physiological parameters scale differently between hibernators and daily heterotherms.

Seasonal changes in energy expenditure, body temperature and activity patterns in llamas (Lama glama)

“…The statistical procedure has been described in detail elsewhere 83 . In brief, the phylogeny was derived from a published mammalian supertree which includes 4510 species with updated branch lengths derived from dated estimates of divergence times 84 .…”

“…To test for the generality of the relation between body mass and FMR in artiodactyls, published data 35 – 40 and our results, using the summer measurements, were assessed using the phlyogenetic generalized least squares approach (PGLS) 79 , 80 in order to account for the potential lack of independence between species, because of their shared evolutionary history 81 , 82 . The statistical procedure has been described in detail elsewhere 83 . In brief, the phylogeny was derived from a published mammalian supertree which includes 4510 species with updated branch lengths derived from dated estimates of divergence times 84 .…”

Evaluating evolutionary pressures and phylogenetic signal in earthworms: a case study - the number of typhlosole lamellae in Hormogastridae (Annelida, Oligochaeta)

“…Comparative methods have been used extensively on some animal groups, such as vertebrates, to study the correlation between phenotypic traits and environmental variables (Schondube, Herrera‐M & del Rio, ; Díaz, ; Medina et al ., ; Prevosti et al ., ; Boyles et al ., ; Edwards et al ., ; Riek & Geiser, ). Because of the non‐independence of species with shared evolutionary history, phylogenetic comparative methods are needed to take their relationships into account (Felsenstein, ).…”

Mitochondrial phenotype of marsupial torpor: Fuel metabolic switch in the Chilean mouse–opossum Thylamys elegans

“…The maintenance of thermal homeostasis can be a major challenge for endotherms when environmental conditions are energetically restrictive (i.e., periods of low environmental temperature and/or food scarcity). Physiological dormancy or torpor is a highly successful adaptation employed by various mammalian species to cope with these unfavourable conditions (Geiser and Kenagy, 1998; Riek and Geiser, ). Torpor is a phenotype characterized by an almost complete suppression of expensive process with the aim of reducing energy expenditure (Carey et al, ; Melvin and Andrews, ; Wang and Lee, ).…”