Meeting Abstract
42.1 Monday, Jan. 5 Morphological and thermal properties of mammalian insulation: implications for the evolutionary transition to an aquatic lifestyle MOSTMAN-LIWANAG, H.E.*; BERTA, A.; COSTA, D.P.; BUDGE, S.M.; ABNEY, M.; ARNOULD, J.P.Y.; WILLIAMS, T.M.; UC Santa Cruz; San Diego State Univ., California; UC Santa Cruz; Dalhousie Univ., Halifax, Nova Scotia; UC Santa Barbara; Deakin Univ., Victoria, Australia; UC Santa Cruz mostman@biology.ucsc.edu
Over the course of their evolutionary history, several mammalian lineages secondarily invaded the aquatic environment. With aquatic specialization came an evolutionary change from reliance on external insulation provided by fur to internal insulation provided by blubber. The Carnivora includes three independent transitions to the marine environment; among these, pinnipeds retain both types of insulation, providing an ideal model for investigating factors that drove the convergent evolution of blubber across lineages. We compared fur and blubber characteristics among carnivores, determining quality of the insulation from gross morphology, molecular composition of fat, and thermal conductivity. We found that marine carnivores have significantly flatter, shorter, and more dense hairs than terrestrial carnivores (P<0.001 for each). Sea lions and phocids have thicker blubber layers (P<0.001) and lower fur densities than fur seals (P<0.001). Comparisons of lipid, water and fatty acid content indicated differences in the composition of the inner and outer regions of the blubber among groups (P<0.05), suggesting phocids and sea lions utilize the outer layer for insulation and the inner layer for energy storage. Fur seals, in contrast, rely on fur for insulation and blubber for energy storage. Comparisons of thermal conductivity revealed decreases in the insulative quality of fur in aquatic specialists, and concomitant increases in the insulative quality of blubber. Overall, these results indicate consistent changes in the insulation of mammals and evidence for convergent evolution of thermal traits across lineages.
