Meeting Abstract
While most odontocete cetaceans store their blubber lipids as triacylglycerols, the deep diving kogiids, physeterids, and ziphiids store their lipids primarily as wax esters (WE). To date, the thermal properties of only one species (Kogia breviceps) with WE-rich blubber have been investigated (Bagge et al. 2012). Increased lipid content provides enhanced blubber insulation, and Bagge et al. (2012) provided the first data that increased WE content may also increase insulative value. We hypothesized that the blubber of ziphiids, which are the deepest recorded divers of all cetaceans, possess blubber with enhanced insulative properties, as compared to other cetacean species. We examined the composition of the WE-rich blubber of the ziphiid Mesoplodon europaeus. The blubber of adult M. europaeus (n=4) had a higher lipid (81.23±2.82% wet mass) and WE (99.33±0.40%) content than that of K. breviceps (56.64±1.73% wet mass lipid, 82.1±3.80% WE). Blubber’s thermal properties were measured using a standard experimental setup (Dunkin et al. 2005, Bagge et al. 2012), and we present preliminary findings from two adult M. europaeus using the superficial heat flux disc method. The blubber of M. europaeus has conductivity (0.10-0.14 Wm-1°C-1) and conductance (2.95-3.60 Wm-2°C-1) values that are approximately half those reported for K. breviceps (Bagge et al. 2012). These results support those of Bagge et al. (2012) and suggest that both lipid content and lipid type influence blubber’s thermal properties. It appears that the extremely deep diving ziphiids, which can maximally spend two to three times longer at depth than any other cetacean, possess a blubber layer with enhanced insulative capability to maintain body temperature against water temperature changes that occur while diving.
