Abstract

The blubber of cetaceans appears to serve three purposes; it fairs or provides contour to body surfaces; it insulates, and it stores lipids. While related, each of these functions requires conceptually different performance of the blubber layer. For instance, even in a wasted animal with marked depletion of fat from the blubber layer, the dorsal fin and the caudal ridge retain shape. Observations like this suggest that the structure and lipid dynamics of the blubber vary from site to site.

During the course of detailed necropsy of beach-stranded Cetaceans, we collected blubber samples from dorsal lateral and ventral aspects of the body at the level of the auditory meatus, the axilla, the leading edge of the fin, the trailing edge of the fin, and the anus (15 sites). Animals of 9 species were studied; the Atlantic bottlenose dolphin, Tursiops truncatus, the striped dolphin Stenella coeruleoalba, the spotted dolphin Stenella attenuata, Fraser's dolphin Lagenodelphis hosei, the long-finned Pilot Whale Globicephala macrorhynchus, the Antillean beaked whale Mesoplodon europaeus, the melon-headed whale Peponocephalus electra, the false killer whale Pseudorca crassidens, all from the western Gulf of Mexico, and the harbor porpoise Phocoena phocoena, from the North and Baltic Seas.

Samples were processed through alcohols to paraffin, with precautions to control shrinkage artifact, sectioned at 10 microns, stained and mounted on glass slides. Slides were photographed, and panels constructed to assemble samples into their respective locations. These may be studied by simple inspection, and various features may be measured with considerable precision.

Blubber structure among the cetaceans studied tends to be relatively consistent at all sites for all species, with formation of a relatively dense collagen layer at the upper and inner surfaces, with most fat cells concentrated in the center zone, providing a layered effect. The porpoise showed very thin inner and outer collagen, otherwise rather consistent density throughout the blubber. The epidermis of Phocoena is remarkably thick, even compared to much larger dolphins.

Further studies will apply this technique to bottlenose dolphins and to harbor porpoises collected at different times of the year. Using a system of measurements, we will attempt to determine the sites of greatest change in lipid deposition under different physiological conditions.