Meeting Abstract
Blubber is a modified form of lipid-rich adipose tissue that is unique to marine mammals. The many functions of blubber include the primary storage of energy, thermoregulation, streamlining and buoyancy. Because of the unique characteristics of blubber, it is interesting that studies on the morphology of the adipocytes are limited. Previous studies have shown that blubber adipocyte morphology differs between age class and reproductive state among bottlenose dolphin populations; however, we do not know how cell size varies across species. Using tissue that was fixed and embedded in paraffin, slides were stained using hematoxylin and eosin stain in order to determine the morphological differences between the adipose of deep and shallow-diving odontocetes. The families of odontocetes used in this study were the family Delphinidae, Kogiidae, and Ziphiidae. Pig adipose was used as a terrestrial mammal comparison. Adipocyte cell size and aspect ratio were measured. Cell size varied between the blubber layers of all individuals studied, with the smallest cells observed in the outer blubber layer and the largest in the inner blubber layer. Ziphiidae had adipocytes in all blubber layers that were 2-3 times larger than those compared to the other odontocetes and other mammals (i.e. elephant seals, rats and dogs). The adipocyte characteristics in pig fat were similar to the Delphinidae and Kogiidae adipocytes and other mammals, suggesting that most mammalian adipocyte size is conserved. These variations in morphological adipocyte characteristics suggest the potential for phylogenetic differences between odontocete blubber. Cell size may also be affected by the storage and mobilization of lipid in adipocytes, as microvessel differences have also been observed between species.
