STRUNTZ, D.J.; MCLELLAN, W.A.; GAY, D.M.; DILLAMAN, R.M.; PABST, D.A.: Blubber development in bottlenose dolphins (Tursiops truncatus)

Blubber, the highly derived, lipid-rich, hypodermis of cetaceans, functions in thermoregulation, metabolic energy storage, buoyancy control, streamlining, and locomotion. It is comprised of adipocytes surrounded by a collagen and elastic fiber matrix. Our goal was to investigate the development of this specialized hypodermis by studying lateral flanking blubber from bottlenose dolphins in two age classes: neonates and adults. Blubber samples were collected from freshly-dead, robust specimens that stranded along the coasts of North Carolina and Virginia. Samples were prepared using standard histological methods, viewed by light microscopy, and images of the blubber were captured digitally. We analyzed images through the depth of the blubber and measured morphological and structural features including adipocyte size, shape, and numbers, and the relative abundance of extracellular fibers (ECF). Our sampling r�gime was designed to permit investigation of differences that may occur through both the depth of the blubber and between age classes. Preliminary results indicate that in both neonates and adults, adipocyte size and ECF densities vary through the depth of the blubber with the largest adipoctyes and minimum ECF densities occurring in the mid-hypodermis. Adult adipocytes in the mid-hypodermis were approximately three times larger than adipocytes in the mid-hypodermis of neonates. Interestingly, through-depth counts of adipocytes were similar in both groups. These preliminary results suggest that blubber depth is increased during growth by changing cell size rather than cell number.