Comparative Histological Examination of the Integument of Odontocete Flukes

Cetacean skin is noted for being exceptionally thick and being structurally different from the skin of terrestrial mammals in that it lacks hair, sebaceous glands, and sudoriferous glands. The caudal flukes of cetaceans are the primary propulsive structures, which are subjected to hydrodynamic flows and forces that differ from those experienced by the body. Based on the hydrodynamic function of the flukes, their integument is hypothesized to be histologically distinct from that of the body. The microanatomy of cetacean integument was examined to determine whether structural differences between the flukes arid dorsal body skin are present. Integument samples were collected from the dorsal body and five fluke locations for five odontocete species (Delphinus delphis, Stenella coeruleoalba, Tursiops truncates, Kogia breviceps, and Phocoena phocoena) and prepared for light microscopy. Statistically significant differences were observed in epidermal thickness and dermal papilla height between the dorsal skin arid skin of the fluke; and there were differences between epidermal thickness and dermal papilla height of the leading edge when compared to other locations on the fluke. Dermal papillae deeply penetrated many locations of the fluke, suggestive of functions associated with resisting shear forces, cell proliferation, thermoregulation, and tactile sensitivity.