Meeting Abstract

P3.133  Wednesday, Jan. 6  Morphology and Microanatomy of Harbor Porpoise (Phocoena phocoena) Dorsal Fin Tubercles GINTER, C.C.*; BÖTTGER, S.A.; FISH, F.E.; Texas A&M University; West Chester University; West Chester University ccginter@tamu.edu

The unique pattern of small tubercles on the leading edge of the dorsal fins of harbor porpoises (Phocoena phocoena) has been widely noted in the literature. The external morphology and microanatomy of the tubercles were analyzed. Measurements were taken of height and peak-to-peak distance of the tubercles using videomicroscopy (N = 12-19/fin). Mean height ranged from 0.38 ± 0.17 mm to 0.64 ± 0.25 mm and was significantly different among individual porpoises (p<0.001). Mean peak-to-peak distance ranged from 4.16 ± 1.97 mm to 5.64 ± 2.0 mm and did not significantly differ among porpoises. Samples of the dorsal fin leading edge, trailing edge and tubercles were taken for microanatomical comparison. The microstructure analysis revealed an epidermal thickness of 0.67-2.68 mm with the thickest epidermis at the site of the tubercles. The epidermis contained three distinct strata (=layers) including stratum corneum, spinosum and basale. The stratum corneum was significantly thickened in tubercles (p<0.001), over four times thicker than in the leading or trailing edge of the fin. The stratum spinosum contained unusual enclosures that appear to be lipid-filled. The stratum spinosum was significantly thinner (p<0.001) in the trailing edge than in the other two sites. There was no significant difference in the stratum basale (the germinal layer of the epidermis) among the three sites. A dermis with distinct dermal papillae and regular arrangements of adipose tissue and collagen fibers was also noted. Though the function of the tubercles is unknown, their position suggests that they may have hydrodynamic importance.