78385
Sharks: The Skinny
Presenter: Kasbati, Sabreena L.
Ecology and Evolutionary Biology
Mentor: Adam P. Summers
How shark skin structure relates to function is still uncertain. Shark skin is covered in many tooth-like structures called denticles embedded in the dermis and projecting through the epidermis. The number of denticles should affect the material properties of the skin in which they are embedded. The three objectives of this study were to 1) determine variation in mineral content (# of denticles) within shark species in different locations on the body and among shark species, 2) determine variation of skin strength and stiffness, and 3) compare mineral content with strength and stiffness. Shark skin from the dorsal and ventral surfaces of the head from three species (Isurus oxyrinchus, Mustelus lunulatus, and Prionace glauca) was heated to 500 degrees C in a muffle furnace for three hours to remove organic matter to determine mineral content, 16%, 28%, and 24%, respectively. Dorsal and ventral skin from the same three species plus Carcharhinus plumbeus were biomechanically tested, and data was analyzed to compute strength and stiffness. Mineral content, strength, and stiffness differed between species (p < 0.0001). Mineral content and strength did not differ within species, but stiffness did differ within species (p < 0.0001), ranging between 1x105 to 1x107 Pa. Mineral content did not affect strength or stiffness (p > 0.05). These results suggest that mineral content does not co-vary with strength and stiffness. Skin collagen fibers could contribute greatly to strength and stiffness. The mineralized denticles in the skin may be involved in locomotion more than in skin strength and stiffness.