Meeting Abstract

27.4  Saturday, Jan. 4 14:15  Anisotropy in the skin and blubber of killer whales suggest no hydrostatic function PORTER, ME*; WAINWRIGHT, DK; LOWE, AT; HALVORSEN, MB; SUMMERS, AP; Florida Atlantic University; Harvard University; University of Washington; Pacific Northwest National Laboratory; University of Washington, Friday Harbor Labs me.porter@fau.edu

Skin is a network of elastin and collagen fibers with variable amounts of organization. While alive, skin is under tension and has been shown to work as an exotendon in some species. The anisotropic properties, direction of elastic and collagen fibers, are largely attributed to the tendon like properties of skin. Marine mammals have a blubber layer located deep relative to the skin. The blubber layer is rich in proteoglycans, lipids and collagen, which change depending on diet and developmental stage. Our goal was to examine the anisotropic mechanical properties of skin and blubber from an orca Orcinus orca adult and calf. We obtained frozen skin and blubber samples from the head region of an adult female (L112) and from a male calf. After the specimen was thawed, we separated skin from the blubber layer with gross dissection. From each layer, we dissected samples to test both strength (MPa) and stiffness (MPa) from the longitudinal (cranial-caudal) or hoop (circumferential) orientation. We tested samples on a Synergie 100 test system (MTS, Eden Prairie, MN, USA) with a 500N load cell. We found maximum strength in the adult skin was 40% greater in the longitudinal compared to the hoop orientation. In the calf skin, a similar 30% increase in strength was found in the longitudinal orientation. Adult skin was four-fold stiffer in the longitudinal orientation relative to the hoop and calf skin was three times stiffer. If an orca were a pressurized vessel, the hoop strength expectation would be twice the longitudinal. Since the reverse is true we postulate that killer whale skin is not acting as a whole body exotendon.