Meeting Abstract
Dolphin skin along the trunk of the body has a ridged texture that has been hypothesized to interact beneficially with the water during swimming. However, previous studies are limited in their ability to quantify surface roughness and three-dimensional surface structure. We use a molding technique to capture the skin texture of 5 live bottlenose dolphins (Tursiops truncatus) at various locations around the body, which we then analyze and compare to previous measurements of dolphin skin, as well as to other pelagic sharks and bony fishes capable of high-speed swimming. Analysis using a gel-based contact profilometry procedure allows us to reconstruct surface topography on 1.4 cm by 2.2 cm sized patches of skin, and to calculate metrics of surface roughness. We find that ridges do exist on the surface of the bottlenose dolphin, but these ridges are only 6 microns in height, compared to the 24 microns measured previously. Our measurements of ridge period have a range of 180-780 microns, which includes the range measured previously (560-710 microns). Bottlenose dolphin skin has an average roughness of 2.6 microns across 5 sites along the body. As a comparison, dolphins are rougher than extruded aluminum (0.06 microns), and about equal to trout covered in mucus (2.6 microns). Dolphins are smoother than many other large pelagic predators: bigeye tuna have roughness values of about 11 microns, marlin range from 12.5 to 68 microns, and pelagic sharks have values between 5 to 15 microns. Dolphin body skin is thus extremely smooth. The range of roughness values for different species suggests there are multiple solutions to the design of surface textures that could reduce drag in pelagic swimmers.
