Meeting Abstract
Organisms that rely on internal support structures often possess deformable body coverings. Such integuments found in pressurized, soft-bodied invertebrates can be tight fitting and feature tensile fibers that constrain deformation. In many vertebrates, a tight body covering may also serve to store elastic energy or transmit force generated by muscles to locomotory structures. Our understanding of the function of loose fitting body coverings is less clear as there may be multiple, varied, and interrelated benefits. Our preliminary survey suggested that the function of loose skins often falls into one or more of four distinct categories: to ensure maximal range of motion; to maximize surface area; for puncture resistance and wound closure; and to lubricate. Biological examples of loose skins for each category include: the wrinkly skins of naked mole rats do not impede joint motion while turning in tunnels; giant salamanders can uptake oxygen across the large surface area represented by their loose skins; the loose belly skin of large felids prevent damage from ungulate prey hoof kicks and loose octopus and rabbit skin tends to pucker around a cut in order to seal it; the folds of chameleon tongue skin reduces friction during ballistic protraction. To validate this categorization scheme, we investigate an especially loose-skinned animal as a model organism: the hagfish. Using histology, 3D reconstructions, high-speed videography, and material testing of the skin and the body core, we find that loose skin may be an adaptation that A) allows the body core to form tight, yet sliding, knots to clean off slime, feed, and escape, B) increases the surface area over which cutaneous nutrient uptake may occur and C) improves puncture resistance by increasing the energy required to pierce the skin.
