Cutaneous respiration in Octopus vulgaris
The skin of Octopus vulgaris consumes considerable quantities of oxygen in vitro, averaging 4.55x10(-5)&plusmn;1.80x10(-5) ml mm-2 h-1 (mean &plusmn; s.d.), if a flow is maintained over the skin sample (N=32). The consumption is higher still in vivo, 11.36x10(-5)&plusmn;2.73x10(-5) ml mm-2 h-1 (N=8), suggesting an additional net import of oxygen through the skin when the blood system is intact. If a substantial boundary layer is allowed to develop, oxygen uptake in vitro falls to 2.09x10(-5)&plusmn;0.56x10(-5) ml mm-2 h-1 (N=15). The proportion of the animals' total oxygen consumption that cutaneous uptake will represent must thus depend on how much of the skin is exposed and how well it is ventilated. Estimates indicate that some 41 % of the total oxygen requirement of an animal at rest might be satisfied in this manner. During exercise, with water flowing over the entire surface of the animal, cutaneous uptake will increase but is nevertheless likely to form a smaller proportion (about 33 %) of the total uptake. In an animal curled up in its den and digesting a substantial meal, cutaneous uptake could shrink to as little as 3 % of the total. Similar results were obtained in a small number of pilot experiments with a range of octopod, sepioid and teuthoid species.
Wells
J