The structure of the skin in the epauletted fruit bat (Epomophorus wahlbergi) wing and body trunk was studied with a view to understanding possible adaptations for gas metabolism and thermoregulation. In addition, gas exchange measurements were performed using a respirometer designed for the purpose. The body skin had an epidermis, a dermis with hair follicles and sweat glands and a fat-laden hypodermis. In contrast, the wing web skin was made up of a thin bilayered epidermis separated by a connective tissue core with collagen and elastic fibres and was devoid of hair follicles and sweat glands. The wings spanned 18-24 cm each, with about 753 cm(2) of surface exposed to air. The body skin epidermis was thick (61 +/- 3 mu m, SEM), the stratum corneum alone taking a third of it (21 +/- 3 mu m). In contrast, the wing web skin epidermis was thinner at 9.8 +/- 0.7 mu m, with a stratum corneum measuring 4.1 +/- 0.3 mu m (41%). The wing capillaries in the wing web skin ran in the middle of the connective tissue core, with a resultant surface-capillary diffusion distance of 26.8 +/- 3.2 mu m. The rate of oxygen consumption (VO2) of the wings alone and of the whole animal measured under light anaesthesia at ambient temperatures of 24 degrees C and 33 degrees C, averaged 6% and 10% of the total, respectively. Rate of carbon dioxide production had similar values. The membrane diffusing capacity for the wing web was estimated to be 0.019 ml O-2 min(-1) mmHg(-1). We conclude that in Epomophorus wahlbergi, the wing web has structural modifications that permit a substantial contribution to the total gas exchange.
