Dimensions of respiratory surfaces of the gills and skin in the Antarctic white-blooded fish, Chaenocephalus aceratus Lönnberg (Chaenichthyidae).

Gill arches of C. aceratus are long and bear a small number of filaments (9...11/cm). Density of secondary lamellae on filaments decreases from 19.4/mm to 17.8/mm in the specimen examined (815...1820 g). In contrast to that, surface area of an average secondary lamella increases in larger specimens and is from 0.489 mm2 to 0.664 mm2, respectively. The total surface area of secondary lamellae per 1 g of body weight is from about 193 to 159 mm2. The skin vascularization of C. aceratus is abundant. The average length of subepidermal capillaries per 1 mm2 of skin is 28.4, their surface area is about 1.3 mm2. The length of subepidermal capillaries per 1 g of body weight varies from 4,121 mm in 815 specimen to 2,695 mm in 1,820 g specimen; their surface area is about 184 mm2 and 120 mm2, respectively. The obtained results prove that the respiratory surface area of the gills in C. aceratus is as large as that of red-blooded fresh-water fishes of a moderate activity. The rich skin vascularization and a most advantageous ratio of body surface area to body weight indicate great possibilities of the skin in the exchange of respiratory gases.