THE RESPIRATORY METABOLISM OF TISSUES OF MARINE TELEOSTS IN RELATION TO ACTIVITY AND BODY SIZE l F. JOHN VERNBERG Department of Zoology, Duke University, Durham, North Carolina, and Marine Biological Laboratory, Woods Hole, Massachusetts Rates of oxygen uptake of tissues of fishes at different temperatures have been investigated by various workers (Fuhrman et al., 1944, brain of large-mouthed bass; Peiss and Field, 1950, brain and liver of polar cod and golden orfe; and Freeman, 1950, brain and muscle of goldfish). In 1953 Vernberg and Gray reported a direct correlation between general body activity and oxygen metabolic rate of excised brain. They also noted that within the size range of animals used, no relationship between body size and rate of oxygen uptake was evident in the toadfish and the pinfish. Although some workers reported a decrease in Qo 2 of tissues with increasing body size (Kayser, Le Breton and Schaeffer, 1925 ; Hawkins, 1928; Kleiber, 1941 ; Weymouth, Field and Kleiber, 1942; and Weymouth et al., 1944), other inves-tigators do not find this relationship to exist (Terroine and Roche, 1925 ; Grafe, 1925; Crandall and Smith, 1952; Bertalanffy and Pirozynski, 1953). Recently Krebs (1950), following a determination of the Qo 2 of five tissues of nine mammals, reported that there is not a simple correlation between body size and Qo 2 within the same species, and that, in general tissues of larger species have lower values than homologous values of tissues from smaller species. The present investigation was undertaken for two specific reasons. First, to continue the study of the relationship of activity and metabolism of various tissues in marine fishes. Secondly, to examine the relationship of tissue metabolism and body size in a group of poikilothermic vertebrates. MATERIALS AND METHODS The oxygen uptake of tissues was determined by the direct method of Warburg. Liver, muscle, and brain tissue from three species of marine teleost fishes, toadfish (Opsanus tau), scup (Stenotomus chrysops], and menhaden (Brevoortia tyrannus}, were studied. These three species of fishes were used because of their diverse habits and differences in general activity levels. Menhaden is an extremely active swimming form which normally lives and feeds at the surface of the ocean. On the other hand, the toadfish is a relatively inactive pugnacious bottom-dweller, and the scup is intermediate to these two in respect to activity. All animals were killed by severing the spinal cord in the region immediately posterior to the skull. Brain tissue was obtained by cutting off the roof of the skull and removing all tissue anterior to the vagal lobes. The brain was blotted 1 Aided by a grant from the Duke University Research Council. 360
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