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Effects of growth hormone transgenesis on metabolic rate, exercise performance and hypoxia tolerance in tilapia hybrids

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Swimming respirometry was employed to compare inactive metabolic rate (Rr), maximum metabolic rate (Rmax), resultant aerobic scope and maximum sustainable (critical) swimming speed (Ucrit), in growth hormone transgenic (GHT) and wild-type (W) tilapia Oreochromis sp. hybrids. Although the Rr of GHT tilapia was significantly (58%) higher than their W conspecifics, there were no significant differences in their net aerobic scope because GHT tilapia exhibited a compensatory increase in Rmax that was equal to their net increase in Rr. As a consequence, the two groups had the same Ucrit. The GHT and W tilapia also exhibited the same capacity to regulate oxygen uptake during progressive hypoxia, despite the fact that the GHT fish were defending a higher demand for O2. The results indicate that ectopic expression of GH raises metabolic rate in tilapia, but the fish compensate for this metabolic load and preserve such physiological determinants of fitness as aerobic scope, swimming performance and tolerance of hypoxia.

Keywords: aerobic scope; citrate synthase; critical swimming speed; lactate; maximum metabolic rate; oxygen uptake

Document Type: Regular Paper


Affiliations: 1: School of Biosciences, University of Birmingham, Birmingham B15 2TT, U.K., 2: Division of Mammalian Cell Genetics, Centro de Ingeniería Genética y Biotecnologia, P. O. Box 6162, Havana, Cuba and 3: Marine Biological Laboratory, University of Copenhagen, Strandpromenaden 5, DK-3000, Helsingør, Denmark

Publication date: August 1, 2003

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