Androgen levels and energy metabolism in Oreochromis mossambicus

Two studies were conducted to test the relationship between androgens and routine metabolism in the Mozambique tilapia Oreochromis mossamhicus. In the first Study, endogenous levels of plasma levels of androgens and oxygen consumption rate were measured. In accordance with expectations routine metabolism corrected for metabolic body mass, was positively correlated with the behaviourally active metabolite of testosterone, 11-ketotestosterone, but not with testosterone itself. In the second Study levels of 11-ketotestosterone were experimentally elevated, which increased the lowest values of (corrected) routine metabolism, indicating a positive relationship with standard metabolism. These results show the importance of measuring reproductive hormones, and are supportive of the hypothesis that elevated levels of androgens are a costly trait. (C) 2004 The Fisheries Society of the British Isles.