Meeting Abstract
P2.166 Monday, Jan. 5 Steroidogenic enzyme activity in the three alternative male reproductive morphs of bluegill sunfish CARLISLE, S.L.*; KNAPP, R.; NEFF, B.D.; Univ. of Oklahoma; Univ. of Oklahoma; Univ. of Western Ontario scarlisle@ou.edu
Among the great variety of reproductive modes exhibited by teleost fishes, one that has received considerable attention is the presence, within a single species, of males that practice distinct alternative reproductive tactics (ARTs). Bluegill sunfish (Lepomis macrochirus) are particularly interesting in this regard because they have three male morphs that differ in reproductive behavior, morphology, and physiology. Parental males court females and provide care for the resulting offspring. Two non-parental morphs, termed sneakers and satellites, use sneaking or female mimicry behaviors, respectively, to steal fertilizations from parental males. Among the morphs physiological differences are differences in circulating 11-ketotestosterone (KT) and cortisol levels and various sperm characteristics on the day of spawning (Neff, Fu and Gross 2003; Neff and Stoltz 2006; Knapp and Neff 2007). The morph difference in KT and cortisol is of particular interest for understanding endocrine mediation of ARTs because the biosynthetic pathways of these hormones have two enzymes in common: 11β-hydroxylase (11β-H) and 11β-hydroxysteroid dehydrogenase (11β-HSD). We hypothesize that the relative activity of these enzymes in different tissues plays a role in endocrine mediation of the morph differences in behavior and/or spermatogenesis. To begin to test this hypothesis, we are currently comparing the activity of 11β-H and 11β-HSD (measured as the amount of substrate converted to product/min/mg protein) in gonad, liver, and interrenal tissues. We will describe our findings and discuss the implications of our results for understanding the mechanisms by which steroid hormones mediate behavioral and physiological aspects of the male ARTs in bluegill and in other teleost species with ARTs.
