KNAPP, R.; Univ. Oklahoma: Endocrine mediation of vertebrate alternative male reproductive phenotypes: the next generation of studies

In many species of animals, males may obtain reproductive success via one of several alternative reproductive tactics. In some of these species, behavioral variation is tightly correlated with morphological variation. Over the past decade or so, a concerted effort has begun to investigate endocrine mechanisms that underlie such discrete behavioral (and morphological) variation. In vertebrates, most research has focused on potential organizational or activational effects of steroid hormones (e.g., Moore 1991; Moore, Hews and Knapp 1998). Some of these studies have made it clear that, in addition to circulating hormone levels, one also must consider other aspects of the endocrine system, including hormone receptors, binding globulins and potential interactions among endocrine axes. In this presentation, I will review recent empirical and theoretical work on endocrine mechanisms and suggest possibilities for future investigation. In particular, I will discuss how individual variation in sensitivity to environmental conditions, particularly with respect to various stressors, may account for the existence of alternative male reproductive phenotypes in teleosts and other vertebrates. Along these lines, I will describe our current work with the reproductive phenotypes of longear sunfish (Lepomis megalotis) to determine the tissue-specific distribution and activity of two enzymes that are common to androgen and glucocorticoid synthesis and metabolism. A major goal of this work is to examine the potential role of steroidogenic enzymes in the transduction of environmental information to influence the expression of alternative male reproductive phenotypes. (Supported by the Oklahoma Center for the Advancement of Science and Technology)