KNAPP, R.*; NEFF, B.D.; Univ. Oklahoma, Norman; Univ. Western Ontario, London, Canada: Sex steroids and cortisol in male bluegill sunfish: Correlations with reproductive tactic and stage of parental care

Across vertebrates, androgens and glucocorticoids influence behavior and mediate responses to environmental stimuli, especially with respect to reproductive behavior and function. We are investigating how these hormones 1) contribute to variation in reproductive behavior in a species with alternative reproductive tactics, and 2) change over the course of energetically expensive parental care. In bluegill (Lepomis macrochirus), large colorful �parental� males excavate a nest, attract females to spawn, and then care for and defend the young until the fry become free-swimming. Other �cuckolder� males do not defend nests, but rather sneak spawn or mimic females to gain access to the nest for spawning. Cuckolder males do not exhibit parental care. Previous work by Kindler et al. (1989. Gen. Comp. Endocrinol.) documented that androgen levels differ among the male phenotypes and over the course of nest establishment and parental care, but they did not measure cortisol levels. Thus, for the present study, we sampled bluegill on the day of spawning and daily over the course of parental care from a well-studied population in Lake Opinicon, Canada. We are determining how testosterone, 11-ketotestosterone, estradiol and cortisol correlate across reproductive phenotypes and over the period of parental care. Our findings will be discussed in the contexts of energetic costs of the different tactics and parental males� ability to vary the effort invested in parental care (Neff. 2003. Nature). Supported by NSF and NSERC.