Meeting Abstract

20.1  Jan. 5  Patterns of spermatogenesis and steroid hormone levels differ among reproductive phenotypes in bluegill sunfish KNAPP, R.*; NEFF, B.D.; LEARY, C.J.; Univ. of Oklahoma, Norman; Univ. of Western Ontario, London; Univ. of Oklahoma, Norman rknapp@ou.edu

In some species, males achieve reproductive success via one of several alternative reproductive tactics. In bluegill sunfish (Lepomis macrochirus), large �parental� males attract females to the nest to spawn and then provide sole parental care. Small �sneaker� males and intermediate-sized �satellite� males reproduce by cuckolding parental males. Previous studies have documented morph differences in sperm characteristics and sperm competition (Leach and Montgomerie 2000; Neff et al. 2003; Burness et al. 2004, 2005; Stolz and Neff 2006). In the present study, we characterized spermatogenesis and circulating steroid hormone levels on the day of spawning. Parental males� testes had proportionally more cysts containing spermatozoa, and proportionally fewer cysts containing spermatocytes, than did cuckolders� testes. Parental males also exhibited a relatively high degree of individual variation in overall patterns of spermatogenesis, a finding that may be related to whether or not the parental male will nest again later in the breeding season (Magee et al. 2006). There was a positive relationship between the percent of cysts containing spermatozoa and plasma cortisol levels in parental males. There was no such correlation for cuckolders. Across morphs, the percent of cysts containing spermatozoa and plasma 11-ketotestosterone levels were also positively correlated. We are using these morph differences in patterns of spermatogenesis and associated hormone levels as a starting point for understanding the proximate mechanisms underlying the documented morph differences in sperm characteristics and the likely morph differences in spawning frequency. Supported by NSF and NSERC.