Meeting Abstract
47.1 Wednesday, Jan. 5 Sex differences in the endocrine response to social challenge despite genotypic uniformity in the mangrove rivulus (Kryptolebias marmoratus) EARLEY, Ryan L*; HUANG, Shu-Ping; FULLER, Adam; HANNINEN, Amanda; GARCIA, Mark; University of Alabama rlearley@bama.ua.edu
The mangrove rivulus (Kryptolebias marmoratus), a fish that inhabits turbulent mangrove ecosystems of Florida and the Caribbean, exist either as self-fertilizing hermaphrodites or males, distinguished by traits including a caudal ocellus (hermaphrodites) and orange coloration (males). Self-fertilization results in populations that consist of a remarkable number of completely homozygous, isogenic strains. Males are rare in most field locations, but can be generated in the laboratory by incubating eggs at temperatures below 20ºC. Temperature-dependent sex determination coupled with this fish’s unique population structure allowed us to generate genetically identical individuals with different functional sex (hermaphrodite vs. male). We established size-, strain- and sex-matched pairs in a small arena, allowed the pairs to fight until contest settlement, and collected hormones both before and after the fight using a water-borne collection method. We hypothesized that, despite genetic uniformity, males and hermaphrodites would exhibit different contest behaviors and mount different endocrine responses to social challenge. The dynamics of male vs. male contests were statistically indistinguishable from hermaphrodite vs. hermaphrodite contests. However, males of both strains showed significant elevations in 11-ketotestosterone in response to social challenge, while hermaphrodites showed no such response. Hermaphrodite winners showed higher estradiol concentrations than losers, a pattern not seen in males. We also report on cortisol, testosterone, and progesterone responses to contests. These results point strongly to the importance of epigenetic factors in differentiating endocrine responsiveness to social challenges between the sexes.
