P1.89 Wednesday, Jan. 4 Endocrine correlates of initial sexual differentiation in the Bluebanded Goby CONNOR, KR*; PRADHAN, DS; SOLOMON-LANE, TK; WILLIS, MC; NAUDE, PW; GROBER, MS; Georgia State Univ., Atlanta; Georgia State Univ., Atlanta; Georgia State Univ., Atlanta; Georgia State Univ., Atlanta; Univ. of Georgia, Athens; Georgia State Univ., Atlanta firstname.lastname@example.org
Socially controlled adult sex change is common in some fishes and is a marked divergence from the fixed sexes of mammals. While we know a great deal about the endocrine basis of initial sexual differentiation in mammals and adult sex change in fishes, little is known about endocrine regulation of initial sexual differentiation in sexually plastic animals, or its implications for adult plasticity. In many sex-changing fishes, planktonic larvae settle onto the reef and undergo metamorphosis into juveniles, during which sexual differentiation occurs. We collected newly recruited juvenile (N=14) Lythrypnus dalli, a bi-directional hermaphroditic fish species, and measured concentrations of 11-ketotestosterone (KT), a primary androgen indicator of male phenotype and behavior in most fish species, from water-borne steroids and whole body extractions. Average standard length and mass of recruits were 14.6 mm (range 12 - 17) and 43.7 mg (range 19.3 - 61.4) respectively. The length to width ratio of the genital papilla (a measure of sexual dimorphism in adults) ranged from male (>1.6) to female (±1) typical (range: 1.02 - 1.73; mean: 1.3 ± 0.21). Initial assays indicate the presence of KT in these maturing fish, and further analysis will examine the relationship between KT levels and both size and genital morphology. Additional studies will examine estradiol and testosterone with the goal to understand how sex steroid concentrations in recruits compare to those in sexually mature males and females. These studies will provide insights into the role of development and initial sexual differentiation in sexually plastic hermaphrodites.