Meeting Abstract
47.2 Monday, Jan. 5 Early ontogenetic aromatase expression in two locally adapted populations of Atlantic silverside (Menidia menidia) with different forms of sex determination DUFFY, TA*; PICHA, ME; WON, ET; BORSKI, RJ; CONOVER, DO; Stony Brook University; North Carolina State University; North Carolina State University; North Carolina State University; Stony Brook University taduffy@ic.sunysb.edu
Aromatase cytochrome P450 (cyp450arom) is an important enzymatic mediator of sex determination in teleosts with genetic sex determination (GSD) and is likely to play a role in fish with temperature-dependent sex determination (TSD). We compared the ontogeny of aromatase expression in a population of Atlantic silversides (Menidia menidia) from South Carolina (SC) that exhibits TSD and a second from Nova Scotia, Canada (NS) that exhibits GSD. Embryos and 6mm larvae were sampled from 21C treatments, and 8-21mm larvae were reared under feminizing (15C) and masculinizing (28C) temperatures. We measured whole-body Cyp450arom expression in embryos and 6mm larvae (prior to the window of sex determination) and aromatase expression in the trunk (head removed) of larvae at 8, 15 and 21mm TL, bracketing the window of sex determination. No differences in Cyp450arom were detected between populations at the egg and 6mm stage, but expression increased in both populations from 8-21mm. Individual fish from NS exhibited the highest overall expression at both temperatures and showed evidence of male-female differences in expression in 15 and 21mm fish. Fish from SC displayed low levels of expression at 28C with increased expression in some 15 and 21mm individuals at 15C. Tissue distribution of aromatase indicated Cyp450arom was increased substantially in the ovaries relative to other tissues. These results indicate that cyp450arom expression is heightened in some fish, presumably females, during sex determination. Expression levels between populations and temperatures may indicate that the role Cyp450arom differs between fish with TSD and GSD.
