Meeting Abstract
S11-2.1 Monday, Jan. 7 Environmental influences on sex determination in flatfishes GODWIN, J*; LUCKENBACH, JA; HOLLER, BL; DANIELS, HV; BORSKI, RJ; North Carolina State University; National Oceanic and Atmospheric Administration; North Carolina State University; North Carolina State University; North Carolina State University John_Godwin@ncsu.edu
Flatfishes of several genera display unusual sex determination patterns where both genetic and environmental influences play important roles. Two well-studied species of Paralichthys flounders (southern flounder, P. lethostigma, and Japanese flounder, P. olivaceus) exhibit approximately 1:1 sex ratios when reared at intermediate temperatures, but male-skewed sex ratios when reared at either high or low temperatures. These rearing temperature effects extend to somatic development with male-biased temperatures also producing poorer growth. These growth differences may be adaptive, as female Paralichthys flounder grow larger than males. The mechanisms underlying temperature effects on growth involve conserved pathways in vertebrate sex determination. Sex determination can be manipulated with sex steroid hormones and female development is associated with elevated expression of gonadal aromatase and the transcription factor FoxL2 mRNA while male determination is associated with expression of Mullerian inhibiting substance mRNA. Other environmental influences can also influence sex determination. Rearing of southern flounder juveniles in light blue tanks increases the proportion of males relative to that observed with darker backgrounds and is associated with higher whole-body cortisol concentrations. Consistent with a role in mediating environmental influences on sex determination, exogenous cortisol masculinizes sex ratios in both Japanese and southern flounder. This linkage between the endocrine stress axis and conserved sex determination pathways may provide a mechanism for adaptive sex ratio modification in a spatially and temporally variable environment.
