41.3 Thursday, Jan. 5 Endocrine and life history plasticity in an amphibious fish HANNINEN, AF*; DAVIS, AG; LEE, EA; WONG, SC; EARLEY, RL; University of Alabama; University of Alabama; University of Alabama; University of Alabama; University of Alabama firstname.lastname@example.org
Populations of the mangrove rivulus (Kryptolebias marmoratus), a self-fertilizing hermaphroditic fish, consist of a diverse set of heterozygous and homozygous, isogenic lineages. Natural populations often occupy terrestrial habitats during prolonged tidal recessions with limited food availability. We explored within- and between-genotype variation in cortisol, androgens [11-ketotestosterone (KT)], and estradiol along tidal and food availability gradients using a reaction norm approach. Given age-dependent differences in fecundity we expected animals to adjust their endocrine response according to future reproductive prospects. We employed 3 age groups (3-9;10-15;>15 mo.) in 2 isogenic lineages divided among 3 tidal treatments [low/high/alternating (every 6h)] under fed or fasted conditions. Hormones were collected before and after treatment using a water-borne method and tissues were stored for future assay of metabolic enzymes and reproductive investment. Initial analyses show that prolonged exposure to low tide trigger marked cortisol elevations in only young animals. There was no change in estradiol in high tide (control) animals following treatment however, low and alternating tide animals showed a significant decrease in estradiol relative to control animals. There was a significant decrease in KT in fasted animals of the alternating tide condition. Body mass and residual gonad mass also decreased significantly in fasted animals. Gonadosomatic index (GSI) was greater in control animals and young animals regardless of tidal regime. These results reveal environmentally driven, age dependent changes in hormones and reproductive investment through a powerful and genetically tractable model system.