Meeting Abstract

P3.121  Thursday, Jan. 6  Plasticity of the stress response in variable environments: a reaction norm approach in the mangrove rivulus (Kryptolebias marmoratus) HANNINEN, AF*; EARLEY, RL; The University of Alabama; The University of Alabama amanda.hanninen@gmail.com

Plasticity in metabolic activity drives adaptive shifts in substrate use to maintain positive energy balance in variable environments, a process driven largely by the neuroendocrine stress response. Mangrove rivulus (Kryptolebias marmoratus) exist in ecosystems where tides fluctuate dramatically and they often occupy terrestrial habitats with limited food availability during tidal recessions. Rivulus are hermaphroditic and populations consist of homozygous strains that propagate through self-fertilization and generate genetically identical offspring spread. We explored within- and between-genotype variation in endocrine status along tidal and food availability gradients using a reaction norm approach. Because rivulus show age-dependent differences in reproductive investment, we expected animals to modulate their stress response according to future reproductive prospects. We employed three age groups (3-9; 10-15; > 15 mo) in two homozygous strains, divided evenly among three treatments (low tide; high tide; or changing tides [6h cycle]) under fed or fasted conditions. Hormones were collected before and after treatment using a water-borne method, and tissues were stored for future assays of key metabolic enzymes and reproductive investment. Initial analyses demonstrate that prolonged exposure to low tide and fasting trigger marked elevations in cortisol, notably in the youngest (i.e. most fecund) individuals of both isogenic strains. We discuss these results in light of ongoing work, which aims to reveal age- and strain-dependent patterns of endocrine/metabolic plasticity, growth, and reproductive investment in response to environmental stressors (reaction norms) in a powerful model system that allows strict genetic control.