Meeting Abstract
P1.158 Tuesday, Jan. 4 Hatching time and behavior underlie size hierarchy formation in wood frog tadpoles KARDON, Adam*; WARNE, Robin W.; CRESPI, Erica J.; Vassar College adkardon@vassar.edu
Wood frog tadpoles living in resource-limited conditions grow and develop at different rates, creating a size hierarchy among tadpoles that hatch at the same time. We tested the hypothesis that hatching time and individual behaviors are mechanisms that contribute to size hierarchy formation and maintenance. To determine whether growth and development trajectories vary with hatching order, we sampled tadpoles hatching at four different times (n=20 tadpoles/time point) from four egg clutches collected within 48 hours of laying, and tracked growth and development through metamorphosis. Although the first cohort of tadpoles to hatch was the smallest, they grew larger and metamorphosed sooner than the other cohorts. In a second experiment, we tested whether behaviors impose and reinforce size hierarchy formation, we set up six replicate populations of eight uniquely tagged tadpoles of similar body weights and development stage, then recoded individual swimming, foraging and resting behaviors. We found initial body size was inversely correlated with activity, and although smaller tadpoles tended to swim and forage more than larger tadpoles, they gained less weight over the course of the experiment. These findings suggest that both hatching order and behavior contribute to size hierarchy formation in wood frog tadpoles, but in unexpected ways. Without any social interactions, we showed that early hatching tadpoles exhibit the fastest growth and development rates; but small differences in size among competing tadpoles may alter these trajectories due to the expression of size-specific behaviors that lead to size hierarchies. Current studies are aimed at investigating the physiological and neurological mechanisms underlying these behavioral and growth predispositions associated with the formation of size hierarchies in wood frog tadpoles, including the influence of glucocorticoids and arginine vasotocin.
