HARMS, H.K.*; BOWDEN, R.M.: Variation in yolk allocation in painted turtles (Chrysemys picta)

Maternal allocation of nutrients to egg yolk in oviparous animals is increasingly recognized as a critical component of embryonic and neonatal fitness. Painted turtles (Chrysemys picta) yolk their eggs over a period spanning late fall to early summer. To examine potential differences in the composition of the yolk deposited at different times of the year, we stained yolks with potassium dichromate, a procedure previously validated using avian yolks. Due to the extended period of yolk deposition in turtles, we hypothesized that large regions consisting of fall-accumulated and spring-accumulated yolk would be present, as opposed to the strong concentric rings found in avian yolks. We were able to visualize several distinct regions of yolk, arranged in roughly concentric rings, which may correlate to fall and spring yolking. To determine whether these regions vary in composition, we will run radioimmunoassays to test for steroid hormone concentrations, which have been linked to phenotypic variation in neonatal turtles. Furthermore, because painted turtles often lay two clutches of eggs in a season, we will pay special attention to differential allocation patterns between early- and late-laid clutches.