Meeting Abstract
A central tenet of life-history theory predicts the existence of energetic trade-offs. A classic example of these trade-offs is the energetic investment in reproduction versus self-care, including growth. Most studies investigating such trade-offs are of a demographic nature; many fewer investigate the physiological mechanisms that facilitate such trade-offs. Painted turtles (Chrysemys picta) are an excellent organism in which to investigate physiological mechanisms associated with the trade-off between reproductive effort and growth because they exhibit indeterminate growth, meaning, for one, that they continue to grow even after reaching reproductive maturity. In this study, we investigated the putative role of insulin-like growth factors (IGF-1 and IGF-2) as hormonal mediators of energetic investment. We collected blood samples from known-age females after oviposition; size and age are positively correlated in this population. We found that while age is positively correlated with clutch size, age does not affect IGF-1 or IGF-2 levels. However, we did find a three-way interaction among IGF-1, IGF-2, and age on clutch size. This complex interaction is not surprising considering the multitude of effects IGFs have. These results superficially suggest that that how IGFs influence reproductive output varies based upon age. These results will be explored in greater detail in this talk.
