HARMS, H.K.; PAITZ, R.T.; BOWDEN, R.M.; JANZEN, F.J.; Iowa StateUniversity; Iowa StateUniversity; Iowa StateUniversity; Iowa StateUniversity: Yolk lipid allocation varies seasonally, but not with age, in the painted turtle

Although turtles are often thought to exhibit indeterminate growth, it appears that growth slows appreciably sometime after the onset of reproduction. However, because females are still growing rapidly during the first few years of reproduction, there is the potential for a trade-off between allocating resources for growth and allocating them for reproduction. Based on this potential trade-off, we predicted that older females would allocate more lipids to their yolks than younger females. We investigated lipid allocation to yolks in the painted turtle, Chrysemys picta, accounting for both relative female age and clutch. We found that younger females lay smaller eggs with less massive yolks than older females. Those yolks contained absolutely less lipid, but the proportion of lipids in the yolks did not vary with age. The proportion of lipids did, however, vary within the nesting season, with first clutches containing a significantly higher proportion of lipids than did second clutches. The proportion of water in the yolk varied both with age and with clutch; older females allocated less water than younger females, and first clutches contained less water than second clutches. Younger females have proportionally higher water content in their yolks, but still allocate the same proportion of lipids to their yolks as older females. We are currently investigating the possibility that this disparity could be due to variation in protein allocation, with older females allocating more proteins to their yolks.