HARMS, H.K.; PAITZ, R.T.; BOWDEN, R.M.; JANZEN, F.J.; Iowa State Univ.; Iowa State Univ.; Illinois State Univ.; Iowa State Univ.: Is Resource Allocation to Eggs Constrained in the Painted Turtle?

Allocation to reproduction is expected to increase over time in long-lived organisms. Life-history theory predicts that females should invest less in reproduction early in life and more in growth and self-maintenance. This balance then shifts as females age and the relative value of each reproductive event increases. We examined this prediction in a long-lived vertebrate, the painted turtle (Chrysemys picta), accounting for both relative female age and clutch. We previously reported that younger females laid smaller eggs with similar lipid content (as % of dry yolk mass), and a higher percentage of water than those of older females. We also reported that first clutches, regardless of female age, had higher lipid and lower water contents than second clutches from the same female. Here we report data on the other major component of reptile eggs, protein. Utilizing the same eggs for protein analysis as those used for lipid and water content analyses, we found that proteins comprise approximately 75% of the dry mass of the yolk. The eggs of younger females contain absolutely less protein than eggs from older females, but younger females are laying significantly smaller eggs than are older females. As with lipids, the percentage of protein in yolks did not significantly vary with female age, but unlike lipids, protein content also did not vary between first and second clutches. These data are consistent with the interpretation that protein allocation to eggs is constrained. Females do appear to increase their investment in reproduction with age by producing larger eggs, but these eggs do not appear to be more lipid or protein rich than eggs from younger females.