Environmentally induced variation in size, energy reserves and hydration of hatchling Painted Turtles, Chrysemys picta

Authors


Summary

  • 1The contents of newly constructed nests of Painted Turtles, Chrysemys picta (Schneider 1783), were manipulated by reciprocal transplant so that each of several nests received a complement of eggs from each of several females. The eggs were recovered from nests after 8 weeks and allowed to complete their incubation under standard conditions in the laboratory. The design of the experiment enabled us to distinguish between environmental and maternal effects on attributes of hatchlings.
  • 2Several measures of body size and energy reserve varied among turtles hatching from eggs that incubated in different nests, and certain of these measures varied also among turtles hatching from eggs that incubated in different layers within nests. The effects of nest and layer were substantial. For example, fat-free carcasses of hatchlings from one nest weighed 17% more than those of neonates from a second nest, but fat-free yolks from the former weighed only 53% as much as yolks from the latter.
  • 3Stepwise linear regression indicated that the size of hatchlings and the hydration and fat content of their carcasses were positively correlated with the net change in mass of eggs (which is an index to net water-exchange) while they incubated in the field. In contrast, both the fat and fat-free components of unused yolk were negatively correlated with change in mass of eggs. Although the statistical procedure is only correlative, the findings accord well with results of laboratory studies documenting a relationship between uptake of water by eggs, metabolism and growth by embryos, and size and condition of hatchlings.
  • 4Variation among hatchlings representative of different nests accounted for 24% of the statistical variance in mass of dry, fat-free carcasses; 29% of the variance in mass of dry, fat-free yolks; 19% of the variance in mass of storage fat in yolks; and 11% of the variance in mass of storage fat in carcasses. Additional variation was detected between the upper and lower layers of nests. Such environmentally induced variation probably affects survival of neonatal animals in the field.

Ancillary