Gc. Packard et Mj. Packard, Environmentally induced variation in size, energy reserves and hydration of hatchling Painted Turtles, Chrysemys picta, FUNCT ECOL, 15(4), 2001, pp. 481-489
1. The contents of newly constructed nests of Painted Turtles, Chrysemys pi
cta (Schneider 1783), were manipulated by reciprocal transplant so that eac
h of several nests received a complement of eggs from each of several femal
es. The eggs were recovered from nests after 8 weeks and allowed to complet
e their incubation under standard conditions in the laboratory. The design
of the experiment enabled us to distinguish between environmental and mater
nal effects on attributes of hatchlings.
2. Several measures of body size and energy reserve varied among turtles ha
tching from eggs that incubated in different nests, and certain of these me
asures varied also among turtles hatching from eggs that incubated in diffe
rent layers within nests. The effects of nest and layer were substantial. F
or 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 for
mer weighed only 53% as much as yolks from the latter.
3. Stepwise linear regression indicated that the size of hatchlings and the
hydration and fat content of their carcasses were positively correlated wi
th 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.
4. Variation among hatchlings representative of different nests accounted f
or 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 l
ayers of nests. Such environmentally induced variation probably affects sur
vival of neonatal animals in the field.