Figure 1. Thermal dependence of heart rates of embryos and hatchlings in the turtles Chrysemys picta (a) and Graptemys pseudogeographica kohnii (b).

Heart rates were measured by non-invasive methods, and are expressed as mean ± standard error. Heart rates did not change with the developmental stage of embryos or with the age of hatchlings, but were greater for embryos than for hatchlings when the animals were tested at high temperatures. Specifically, Turkey's test indicated that significant differences occurred at 30 and 33°C in C. picta, and 25, 30 and 33.5°C in G. pseudogeographica kohnii.