Living at extremes: development at the edges of viable temperature under constant and fluctuating conditions.

In the painted turtle (Chrysemys picta) and the red-eared slider (Trachemys scripta), the temperature that eggs are exposed to during incubation influences many traits of the developing embryo. We tested the effect of fluctuating- versus constant-temperature incubation regimes at the high and low ends of the viable developmental temperature range to assess the effect of incubation environment on offspring development. Eggs were incubated in four treatments: 23 degrees C constant, 23 degrees +/- 3 degrees C, 31 degrees C constant, and 31 degrees +/- 3 degrees C.

Experimental test of the effects of fluctuating incubation temperatures on hatchling phenotype.

In the painted turtle (Chrysemys picta) and red-eared slider turtle (Trachemys scripta), the temperature that eggs are exposed to during incubation determines the sex of the developing embryo. Constant temperature incubation experiments have shown that for each of these species there is a pivotal temperature that produces a 1:1 sex ratio; higher temperatures bias sex ratios toward females, and lower temperatures toward males. Few studies have examined how fluctuating temperatures, as would be experienced in natural nests, affect hatchling phenotype.