EFFECTS OF THE MICROCLIMATE IN NATURAL NESTS ON DEVELOPMENT OF EMBRYONIC PAINTED TURTLES, CHRYSEMYS-PICTA

1. Temperature and moisture influence the development of embryonic rep tiles in the laboratory but the importance of these variables to embry os developing in nature is a topic of debate. 2. We measured temperatu re and water potential in 12 nests of painted turtles, Chrysemys picta , and subsequently assessed the influence of these factors on survival by embryos, net change in mass of eggs, length of incubation, and liv e mass and body size of hatchlings. 3. Average temperature in nests va ried between 23.4 and 26.2 degrees C, and average water potential rang ed from -0.06 MPa to -2.11 MPa. 4. Hatching success varied from 33 to 100%, and was correlated more highly with the water potential in nests than with temperature. 5. Surviving eggs in some nests declined in ma ss and produced relatively small hatchlings after short incubations, w hereas eggs in other nests increased in mass and produced relatively l arge hatchlings after longer incubations. Net change in mass of eggs, length of incubation, and size and mass of hatchlings also were correl ated more highly with water potential in nests than with temperature. 6. These findings lend support to the concept that availability of wat er in nests is more important than temperature in influencing survival , metabolism and growth of reptilian embryos.