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

1. Temperature and moisture influence the development of embryonic reptiles in the laboratory but the importance of these variables to embryos developing in nature is a topic of debate. 2. We measured temperature 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 live mass and body size of hatchlings. 3. Average temperature in nests varied between 23.4 and 26.2 degrees C, and average water potential ranged 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 mass and produced relatively small hatchlings after short incubations, whereas eggs in other nests increased in mass and produced relatively large hatchlings after longer incubations. Net change in mass of eggs, length of incubation, and size and mass of hatchlings also were correlated more highly with water potential in nests than with temperature. 6. These findings lend support to the concept that availability of water in nests is more important than temperature in influencing survival, metabolism and growth of reptilian embryos.