Effects of acclimation and egg-incubation temperature on selected temperature by hatchling western painted turtles (Chrysemys picta bellii) Jeffrey W. Tamplin n , Andrew B. Cyr Department of Biology, University of Northern Iowa, 1227W 27th Street, Cedar Falls, IA 50614-0421, USA article info Article history: Received 22 August 2010 Accepted 2 September 2011 Available online 10 September 2011 Keywords: Thermoregulation Temperature gradient Incubation temperature Acclimation temperature Chrysemys Emydid turtles abstract The ability of hatchling turtles to detect environmental temperature differences and to effectively select preferred temperature is a function that critically impacts survival. In some turtle species, temperature preference may be influenced by embryonic and post-hatching conditions, such as egg-incubation and acclimation temperature. We tested for effects of embryonic incubation temperature (27.5 1C, 30 1C) and acclimation temperature (20 1C, 25 1C) on the selected temperature and movement patterns of 32 Chrysemys picta bellii (Reptilia: Emydidae) hatchlings in an aquatic thermal gradient of 14–34 1C and in single-temperature (20 1C, 25 1C) control tests. Among 10–11 month old hatchlings, acclimation temperature and egg-incubation temperature influenced temperature selection and movement patterns. Acclimation temperature affected activity and movement: in thermal gradient and single- temperature control tests, 25 1C-acclimated turtles relocated between chambers significantly more frequently than individuals acclimated to 20 1C. Acclimation temperature also affected temperature selection: 20 1C-acclimated turtles selected a specific temperature during gradient tests, but 25 1C- acclimated turtles did not. Among 20 1C-acclimated turtles, egg-incubation temperature was inversely related to selected temperature: hatchling turtles incubated at 27.5 1C selected the warmest tempera- ture available (34 1C); individuals incubated at 30 1C selected the coldest temperature (14 1C). These results suggest that interactions of environmental conditions may influence post-hatching thermo- regulatory behavior in C. picta bellii, a factor that ultimately affects fitness. & 2011 Elsevier Ltd. All rights reserved. 1. Introduction The ability of ectotherms, including turtles, to sense tempera- ture differences, to choose environments with a positive tem- perature flux, and to effectively thermoregulate is imperative in maintaining operative metabolic rates, and hence influences survival and fitness (Crawford et al., 1983; Hammond et al., 1988; Rome et al., 1992). Selection of thermal niches within particular habitats may be especially important for young turtles that, relative to adults, have low body mass and show increased rates of heating and cooling (Spotila and Gates, 1975). Juvenile turtles have a larger number of potential predators than adults, and to survive they must effectively balance thermoregulation with foraging and predator avoidance behavior. In addition, because warm temperatures may increase growth rates, it is particularly important that rapidly growing hatchlings maintain body temperatures that positively influence growth by selecting the appropriate thermal niches when available. Numerous environmental and developmental factors may influence temperature selection in hatchling and juvenile turtles. For instance, patterns of temperature selection in hatchling turtles may be affected by embryonic conditions, ontogenetic stage, acclimation temperature, and interactions thereof (O’Steen, 1998; Rhen and Lang, 1999; Bury et al., 2000; Nebeker and Bury, 2000; Birchard, 2004; Feltz and Tamplin, 2007; Tamplin, 2009; see Table 1). Studies assessing the thermoregulatory ability and temperature preference of juvenile turtles that do not involve potential contributing factors, such as different acclimation tem- peratures or exposure to various embryonic temperature regimes, suggest that young turtles are capable of effective thermoregula- tion and simply select temperatures close to their thermal optimum (Nebeker and Bury, 2001; Tamplin, 2006). Hatchling and juvenile turtles placed in laboratory-based aquatic thermal gradients typically select warm (27–33 1C) temperatures within a narrow range across a wide variety of taxa (e.g., Chelydra serpentina, Williamson et al., 1989, O’Steen, 1998, Bury et al., 2000; Apalone mutica, Nebeker and Bury, 2001; Apalone spinifera, Feltz and Tamplin, 2007; Glyptemys insculpta, Tamplin, 2006, 2009; Pseudemys nelsoni, Nebeker and Bury, 2000; and Trachemys scripta, Jarling et al., 1984, 1989, Bury et al., 2000). However, possible phylogenetic or population-based patterns of thermal Contents lists available at SciVerse ScienceDirect journal homepage: www.elsevier.com/locate/jtherbio Journal of Thermal Biology 0306-4565/$ - see front matter & 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.jtherbio.2011.09.001 n Corresponding author. Tel.: þ1 319 273 2327; fax: þ1 319 273 7125. E-mail address: jeff.tamplin@uni.edu (J.W. Tamplin). Journal of Thermal Biology 36 (2011) 507–514