Physiological Ecology of Overwintering in the Hatchling Painted Turtle: Multiple‐Scale Variation in Response to Environmental Stress

• Published in: Physiological and biochemical zoology 2004-01, Vol.77 (1), p.74-99
• Main Authors: Costanzo, Jon P., Dinkelacker, Stephen A., Iverson, John B., Lee, Jr, Richard E.
• Format: Article
• Language: English
• Subjects: Adaptation, Physiological - physiology; Analysis of Variance; Animal nesting; Animals; Blood Glucose; Blood plasma; Body Water; Body Weights and Measures; Cold Temperature; Eggs; Energy Metabolism - physiology; Freezing; Freshwater; Hibernation - physiology; Indiana; Lactates; Lipids; Lipids - analysis; Nebraska; Overwintering; Reproduction - physiology; Seasons; Soil - analysis; Soil inoculation; Soil water; Turtles; Turtles - physiology; Weather
• ISSN: 1522-2152; 1537-5293
• DOI: 10.1086/378141

We integrated field and laboratory studies in an investigation of water balance, energy use, and mechanisms of cold‐hardiness in hatchling painted turtles (Chrysemys picta) indigenous to west‐central Nebraska (Chrysemys picta bellii) and northern Indiana (Chrysemys picta marginata) during the winters of 1999–2000 and 2000–2001. We examined 184 nests, 80 of which provided the hatchlings ( \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $n=580$ \end{document} ) and/or samples of soil used in laboratory analyses. Whereas winter 1999–2000 was relatively dry and mild, the following winter was wet and cold; serendipitously, the contrast illuminated a marked plasticity in physiological response to environmental stress. Physiological and cold‐hardiness responses of turtles also varied between study locales, largely owing to differences in precipitation and edaphics and the lower prevailing and minimum nest temperatures (to −13.2°C) encountered by Nebraska turtles. In Nebraska, winter mortality occurred within 12.5% (1999–2000) and 42.3% (2000–2001) of the sampled nests; no turtles died in the Indiana nests. Laboratory studies of the mechanisms of cold‐hardiness used by hatchlingC. pictashowed that resistance to inoculative freezing and capacity for freeze tolerance increased as winter approached. However, the level of inoculation resistance strongly depended on the physical characteristics of nest soil, as well as its moisture content, which varied seasonally. Risk of inoculative freezing (and mortality) was greatest in midwinter when nest temperatures were lowest and soil moisture and activity of constituent organic ice nuclei were highest. Water balance in overwintering hatchlings was closely linked to dynamics of precipitation and soil moisture, whereas energy use and the size of the energy reserve available to hatchlings in spring depended on the winter thermal regime. Acute chilling resulted in hyperglycemia and hyperlactemia, which persisted throughout winter; this response may be c