Department of Biology, George Mason University, Fairfax, VA 22030, USA.
Department of Civil, Environmental, and Infrastructure Engineering, George Mason University, Fairfax, VA 22030, USA.
Biol Open. 2023 Oct 15;12(10). doi: 10.1242/bio.060114. Epub 2023 Nov 2.
Body coloration in ectotherms serves multiple biological functions, including avoiding predators, communicating with conspecific individuals, and involvement in thermoregulation. As ectotherms rely on environmental sources of heat to regulate their internal body temperature, stable melanistic body coloration or color change can be used to increase or decrease heat absorption and heat exchange with the environment. While melanistic coloration for thermoregulation functions to increase solar radiation absorption and consequently heating in many diurnal ectotherms, research on crepuscular and nocturnal ectotherms is lacking. Since crepuscular and nocturnal ectotherms generally absorb heat from the substrate, in these organisms melanistic coloration may have other primary functions beside thermoregulation. As such, in this work we hypothesized that the proportion of dorsal melanistic body coloration would not influence heating and cooling rates in the crepuscular gecko, Eublepharis macularius, and that changes in environmental temperature would not trigger color changes in this species. Temperature measurements of the geckos and of the environment were taken using infrared thermography and temperature loggers. Color data were obtained using objective photography and a newly developed custom software package. We found that body temperature reflected substrate temperatures, and that the proportion of melanistic coloration has no influence on heating or cooling rates or on color changes. These findings support that melanistic coloration in E. macularius may not be used for thermoregulation and strengthen the hypothesis that in animals active in low light conditions, melanistic coloration may be used instead for camouflage or other functions.
变温动物的体色具有多种生物学功能，包括躲避捕食者、与同种个体交流以及参与体温调节。由于变温动物依赖环境中的热源来调节内部体温，稳定的黑化体色或颜色变化可用于增加或减少与环境的热吸收和热交换。虽然在许多昼行性变温动物中，为了调节体温的黑化颜色可以增加太阳辐射吸收并因此加热，但对黄昏和夜间活动的变温动物的研究却很少。由于黄昏和夜间活动的变温动物通常从基质中吸收热量，因此在这些生物中，黑化颜色除了体温调节外可能还有其他主要功能。因此，在这项工作中，我们假设黄昏壁虎（Eublepharis macularius）背部黑化体色的比例不会影响其加热和冷却速率，并且环境温度的变化不会引发该物种的颜色变化。使用红外热成像仪和温度记录仪测量壁虎和环境的温度。使用客观摄影和新开发的自定义软件包获取颜色数据。我们发现体温反映了基质温度，并且黑化颜色的比例对加热或冷却速率或颜色变化没有影响。这些发现支持 E. macularius 中的黑化颜色可能不是用于体温调节的，并加强了这样的假设，即在低光照条件下活动的动物中，黑化颜色可能用于伪装或其他功能。
