Melanistic coloration does not influence thermoregulation in the crepuscular gecko Eublepharis macularius
Data files
Sep 20, 2023 version files 47.47 KB
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final_gecko_script.R
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FinalGeckoData.csv
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GeckoInfo.csv
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README.md
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variable_description.txt
Abstract
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 the function of melanistic coloration for thermoregulation increases solar radiation absorption for 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 besides 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.
README: Melanistic coloration does not influence thermoregulation in the crepuscular gecko Eublepharis macularius
The datasets described here are a combination of temperature measurements collected from both iButton sensors and FLIR thermal imaging, visible color values from multispectral photography, and physical characteristics (body length, mass, etc.).
Software used:
- R v4.2.1 for statistical analysis, with required packages loaded at the top of the included final_gecko_script.R
Description of data files:
FinalGeckoData.csv
Describes measurements collected from each individual during the experiments.
All temperature measurements are in degrees Celsius. Luminance (the measure of light intensity per pixel) is represented as a pixel value ranging from 0-255, with 0 being the darkest and 255 being the lightest.
Empty cells are due to missing data in data collection at that time period (specifically the body temp, substrate, and atmospheric measurements). Warm/cold/hide before and after measurements will always have an empty value corresponding to the beginning and end of each experiment, respectively. Individual EMM001 at time 4 has an empty value for Dark spot luminance because the clustering algorithm did not detect melanistic coloration in that image.
Variables are described as follows:
- ID: The unique identification number assigned to each individual tested.
- Average melanistic proportion: the average amount of melanistic proportion for each individual, calculated as the mean of Dark proportion.
- Date tested: The date on which individuals were tested. Ex. 802 = August, 02
- Time: The timepoint at which measurements were taken. 1 corresponds to the first measurements taken at the start of each experiment.
- Light spot luminance: The average luminance pixel value calculated from the non-melanistic coloration of an individual.
- Dark spot luminance: The average luminance pixel value calculated from the melanistic coloration of an individual.
- Light Proportion: The proportion of non-melanistic coloration relative to the dorsal area of the entire individual.
- Dark Proportion: The proportion of non-melanistic coloration relative to the dorsal area of the entire individual.
- Warm side: The temperature reading from the iButton placed over the heating pad at the time of capturing images.
- Warm 5 min before: The temperature reading from the iButton placed over the heating pad 5 minutes before capturing images.
- Warm 5 min after: The temperature reading from the iButton placed over the heating pad 5 minutes after capturing images.
- Cold side: The temperature reading from the iButton placed at the far end of the terrarium away from the heating pad at the time of capturing images.
- Cold 5 min before: The temperature reading from the iButton placed at the far end of the terrarium away from the heating pad 5 minutes before capturing images.
- Cold 5 min after: The temperature reading from the iButton placed at the far end of the terrarium away from the heating pad 5 minutes after capturing images.
- Hide: The temperature reading from the iButton placed underneath of the hide at the time of capturing images.
- Hide 5 min before: The temperature reading from the iButton placed underneath of the hide 5 minutes before capturing images.
- Hide 5 min after: The temperature reading from the iButton placed underneath of the hide 5 minutes after capturing images.
- Body temp: The body temperature of the individual at the time of image capture, calculated via the average eye temperature obtained from thermal imaging.
- Substrate: The substrate temperature of the terrarium flooring obtained from thermal imaging.
- Atmospheric: The temperature reading from the iButton placed next to the terrarium at the time of capturing images.
GeckoInfo.csv
Describes measurements collected from each individual before testing. Variables are described as follows:
- ID: The unique identification number assigned to each individual tested.
- Sex: The sex of the individual.
- Average melanistic proportion: the average amount of melanistic proportion for each individual, taken from the previous data file.
- Mass: the mass in grams of an individual, obtained via a digital balance used before the start of the experiment.
- SVL: The Snout-vent-length of each individual, measured before the start of the experiment.
*average melanistic proportion was included in GeckoInfo.csv for ease of use in the statistical code, but was calculated from images taken during the experiment.
Methods
Melanistic color data for each gecko were obtained by taking visible images using a full spectrum converted Canon 1300D with a Kolari Vision UV/IR cut filter (410-700nm transmission). Melanistic color pattern was then extracted from the images following a newly developed software pipeline. Step-by-step data color extraction protocol can be found at https://github.com/brandon-hastings/Lumeleon
Body temperature of each gecko has been obtained using an infrared camera (CAT S62 smartphone Pro camera).