Date of Award
Culminating Project Type
Biological Sciences - Ecology and Natural Resources: M.S.
College of Science and Engineering
Jennifer Y. Lamb
Matthew P. Davis
Grover J. Brown, III
Matthew A. Tornow
Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.
Keywords and Subject Headings
freshwater turtle, autofluoresence, Emydidae, reptile, dichromatism
The broader goal of my thesis research was to see if coloration, either reflected or fluoresced, varied with sex and or body region in Western Painted Turtles (Chrysemys picta bellii). In Chapter 1, I compare the normalized red, green, and blue reflectance values, and mean brightness, among male (N = 47) and female (N = 22) turtles from six different regions of the body. These data were collected from multispectral images and analyzed in linear mixed effect regression models. In Chapter 2, I digitally imaged biofluorescence under ultraviolet (UV) or blue excitation lights for those same turtles and body regions. I quantified fluorescence intensity as mean grey pixel values for each color channel and calculated mean brightness. I used linear mixed effects models to analyze those data. I found that sex and body region interact and that both impact reflected color in Western Painted Turtles. Yellow chin stripes are significantly brighter and more colorful in males compared to females. Yellow stripes on the chin and limbs are also significantly brighter and more colorful than the plastral, humeral, or marginal scutes. All individuals biofluoresce under both UV and blue light. Under UV light, peak emissions are in the blue spectrum and average 499.453 ± 3.595 nm. Under blue light, peak emissions average 534.057 ± 2.101 nm, which is in the range of green light. Fluorescence intensity in response to UV light varies significantly with body region. Under blue light, sex and body region both significantly influence fluorescence intensity. Male Western Painted Turtles have significantly brighter biofluorescence compared to females when averaging across body regions. This work does not identify the function(s) of color or fluorescence in these turtles, but it is a step towards a greater understanding of freshwater turtle biology. Western Painted Turtles are sexually dichromatic in the colors they reflect, as well as in their fluorescence in response to blue light. This study lays the groundwork for future studies to test hypotheses about the role of color and biofluorescence in turtles, and it is the first to document biofluorescence in a freshwater turtle.
Richards, Bailey Rae, "Reflected Color and Biofluorescence in the Western Painted Turtle (Chrysemys picta bellii)" (2022). Culminating Projects in Biology. 57.