The Repository @ St. Cloud State

Open Access Knowledge and Scholarship

Date of Award


Culminating Project Type




Degree Name

Biological Sciences - Ecology and Natural Resources: M.S.




College of Science and Engineering

First Advisor

Jennifer Y. Lamb

Second Advisor

Matthew P. Davis

Third Advisor

Grover J. Brown, III

Fourth Advisor

Matthew A. Tornow

Creative Commons License

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.


I would first like to thank my primary advisor, Dr. Jennifer Lamb (SCSU). Dr. Lamb has been a tremendous amount of help and support over my time as an undergraduate and graduate student. She has taught me to be more confident in myself, my abilities, to be patient, and to have a huge passion for herpetology. I cannot thank her enough for how much she has enabled me to grow as a person and as a woman in STEM. She will forever be a huge inspiration in my life and someone I will always look up to. Next, I would like to thank my committee members, Dr. Matthew Davis (SCSU), Dr. Grover Brown (JSU), and Dr. Matthew Tornow (SCSU). Dr. D­avis was gracious in letting me borrow equipment such as a spectrometer and probe. I also want to thank him for his guidance throughout the project. Second, thank you to Dr. Brown, for adding to my excitement about turtles and for your wonderful support and advice. Lastly, thank you to Dr. Tornow for his advice and for providing insight from fields outside biology.

I would also like to thank other individuals who supported this research, including Dr. Althea Archer (USGS) and Dr. Beth Reinke (NEIU). Dr. Archer’s knowledge and skill in statistical analyses were critical. Dr. Reinke was insightful on many topics relating to turtle coloration and shared the design for the probe holder I used. Thank you also to all the Lamb Lab members who assisted on this project. To Maxim Kroll, thank you for your constant support and encouragement throughout this process. Your patience and kind heart never ceases to amaze me. To my mother, father, sister, and grandparents, I couldn’t have done this without your constant support and love throughout my journey at SCSU. I am unbelievably grateful to have such a loving, funny, and caring bunch of people by my side throughout not only all my hardships, but my accomplishments as well. I love you all.­­



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