Date of Award
8-2025
Culminating Project Type
Thesis
Styleguide
apa
Degree Name
Biological Sciences - Ecology and Natural Resources: M.S.
Department
Biology
College
College of Science and Engineering
First Advisor
Jennifer Y. Lamb
Second Advisor
Matthew P. Davis
Third Advisor
Sarah Z. Gibson
Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.
Keywords and Subject Headings
Gray Tree Frog Complex, Hylidae, biofluorescence, freshwater environment, amphibian, Minnesota
Abstract
Biofluorescence occurs when an organism absorbs shorter and then emits longer wavelengths of light. Most studies on biofluorescence focus on documenting fluorescence rather than on its biological functions. This study examines the potential ecological significance of biofluorescence in larval Gray Tree Frogs (Dryophytes chrysoscelis/versicolor). Tadpoles in this group develop large tails that appear orange-red under white light. Studies demonstrate that their tails deflect invertebrate predators. Their tails also fluoresce in the orange-red spectrum. If biofluorescence in tadpoles varies with the predator community, then it could function in signal enhancement for predator deflection. I quantified fluorescence, the invertebrate predator community, and the underwater light environment experienced by tadpoles. I collected environmental light spectra at two depths in three locations from eight wetland sites. At four of those sites, I also dip-netted for aquatic macroinvertebrates and tadpoles of the Gray Tree Frog Complex. I tested 47 tadpoles for fluorescence in response to blue (440 - 460 nm), cyan (490 - 515 nm), and green (510 - 540 nm) Nightsea Xite flashlights. I used digital photography to document reflected color and fluorescence. Images under white, blue, and cyan light were analyzed in RStudio (version 2024.12.1.563) using the countcolors package to quantify the proportion of the tail reflecting and fluorescing in the orange-red spectrum. I used spectrometry to quantify fluorescent emissions and calculate the peak wavelength and red chroma fluoresced by each tadpole. Biofluorescence varied across individuals. Wavelengths used to excite fluorescence occurred at depths in the wetlands used by tadpoles. Blue and cyan light produced striking orange-red fluorescence. Proportionally, this fluorescence contributed approximately 0.240 ± 0.048 and 0.248 ± 0.046 to total fluorescence under blue and cyan excitation, respectively. For some individuals, nearly 45% of the lateral surface of the tail fluoresced orange-red. I used general linear mixed effect models to explore the relationship between site-dependent variables, including predator density and diversity, and the orange-red fluorescence of tadpole tails. The percentage of orange-red pixels on the tail under white light and cyan excitation is positively correlated with invertebrate predator diversity. Based on this research, the orange-red biofluorescence on tadpoles of the Gray Tree Frog Complex may function in signal enhancement for predator deflection. This work adds to a limited pool of knowledge regarding biofluorescence in larval amphibians and provides insight into another possible function of biofluorescence in these vertebrates.
Recommended Citation
Miedema, Morgan R., "The Potential Ecological Significance of Biofluorescence in Tadpoles" (2025). Culminating Projects in Biology. 90.
https://repository.stcloudstate.edu/biol_etds/90
Comments/Acknowledgements
I would like to sincerely thank my advisor and committee chairperson, Dr. Jennifer Y. Lamb (SCSU). Dr. Lamb provided me with endless support, encouragement, and learning throughout my research. I have grown so much as a student and biologist during my time at St. Cloud State University (SCSU), and I have her to thank for much of that growth. I will forever be grateful for the opportunity to have Dr. Lamb as my advisor and mentor in herpetology. I would also like to thank my committee members, Drs. Matthew Davis and Sarah Gibson (SCSU). My committee gave me guidance and feedback during this research, providing insight from a non-herpetology perspective. Dr. Davis was gracious in allowing me to borrow some spectrometry equipment, which allowed for the smooth completion of this project. For their help in aquatic invertebrate identification, I thank Dr. Michael Bredeson (SCSU), Dr. Melissa Youngquist (Shedd Aquarium), and Dr. Kristopher Pitcher (United States Air Force).
Next, I would like to thank all the members of the Lamb Lab, current and past, who aided in this research and supported me as a person, including Alyssa Roberts, Kerri Beers, Jack Kosloske, Sam Skinner, and Dayton Johnson. I am grateful that the Lamb Lab is such a welcoming, supportive, and friendly group of herpetology enthusiasts. Whether it was through assisting in the field, giving feedback during lab meetings, or inviting me to take a needed break, all the members of the Lamb Lab helped with this project. I also thank my family members and partner, Eric Manuel. They have all been incredibly encouraging and supportive throughout my education.
This work was funded by an SCSU Student-Mentor Collaboration Grant and Grant in Herpetological Conservation and Research from the Minnesota Herpetological Society. This work was also funded by an SCSU Midcareer Grant to Dr. Lamb. All work was conducted according to research permits from the Minnesota Department of Natural Resources (Special Research Permit No. 35353; Parks and Trails Permit No. 202457), the Three Rivers Park District (Special Use Permit), and SCSU’s Institute for Animal Care and Use Committee (No. 17-130; Appendix C).