The Impossible Salamander: Aberrant Coloration as a Result of Metal Toxicity, Crypsis, or Light Exposure?

• Main Author: Harmon, Wendy Allison
• Format: Dissertation
• Language: English
• Published: ProQuest Dissertations & Theses 01-01-2018
• Subjects: Biology; Ecology; Histology; Physiology
• ISBN: 9780438000728; 0438000722

The Buck Creek Serpentine Barrens in Clay County, North Carolina is an unusual habitat comprised of a pine savannah with endemic plant species underlain by serpentinite rock. The area is drained by a stream with a mostly open canopy. Most Desmognathus monticola (Seal Salamanders) living in the Barrens stream have bright yellow patches on their skin, although this population is genetically similar to normally-colored populations of D. monticola. My research explored whether this unusual coloration was due to: 1) trace metals from the serpentinite rock, 2) phenotypic plasticity for crypsis against the lightly colored serpentine rock on the stream bottom, or 3) excessive light exposure and decreased shade. I found that metals were unlikely to cause the yellow coloration because the metals of concern were at low concentrations in the stream water. Moreover, there were no differences in white blood cell counts or liver mass between Barrens and non-Barrens (control) populations, suggesting that there was no ongoing immunological response to or accumulation of toxic metals. The Barrens salamanders did have less epithelial pigment than control salamanders. Salamanders from both Barrens and control populations became more yellow in every crypsis lab experiment, whether exposed to light, dark, yellow, or red backgrounds. Another experiment found that the yellow coloration of salamanders was affected by salamander population source, light level they were exposed to, and calcium concentration, but luminosity (brightness) of the salamanders was not affected by any factors in that experiment. Understanding the environmental stimuli that induce this morphological change in these salamanders’ integument, and if these morphological changes are unique to this population, will help to shed insight upon a unique part of North Carolina’s landscape diversity.