Biofluorescent sexual dimorphism revealed in a southern Appalachian endemic salamander, Plethodon metcalfi

Abstract

Biofluorescence occurs when a living organism absorbs high energy light and reemits it at longer wavelengths. Many species within clades of vertebrates are known to fluoresce including mammals, reptiles, birds, and fish. Most, if not all, amphibians exhibit biofluorescence when exposed to either blue (440–460 nm) or ultra-violet (360–380 nm) wavelengths of light. Salamanders (Lissamphibia: Caudata) appear to consistently fluoresce in green wavelengths (520–560 nm) when excited by blue light. Biofluorescence is theorized to have many ecological functions including mate signaling, camouflage, and mimicry. Despite the discovery of their biofluorescence, its role in salamander ecology and behavior remains unresolved. In this study we present the first case of biofluorescent sexual dimorphism within Amphibia and the first documentation of the biofluorescent pattern of a salamander within the Plethodon jordani species complex. This sexually dimorphic trait was discovered in the southern Appalachian endemic species, Southern Gray-Cheeked Salamander (Plethodon metcalfi, Brimley in Proc Biol Soc Wash 25:135–140, 1912), and may extend into other species within the Plethodon jordani and Plethodon glutinosus species complexes. We propose that this sexually dimorphic trait could be related to fluorescence of ventral modified granular glands used in plethodontid chemosensory communication.