Biofluorescence, the absorption of photons by biological tissues that are then reemitted at longer lower-energy wavelengths, occurs naturally in a broad range of organisms.
In recent years, biofluorescence in tetrapods has emerged as an increasingly common phenomenon, with many examples documented in mammals (Jeng 2019; Kohler et al. 2019; Anich et al. 2020), birds (Pearn et al. 2003; McGraw et al. 2007; Barreira et al. 2012; Camacho et al. 2019; Wilkinson et al. 2019), amphibians (Nowogrodzki 2017; Taboada et al. 2017a,b; Deschepper et al. 2018; Goutte et al. 2019; Gray 2019; Thompson et al. 2019; Lamb and Davis 2020; Whitcher 2020) and reptiles (Hulse 1971; Gruber and Sparks 2015; Prötzel et al. 2018, 2021; Sloggett 2018; Seiko and Terai 2019; Eipper et al. 2020; Eto 2020; Top et al. 2020; Mendyk 2021). The extent of this phenomenon in reptiles and its ecological and evolutionary underpinnings, however, remain poorly studied, though various fluorescent emission patterns have been identified in reptiles including the carapaces of sea turtles (Gruber and Sparks 2015), bony cranial protuberances of lizards, (Prötzel et al. 2018), skeletal elements of geckos (Sloggett 2018; Top et al. 2020), and the body scalation of various snakes and lizards (Hulse 1971; Seiko and Terai 2019; Eipper et al. 2020; Eto 2020; Prötzel et al. 2021). Taken together, these few examples suggest that biofluorescence may be more widespread in, and important to reptiles than previously envisaged.
Snakes offer new opportunities for exploring biofluorescence in reptiles. To date, biofluorescence has been recorded in several snake species across various families, including fossorial taxa such as the leptotyphlopid Rena humilis (Hulse 1971) and various members of the typhlopid genus Anilios (Eipper et al. 2020), the marine elapid Laticauda laticaudata (Seiko and Terai 2019), the terrestrial lamprophiids Limaformosa crossi and Mehelya poensis (Eto 2020), and rattlesnakes (Klauber 1956). Fluorescent pteridine-derived substances have also been extracted from the skin of three colubrids (Elaphe climacophora, E. quadrivirgata, Euprepiophis conspicillata) and the pitviper Gloydius blomhoffii (Odate et al. 1959). Given the dramatic differences in body size, morphology, coloration, ecology, behavior and phylogenetic relatedness between these taxa and considering that there are more than 3,800 extant snake species (Uetz et al. 2020) that vary widely in these characters, it is almost certain that additional examples of biofluorescence await discovery in snakes.
Recently, a cursory search for ultraviolet (UV) induced visible fluorescence in a private collection of captive reptiles by one of us (LP) revealed remarkable tail fluorescence in a captive-bred sibling group of juvenile Hagen’s Pitvipers, Trimeresurus hageni. Here, we dramatically increase the number of snake taxa known to exhibit biofluorescence by describing tail fluorescence in several genera of pitvipers (Viperidae: Crotalinae) for the first time.