Biofluorescence in Morelia, Malayopython and Python: first reports for the Pythonidae

Abstract

Ultraviolet (UV) induced biofluorescence occurs when living organisms are exposed to UV light and the absorbed short wavelengths of light are re-emitted into longer wavelengths of light (Lamb and Davis, 2020). Within Squamata, the group with the most reports of biofluorescence are lizards (Font and Molina-Borja, 2004; Prötzel et al., 2018, 2021; Maria et al., 2022; Top et al., 2020; Mendyk 2021; Manunza and Columbo, 2022; Barends and Bester 2023; Scanarini et al., 2023) while snakes have fewer records (Seiko and Terai, 2019; Eipper et al., 2020; Eto 2020; Maria et al., 2022; Fuentes Magallon et al., 2021; Paul and Mendyk, 2021; Mendyk 2023). Much of the reported UV fluorescence in Squamata is bone-based, which is the result of the natural fluorescence of bones, related to collagen present in bones (Bachman and Ellis, 1965). It is often seen in taxonomic groups with translucent skin such as geckos which allows fluorescence of the underlying skeleton (Manunza and Columbo, 2022). In other cases, bony tubercles protrude from the skull like in chameleons (Prötzel et al., 2018) and Anolis barbatus (Mendyk and Augustine, 2021) or the lizards possess osteoderms as in Scincidae (Brecko and Pauwels, 2024) that are visible through their scales, and fluoresce under UV light. Except for sandboas (Erycidae), no other snakes to date are known to possess osteoderms (Frýdlová et al., 2023). Hence, bone-induced UV fluorescence probably does not occur within snakes. UV fluorescence in snakes is more likely to be skin-based and induced by chemical compounds in the skin layers. In the mid-20th century, fluorescent pteridine-derived substances have been found in the skin of a pitviper (Gloydius blomhoffii) and in three colubrids (Elaphe climacophora, E. quadrivirgata, Euprepiophis conspicillata) (Odate et al., 1959). These substances could potentially be the chemical compounds responsible for UV fluorescence in snakes. Very little is known regarding the function of UV fluorescence in snakes. Although, it has been suggested that UV fluorescence in the tails of pitvipers enhances caudal luring or acts as an antipredator response against attackers (Paul and Mendyk, 2021). While checking live reptile specimens in pet shops and private collections, we noted that within the Pythonidae several specimens of Morelia viridis (Schlegel, 1872) showed UV fluorescence. We therefore examined additional specimens from multiple species within the Pythonidae, both dead (freshly frozen and ethanolpreserved) and alive.

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