Glandular biofluorescence in fire salamanders ( <i>Salamandra salamandra</i> ): first evidence and ecological implications

Abstract With advances in imaging technologies and the growing availability of specialized lights and cameras, biofluorescence is increasingly recognized as a widespread trait with potential roles in the behavioural ecology of many tetrapods. Here, we report the first evidence of biofluorescence in the fire salamander (Salamandra salamandra), one of Europe’s most studied amphibians. Under UV illumination, S. salamandra exhibited conspicuous external fluorescence, mainly on the ventral and lateral surfaces and in glandular secretions. Histological analyses revealed that UV–violet excitation produces a broad blue–green fluorescence in the epidermis and granular glands, matching the emission of secretions and the speckled external pattern corresponding to glandular ducts. Fluorescence lifetime imaging revealed that glandular fluorophores differ from those in the epidermis and are also ubiquitous in blood components, suggesting that fluorescent compounds may be transported via the circulatory system, a feature previously known only in tree frogs. Additionally, a secondary yellow fluorescence was detected in the dermal chromatophore layer, excited exclusively by UV light. Notably, fluorescence from secretions persisted on substrates for over 24 h and fulfilled several criteria for ecological relevance, suggesting a communicative function for this trait and adding to the growing evidence of ecologically relevant fluorescence in amphibians.