The polka-dot tree frog ("Hypsiboas punctatus"), widely found in South America, was unintentionally discovered to be the first fluorescent amphibian in 2017. The fluorescence was traced to a new compound found in the lymph and skin glands. The main fluorescent compound is Hyloin-L1 and it gives a blue-green glow when exposed to violet or ultraviolet light. The scientists behind the discovery suggested that the fluorescence can be used for communication. They speculated that fluorescence possibly is relatively widespread among frogs. Only a few months later, fluorescence was discovered in the closely related "Hypsiboas atlanticus". Because it is linked to secretions from skin glands, they can also leave fluorescent markings on surfaces where they have been.