Biofluorescence is the process of living organisms absorbing high energy wavelengths and releasing them at lower energy levels (Jeng 2019; Lamb and Davis 2020). The use of biofluorescence is known to be widespread among a large diversity of animals, where it is utilized in a variety of different ways, from communication to camouflage (Sparks et al. 2014; Marshall and Johnsen 2017; Jeng 2019; Lamb and Davis 2020). Recently terrestrial vertebrates are receiving more attention towards their uses of biofluorescence, with mammals, amphibians, birds, and other reptiles demonstrating varying levels of fluorescence (Jeng 2019; Paul and Mendyk 2021). Within non-avian reptiles, anoles (Alfonso et al. 2019; Mendyk and Augustine 2021), chameleons (Prötzel et al. 2018), geckos (Sloggett 2018; Top et al. 2020, Prötzel et al. 2021), snakes (Hulse 1971; Paul and Mendyk 2021), and turtles (Gruber and Sparks 2015) have all been shown to utilize fluorescence. To date, all lizards that have specifically demonstrated UV fluorescence have utilized their bones in tandem with other structures to fluoresce (Prötzel et al. 2018; Sloggett 2018; Alfonso et al. 2019).
The various methods in which these taxa utilize fluorescence are still being understood, but some conclusions such as snakes utilizing fluorescent tail lures to attract prey can be drawn (Mendyk and Augustine 2021). In chameleons, Prötzel et al. (2018) demonstrated that the boney protrusions that fluoresced may likely be used for mate selection due to the ability to contrast against vegetation. Similar findings have shown that some forest dwelling anoles that convergently possess boney protrusions also exhibit UV florescence (Alfonso et al. 2019; Mendyk and Augustine 2021). In geckos, Prötzel et al. (2021) has shown that Web-footed Geckos, Pachydactylus rangei, are able to exhibit multiple kinds of fluorescence due to the use of iridophores as well as bones, potentially for interspecific signaling. However, the uses of solely bone-based UV fluorescence in geckos are not a well understood mechanism and the first step is to document which species express this mechanism.
In Maui, Hawai’i, USA, there are four genera of naturalized nocturnal geckos and one recently introduced diurnal genus.
Currently, only geckos from the genus Hemidactylus have been shown to exhibit bone-based fluorescence (Mendyk et al. 2021), but not in the species that occur in Hawai’i. The current hypotheses for uses of UV florescence in geckos are that it is utilized for communication, mate selection, antipredator function, or that it is a part of the gekkonid lineage expressed by bright UV light (Sloggett 2018; Mendyk 2021; Prötzel et al. 2021). To further add to this body of research, I observed living and preserved specimens of diurnal and nocturnal geckos in order to detect visible UV bone florescence.