D. Fulgione, M. Trapanese, V. Maselli, D. Rippa, F. Itri, B. Avallone, R. Van Damme, D. M. Monti, and P. Raia
The ability of some animals to rapidly change colour fascinates and astounds us in equal measure. Such colour change is enabled by specialized cells called melanophores in the animal’s skin, and this phenomenon has been observed for instance in octopuses, chameleons and fiddler crabs. This ability allows the animal to use its colour as camouflage and blend into their background that is heterogeneous or constantly changing, in order to conceal it from its predators or prey. However, the mechanisms by which animals perceive their surroundings to match their colour to the background are still not clear.
Moorish geckos Tarentola mauritanica are known to turn darker or lighter depending on the tone of their surroundings, and Domenico Fulgione and his co-authors from University of Naples Federico II and University of Antwerp wanted to examine whether these geckos match their skin tone to their surroundings via the nervous system, endocrine system or local cell response. In order to test this, the authors brought wild-caught moorish geckos into the lab and as treatments covered their eyes or their trunk, and then put them inside terrariums covered by either black or white paper and with a transparent lid. The team then observed whether the geckos were still able to change their colour to match the tone of their surroundings.
Surprisingly, the blindfolded individuals still changed their colour consistently with their background, whereas when the geckos had their trunk covered they did not change colour, even when they could see their surroundings. This and examinations of opsin levels in tissue samples from various parts of the geckos’ body led the authors to conclude that the moorish geckos have melanophores on their trunk that are light-sensitive and react to the light reflectance levels of their surroundings, leading to the observed skin colour change. Although a similar phenomenon has been observed in some non-amniotes such as tilapia and cuttlefish, this study has been the first to show evidence of such cryptic colour change triggered by dermal light perception in amniotes.