A Report on Fluorescent Chameleons

Chameleons are small moving lizards with a prehensile tail, bulging eyes that rotate independently, a highly developed ability to change color, and recently the ability to glow in the dark. A new study conducted by German researchers found that the bones of Madagascar chameleons and some African chameleons have luminescent properties under ultraviolet light. The proteins, pigments, and other materials that are found in bone production assist the chameleons to glow under UV light. The fluorescent abilities are most likely adapted in chameleons who live in forested, moist environments with UV light surroundings. This finding unlocks several theories in the study of signaling between chameleons and sexual selection.

Not a lot is known about the function or development of fluorescence in organisms, but many scientists postulate that it could be used to protect themselves against excessive sunlight, recognize different species, or signal to potential mates. Fluorescence has been reported in various organisms, including plants, invertebrates, and marine vertebrate species (Pr?tzel et al.). It is uncommon in “terrestrial tetrapods” until the discovery of a South American tree frog, and recently the Madagascar and African chameleons. The study focuses on one type of chameleon, the genius Calumma; however, it suggests that this characteristic is probably present in eight out of twelve different species of chameleons.

The small rounded bony projections around the face, also known as the crests and tubercles of the head, as well as some of the bodies of many of the chameleons emanate blue fluorescence when stimulated with UV light. The tubercles arising out of the bones of the skull displace all but one thin layer of the epidermis to create a sort of transparent “window” onto the bone (Pr?tzel et al.). The number of these tubercles are sexually dimorphic, meaning males and females have different gender-driven characteristics, suggesting a signaling role of when the chameleons are ready to mate (Zachos). The purpose of the tubercles and crests has never been established; although it is probable that their function is used to recognize other species of chameleons as well as signaling and communication.

Many of the blue fluorescent patterns that are shown when exposed to UV light appear to cluster around the chameleon’s eyes and on the front of their heads; both areas are known to be important for communication between chameleons. It was found that on average the males presented more patterns than the females which suggests it may play a role in sexual selection (Weisberger). The designs that appear differ among certain chameleon species. For instance, most of the males in the genius Calumma, as well as some other species, have more fluorescent bones, tubercles, exposed than the females. This detection has led the researchers to believe that the fluorescence is not a coincidence, but instead an alternative defense apparatus intended to help the chameleons recognize members of the same species.

Chameleons are already known for their bulging eyes, communication skills, being able to shift shades, and now are one of the first reptiles known to display and possibly use luminescence to extend their communication. Their layers of skin allow for a transparent “window” to show on the bone giving them the blue hue when exposed to UV light. The different designs that appear onto the chameleons” head and sometimes body could indicate that the chameleons use this glowing ability to communicate with other species of chameleon to allow them to recognize different members as well as hypothetical mates.