杏吧原创

Chitons 鈥� flat molluscs common in tide pools 鈥� have shells that fluoresce a rich red-pink colour when exposed to blue light. The vibrant colours may, surprisingly, help the chitons avoid detection by predators 鈥� although other researchers aren鈥檛 convinced.

Chitons are an ancient branch of the mollusc family tree. Unlike their snail and clam relatives, chitons鈥� shells are built from a series of eight separate plates running along their backs.

Some chitons鈥� plates are , says at the Federal University of Santa Catarina in Brazil. Grimaldi and his colleagues wanted to know if the chitons might also hide from predators using patterns produced by biofluorescence, a phenomenon where, upon being illuminated, an organism鈥檚 surface re-emits light at a lower energy wavelength, observed as a different colour.

The team collected 44 chitons (Ischnoplax pectinata) from underneath intertidal boulders near Natal, Brazil, and brought them into the lab. When they photographed the chitons under blue light conditions, the animals鈥� back plates reflected an intense red-magenta.聽鈥淚t was amazing,鈥� says Grimaldi.

The plates鈥� fluorescent colour closely matched the fluorescent colours produced by red algae in the chiton鈥檚 habitat. So the researchers tested how the chitons might appear to their predators, which include octopuses, crabs, fish and gulls. They examined published data on the sensitivity of the predators鈥� eyes to a range of wavelengths, which suggested that all of the predators except octopuses would find it hard to pick out the chitons against an algae background.

However, at the University of South Carolina isn鈥檛 convinced the blue light used to induce the chitons鈥� biofluorescence adequately represents natural conditions. The researchers have 鈥渄ocumented an interesting natural phenomenon, but not one that is ecologically meaningful鈥�, says Speiser.

at the National Institute of Oceanography in India isn鈥檛 surprised by the findings, since biofluorescence is widespread in other mollusc groups, like snails and slugs.

鈥淏ehavioural studies with predators and mates are needed for a detailed understanding about the functions of fluorescence,鈥� says Chatragadda.