Blind Circadian Clock of Cavefish Enlightens Scientists

Circadian clock serves as a physiological timer of organisms to anticipate and adapt to the day-night cycle. However, the molecular mechanisms supporting that the circadian clock is driven by the presence of absence of light is still incomplete. Thus, Nicola Cavallari of the University of Ferrera in Italy, together with other scientists studied a cavefish that has evolved for millions of years inhabiting in dark subterranean caves of Somalia. The cavefish exhibit striking adaptations to their extreme environment, such as complete eye degeneration. However, it still retain a circadian clock that ticks for a longer period of about 47 hours. The cavefish showed no responses to light.

The researchers found out that the blindness is not linked for its adaptation in the circadian clock. The reason for the "blind" clock is the mutations of the two widely expressed non-visual opsin photoreceptors namely melanopsin and TMT opsin. Results of the study could be used to further understand the evolution and the regulation of the circadian clock.

Read the free-access article at http://www.plosbiology.org/article/info%3Adoi%2F10.1371%2Fjournal.pbio.1001142.