Circadian rhythms in Mexican blind cavefish Astyanax mexicanus in the lab and in the field

• Published in: Nature communications 2013-11, Vol.4 (1), p.2769-2769, Article 2769
• Main Authors: Beale, Andrew, Guibal, Christophe, Tamai, T. Katherine, Klotz, Linda, Cowen, Sophie, Peyric, Elodie, Reynoso, Víctor H., Yamamoto, Yoshiyuki, Whitmore, David
• Format: Article
• Language: English
• Subjects: 631/181; 631/601/2722; 631/80/105; Animals; Behavior, Animal - physiology; Caves; Characidae - genetics; Characidae - physiology; Circadian Rhythm - physiology; DNA Repair - genetics; DNA Repair - physiology; Ecosystem; Gene Expression Regulation - radiation effects; Humanities and Social Sciences; Light; Mexico; Molecular Sequence Data; multidisciplinary; Period Circadian Proteins - genetics; Period Circadian Proteins - metabolism; Science; Science (multidisciplinary)
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms3769

Biological clocks have evolved as an adaptation to life on a rhythmic planet, synchronising physiological processes to the environmental light–dark cycle. Here we examine circadian clock function in Mexican blind cavefish Astyanax mexicanus and its surface counterpart. In the lab, adult surface fish show robust circadian rhythms in per1 , which are retained in cave populations, but with substantial alterations. These changes may be due to increased levels of light-inducible genes in cavefish, including clock repressor per2 . From a molecular standpoint, cavefish appear as if they experience ‘constant light’ rather than perpetual darkness. Micos River samples show similar per1 oscillations to those in the lab. However, data from Chica Cave shows complete repression of clock function, while expression of several light-responsive genes is raised, including DNA repair genes. We propose that altered expression of light-inducible genes provides a selective advantage to cavefish at the expense of a damped circadian oscillator. Body clocks modulate physiological processes to follow a day–night cycle, but whether animals exposed to constant darkness express circadian rhythms is unknown. Here the authors examine the expression of circadian genes in Mexican cavefish, and find that these resemble a pattern expected from exposure to constant daylight.