Early embryonic light detection improves survival

Classically, organization of the vertebrate circadian clock was seen as highly centralized in specific neural structures. Over recent years, this view has been transformed dramatically toward a more decentralized model with a number of distinct peripheral tissue clocks [1,2]. This is particularly true of zebrafish, where adult tissues contain autonomous circadian oscillators, which respond directly to light [3,4]. Cell lines derived from 24 hour old zebrafish embryos show the same circadian and light responsiveness as adult tissue [4,5].