Nice "z" word, right? I was tempted, also, to go with "zelatrix," which is the title of an older nun in charge of disciplining younger nuns, according to the much abridged definition at The Phrontistery. However, that just reminded me of this post by E.J. Wesley (scroll down for the nun in question) and I began to feel quite unoriginal.
Zeitgeber: from the German for "time giver," meaning "synchronizer," this word refers to external cues that help an organism sync up its internal clock to the earth's dark / light cycle. The process of synchronization is called entrainment.
Mark Sisson of Mark's Daily Apple notes that "The master mammalian circadian pacemaker is located in the hypothalamus, in a section known as the suprachiasmatic nucleus (SCN)." The mechanisms by which the SCN takes cues from the environment are three-fold:
the retino-hypothalamic tract, which directly delivers photic (light-derived) information; the geniculo-hypothalamic tract, which indirectly delivers photic information; and the raphe-hypothalamic tract, which uses serotonin to deliver non-photic information to the SCN. The SCN tells the pineal gland to secrete melatonin. Both photic information (like blue light) and non-photic information (like temperature, social cues, food availability, to name a few) act as zeitgebers with the ability to entrain (circadian synchronization in accordance with an outside cue is called entrainment) internal clocks.I like the idea of an alien race that takes subtle cues in through new and unexpected organ systems; or, equally, the potential for the discovery of larger, extra-circadian rhythms we had no idea existed.