Fish Pigment Keeps Body Clock Ticking
The researchers suggested this could have some effect on the creature's
body clock, much like the effect of visible light on higher animals' pineal gland.
In many animals, light intensity affects nerve activity in the pineal gland, which is responsible for secreting hormones such as serotonin and melatonin. These hormones influence the animal's circadian rhythm, the cycle of activity and rest.
http://www.flmnh.ufl.edu/fish/InNews...gment2004.html