Scientists marvel at creatures' 'precise' body clock
A microscopic sea animal has been found to have a "genetic clock" which produces a specific 24-hour rhythm regulating its behaviour.
Calanus finmarchicus rise from the deep at night to feed on single-celled algae, before sinking again at dawn.
A study of Calanus finmarchicus found in Argyll's Loch Etive has shown sunlight is not needed as a trigger for this behaviour.
Scientists said they have been "amazed" by how precise the genetic clock is.
The study adds to research of Arctic zooplankton, which live through long months of polar winters.
The Oban-based Scottish Association for Marine Science (Sams) carried out the research on Loch Etive, where one of the only known isolated populations of Calanus finmarchicus is found.
Known as copepods, the creatures are food for large marine species.
Sams worked on the study with the Alfred Wegener Institute's Helmholtz Centre for Polar and Marine Research (AWI) and the University of Oldenburg in Germany.
The research on the creatures' body clock, also known as a circadian clock, has been published in the journal Current Biology.
Lead author Sören Häfker, of AWI, said: "We were amazed to see how precisely the genetic clock maintained its 24-hour rhythm without any external stimuli, and that we found the same rhythm under controlled laboratory conditions as we did in the natural habitat of Loch Etive."
Dr Kim Last of Sams, a co-author on the new study, added: "We have long looked to uncover the mysteries of zooplankton migrations and it appears that the circadian clock, much like our own, has a very important role to play in helping the animals be in the right place at the right time.
"Such fundamental mechanistic understanding is crucially important if we want to predict how marine ecosystems will respond to the complexities of future climate change."