Biological complexity: diurnal rhythms (Introduction)

by David Turell , Tuesday, February 02, 2021, 20:43 (1390 days ago) @ David Turell

Single celled ocean organisms have it:

https://www.sciencedaily.com/releases/2021/02/210201200019.htm

"Single-celled organisms in the open ocean use a diverse array of genetic tools to detect light, even in tiny amounts, and respond, according to a study published Feb. 1 in the Proceedings of the National Academy of Sciences.

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"Though invisible to the human eye, ocean microbes support all marine life, from sardines to whales. Knowing these communities' inner workings could reveal how they will fare under changing ocean conditions.

"'Just like rainforests generate oxygen and take up carbon dioxide, ocean organisms do the same thing in the world's oceans. People probably don't realize this, but these unicellular organisms are about as important as rainforests for our planet's functioning," Coesel said.

"By analyzing RNA filtered out of seawater samples collected throughout the day and night, the study identifies four main groups of photoreceptors, many of them new. This genetic activity uses light to trigger changes in the metabolism, growth, cell division, movements and death of marine organisms.

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"The researchers collected water samples far from shore and looked at all genetic activity from protists: single-celled organisms with a nucleus. They filtered the water to select organisms measuring between 200 nanometers to one-tenth of a millimeter across. These included photosynthetic organisms, like algae, which absorb light for energy, as well as other single-celled plankton that gain energy by consuming other organisms.

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"While the sun is up, these organisms gain energy and grow in size, and at night, when the ultraviolet light is less damaging to their DNA, they undergo cell division.

"'Daylight is important for ocean organisms, we know that, we take it for granted. But to see the rhythm of genetic activity during these four days, and the beautiful synchronicity, you realize just how powerful light is," Armbrust said."

Comment: Not surprising, and it shows the importance of a rotating Earth with day and night periods. Undoubtedly all organisms follow that rhythm.