Spawn of the triffid? Tiny organisms give us glimpse into complex evolutionary tale

Spawn of the triffid? Tiny organisms give us glimpse into complex evolutionary tale
Callophyllis: A type of red algae. Credit: Patrick Keeling Lab

Two newly discovered organisms point to the existence of an ancient organism that resembled a tiny version of the lumbering, human-eating science fiction plants known as 'triffids,' according to research in Nature.

The microscopic protists Rhodelphis limneticus and Rhodelphis marinus are genetically 'sisters' to , but couldn't be more different. Red algae are fleshy, large organisms with a simple genome that perform photosynthesis, just like . Rhodelphis are single-cell predators with a large, complex genome.

The two protists have a chloroplast, though it is not photosynthetic anymore, pointing to their close ties with plants in the distant past. They also have flagella, a whip-like structure which allows them to move and hunt for their dinner.

"Rhodelphis shows that there was a period of time when the ancestors of plants and algae probably absorbed sunlight to generate energy, while also swimming around eating things," says University of British Columbia (UBC) biologist Patrick Keeling, the senior researcher leading the study.

If we think of life as a big family, with and Rhodelphis as sisters, their ancient mother was more like a triffid than your standard plant. Triffids are the tall, mobile, featured in John Wyndham's 1951 novel The Day of the Triffids.

Spawn of the triffid? Tiny organisms give us glimpse into complex evolutionary tale
Chondracanthus exasperatus or Turkish Towel. A species of red algae. Credit: Patrick Keeling

This surprising evolutionary twist emphasizes the need for robust sampling in order to reconstruct a more complete picture of life.

"Most people don't look twice at like this under a microscope, and getting them into culture may be hard work but it's the only way to really see the true diversity of life," says Denis Tikhonenkov, the microbiologist who first captured the tiny predators and splits his time between UBC and the Russian Academy of Science.

"There are gems in nature we haven't found, and sadly the importance of 'old-fashioned' exploration is being forgotten," Keeling says. "These new lineages are a great example—making us realize we were previously seeing things backwards and now we recognize plants had ancestors we couldn't have imagined."

Keeling and Tikhonenkov worked on the project with the outstanding Russian Academy of Sciences protistologist Alexander Mylnikov, who died after a long illness shortly before the paper came to press.

Spawn of the triffid? Tiny organisms give us glimpse into complex evolutionary tale
Rhodelphis limneticus: You can see the tiny flagella that allow this protist to move and hunt. Credit: Denis Tikhonenkov

Explore further

Scientists discover first organism with chlorophyll genes that doesn't photosynthesize

More information: Non-photosynthetic predators are sister to red algae, Nature (2019). DOI: 10.1038/s41586-019-1398-6
Journal information: Nature

Citation: Spawn of the triffid? Tiny organisms give us glimpse into complex evolutionary tale (2019, July 17) retrieved 17 August 2019 from https://phys.org/news/2019-07-spawn-triffid-tiny-glimpse-complex.html
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Jul 18, 2019
So the ancestors could use photosynthesis AND move and eat things, while the descendants either just use photosynthesis or just move and eat things without being able to photosynthesize? Hmm, fascinating.

Jul 19, 2019
I speculate (with no evidence whatsoever) that the photosynthetic process in the ancestor was much less efficient than in algae today, necessitating ingesting and digesting energy rich compounds. That would have required motion, to reach food sources.

Over time, the photosynthesis in some populations could have become more efficient through natural selection, leading to a sedentary lifestyle (all you need to do is float where the sun shines, instead of wasting energy for locomotion)

In the other populations, the chloroplasts would have been lost (unnecessary baggage), as they became specialized hunters.

Jul 19, 2019
I speculate (with no evidence whatsoever) that the photosynthetic process in the ancestor was much less efficient than in algae today, necessitating ingesting and digesting energy rich compounds. That would have required motion, to reach food sources.

So they would have needed to previously have sufficiently efficient motion and consumption mechanisms. Seems like a chicken-or-the-egg sort of dilemma, doesn't it? I suppose we could guess they were able to get by originally with a poor version of one or the other due to special conditions (ouch!) and then evolved the other as an improvement, before specializing one way or the other. Well, the original population of life is supposed to have formed in a nutrient broth so rich that it could survive even though it was barely what we could identify as living.

Once you figure it had to have happened within a certain set of parameters, it's just a matter of using your imagination...

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