A newly discovered microbe possesses a strange duality, reminiscent of a mixture of Dr. Jekyll and Mr. Hyde.
Euplotes gigatrox — is a tiny ciliate that usually floats peacefully in seawater, absorbing bacteria.
But over time, the clone colony will eventually be overwhelmed by a rogue cell, which will grow into a "supergiant" and begin a cannibalistic slaughter.
«"It's a single cell doing what we typically associate with animal development," says Ben Larson, a biologist at Rensselaer Polytechnic Institute in the US.
«"This expands our understanding of the capabilities of single-celled organisms and provides us with a new system for studying how cells control their shape and function.".
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Researchers have discovered E. gigatrox in seawater samples collected from a filtration system on the Caribbean island of Curaçao.
The organisms were cultured in artificial seawater, additionally providing them with a large amount of nutrients and bacteria.
For several months everything seemed normal.
But eventually, the researchers noticed that some cells had spontaneously grown to enormous sizes.
While the average cell was about 54 micrometers long, supergiants grew to about 140 micrometers.
And unfortunately for normal cells, these changes were more than just cosmetic.
The supergiants used their extra mass to hunt down normal clones, eating one cell approximately every 10 minutes.
Microscopic image of a supergiant cell Euplotes gigatrox, pursuing cells of normal size. (Larson et al., PNAS , 2026)
«"During cannibalism, the predator's cells 'overrun' the normal morphs until they become lodged in the mouth, where they are consumed," the researchers write.
«This is in stark contrast to the filter feeding of common morphotypes and other species Euplotes , where membranes generate an electric current that draws in bacteria and small protozoa.".
Luckily, there's a way to avoid being devoured by the supergiant by normal cells: just keep swimming. In your normal state E. gigatrox can "walk" on surfaces or float in liquids, performing graceful spiral movements.
However, supergiants are too bulky to swim and can only hunt along surfaces in a circular pattern. When researchers freed them from their shackles, they could only clumsily roll through the fluids until they reached the surface again.
«"The formation of supergiants is a trade-off," Larson says.
«"These cells become better hunters but worse swimmers, changing their trophic niche from feeding on bacteria to using a completely different type of prey.".
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However, this expansion in scale did not become a permanent change.
The researchers observed that all the supergiants returned to normal size within 24 hours. After this, a latent period apparently ensued during which they were unable to revert to supergiant size.
When the researchers divided the populations into normal cells and cells that had recently returned from supergiant status, they found that new supergiants formed from normal populations earlier and more often than from former supergiants.
Supergiant cells either divide equally into two cells of equal size or revert to normal-sized cells through a series of uneven cell divisions. (Larson et al., PNAS , 2026)
To determine what was happening in the cells during transformation, the researchers studied gene expression in normal cells, supergiant cells, and cells that had recently undergone reversion. They discovered two specific patterns of gene expression that appeared to play a key role.
«"One set of genes is activated during differentiation into supergiant cells and is partially retained in the reverted stage, while a second set of genes is activated only in reverted cells and likely accounts for the latency period," the researchers write.
As for the reasons for the transition of some cells into the supergiant phase, the researchers discovered several clues. These invariably appeared only after the population had completed its period of exponential growth and entered a more stable phase.
It is noteworthy that they will not appear if there are a lot of bacteria to feed on.
Only when other food sources become scarce does a small group of cells seem to enter their "Mr. Hyde phase" and begin to devour other cells.
A closer look revealed even greater diversity in these crops, including "winged" forms that, as Larson and his team note, "may serve a defensive function.".
Scanning electron microscope images show the supergiant (top), normal (middle), and winged (bottom) morphs E. gigatrox . Scale bar H–J' = 50 µm. (Larson et al., PNAS , 2026)
In all their experiments, the researchers report that supergiants never made up more than 5 percent of the total population.
They say this suggests that "supergiant formation may serve as a risk-hedging strategy for a subset of cells in a newly growing population when it reaches its limit.".
See also: Newly discovered organism may represent a whole new branch in the Tree of Life
This work is another reminder of those little horror stories that constantly unfold around us.
The results of the study were published in the journal «Proceedings of the National Academy of Sciences» .
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