Microbe turns into cannibalistic “Hulk” under plenty of food

cannibalistic supergiant – A newly discovered protist, Euplotes gigatrox, can abruptly switch from a regular single-celled form into “supergiants” that grow to more than twice their normal size and cannibalize smaller, genetically identical siblings. Researchers say the switch is report

By day. Euplotes gigatrox behaves like an ordinary single-celled grazer—one of the tiny protists that licks its way through bacteria and other microbes. But sometimes. in a moment that looks almost too dramatic for the microscopic world. a handful of them balloon into “supergiants” more than twice their regular size.

In that swollen state, the cells turn into cannibals. The giant protists eat smaller, genetically identical brethren. The shift can follow triggers that researchers say aren’t fully understood, but they report that it tends to happen when there is plenty of food.

The transformation was discovered by Ben Larson, a cell biologist at Rensselaer Polytechnic Institute in Troy, N.Y., who found the microbes in gunk scraped from an aquarium filter in Curaçao. The work was reported May 14 in the Proceedings of the National Academy of Sciences.

Larson describes the change as a staged process. “First, a cell gets a big mouth, and they start running around like crazy,” he said. In this early phase, the cells aren’t very good at cannibalism. But if an emerging “Hulk” manages to capture a sibling—or a cousin—in its enlarged mouth. the “body plan of the cell rescales. ” Larson said. From there, the cell grows into an enormous cannibalistic supergiant.

The two forms—regular size and supergiant—don’t just differ in scale. In the supergiant, the protist’s behavior is different enough to match its nickname. Besides cannibalism, the big cells walk in circles and stop swimming the way smaller cells do.

The physical setup matters, too. Euplotes gigatrox is a ciliate. a type of single-celled protist with hairlike cilia surrounding its mouth parts. including a large oval depression. In the supergiant form, the mouth sits behind the fringe of those hairlike cilia. In a side view described in the study coverage. a supergiant eats its smaller siblings by running over them and jamming them into its mouth.

There’s also a kind of reversibility that makes the phenomenon harder to dismiss as a one-way malfunction. The giants can return to regular size by dividing asymmetrically. In that process, the Hulks produce nine normal-size offspring each in a 24-hour period and up to 16 in 120 hours. Over time. as the giant cells continue those lopsided divisions. they shrink until they are back to normal size and behavior.

Even ordinary Euplotes gigatrox has its own baseline rhythm: normal size cells divide just once in 24 hours.

What’s most striking is that the transition isn’t superficial. Larson and colleagues found that up to 42 percent of the organism’s genes are involved in switching from regular size to supergiant—and back again. The scale of that genetic involvement suggests the transformation is coordinated, not accidental.

Understanding how a single-celled organism can so dramatically change form and behavior may help researchers connect fundamental mechanisms to bigger evolutionary questions, including how complex behaviors could arise in simpler life—and perhaps how multicellular life evolved.

The sequence—regular grazers that sometimes erupt into food-fueled cannibal supergiants. then shrink back through asymmetric division—already looks less like a random surprise and more like a full life-history strategy. When it comes to Euplotes gigatrox, the “Hulk” is not just a metaphor. It’s a measurable biological switch.

Euplotes gigatrox protist ciliate cannibalism supergiants cell biology genes asymmetric division Proceedings of the National Academy of Sciences