A newly described ciliate, Euplotes gigatrox, can swell into “supergiants” more than twice its usual size and eat smaller, genetically identical siblings. The switch appears to be tied to plenty of food, and researchers found that the transformation runs throu
In a tank’s filter gunk from Curaçao, researchers found a microscopic drama: sometimes a normally sized protist starts to balloon into a cannibalistic “Hulk.”
Euplotes gigatrox is a single-celled protist—specifically. a ciliate—that resembles an insect and grazes on bacteria and other tiny microbes. But under certain conditions, a small number of these cells turn into “supergiants” more than twice their regular size. In that enlarged state, the huge cells cannibalize smaller, genetically identical brethren. The trigger for the change isn’t fully clear. but the shift tends to happen when there is plenty of food. researchers reported May 14 in the Proceedings of the National Academy of Sciences.
The transformation unfolds in stages. said Ben Larson. a cell biologist at Rensselaer Polytechnic Institute in Troy. N.Y. who discovered the microbes in gunk scraped from an aquarium filter in Curaçao. First. “a cell gets a big mouth. and they start running around like crazy.” In that early phase. Larson said they aren’t very good at cannibalism. But if a would-be Hulk manages to capture one of its siblings or cousins in its enlarged mouth. “the body plan of the cell rescales. and they grow up to be these just enormous cannibalistic supergiants.”.
Researchers say Euplotes gigatrox has two different forms: regular size and supergiant. They describe the supergiant as moving and eating in a way that contrasts sharply with its smaller counterpart. Besides cannibalism, the big cells walk in circles and no longer swim like smaller cells can. In images of the supergiant. the mouth sits behind the fringe of hairlike cilia. and the cell eats by running over smaller relatives and jamming them into its mouth.
The story doesn’t stop at becoming a giant. The “Hulks” can return to their former size by dividing asymmetrically. According to researchers, the Hulks can produce nine normal-size offspring each in a 24-hour period and up to 16 in 120 hours. Normal-size E. gigatrox, by comparison, divide just once in 24 hours. With each lopsided division, the giant cells shrink until they are back to normal size and behavior.
The genetic rewiring behind this switch is just as striking. Up to 42 percent of the organism’s genes are involved in the transitions from regular size to supergiant and back again. Larson and colleagues found. The ability of a single-celled organism to alter its behavior so dramatically—and then reverse course—may help researchers understand how simple organisms can develop complex behaviors. and perhaps how multicellular life evolved.
Euplotes gigatrox cannibalism ciliate protist supergiant cells cell transformation gene expression Proceedings of the National Academy of Sciences