Why did the chiton throw itself in a ball?
"To get on the other side," said Julia Sigwart, an evolutionary biologist at the University of Queens-Belfast in Northern Ireland.
About 500 million years ago, the pair Species of extinct trilobites became the first animals to roll into a ball for protection. The living doppelganger of the trilobite is a chiton. The covered shell of the marine mollusk drapes over the muscular body and the mucous membrane, giving it the appearance of a flattened piece of nigiri shrimp. But you're more likely to find it clinging to a tidal cliff than expecting sticks on a dinner plate.
In a number of laboratory experiments the doctor. Sigwart has shown that rolling into balls has more to do with helping chitons get to places where they can rejoin after losing support. She hopes these findings, published Wednesday in Biological Letters, provide evidence for a new argument: that chitons are capable of making decisions.
"People who think of chitons tend to think of them as primitive animals with a simple nervous system, not a lot of behavior," said Dr. Sigwart. "So this is an unexpected level of complexity compared to the assumptions of a textbook about these animals." .
Chitons sometimes roll defensively, for example, when they feel the need to protect their soft bodies when pressed, but usually they do not do much more than stick to residential surfaces, and from time to time they move.
When they deviate, they can collapse
The critical problem with chitons is that they are heavy, but not flexible enough to rotate and have no appendages, so when they accidentally land on their backs, they can't turn back. All they can do is arch and stick their foot out. If you're lucky, they touch what they can push you to go straight to yourself – or places to stick and stay safe.
The glue for your feet is so strong that if you lifted your chiton too hard from the rock, its body and armor tore off, leaving your foot behind. And that makes the leg an important element of their defense against hungry predators, ”Dr. Sigwart said.
In each experimental test, the researchers placed the chiton upside down in the middle of the test tank. They then added water from a larger chiton tank or from an ocher starfish tank.
Chitons can detect this natural predator odor. The researchers found that his chitons were three times less likely to spend reduced time than those who had not. These threatening chitons chose the arch and the driveway. It is an energy-intensive defense that can threaten the irradiation of my body, but can also reward the chiton, helping to find a safe place to survive.
Dr. Sigwart believes that, at some level, chitons are capable of weighing risk and reward. Other work from her lab says more complexity in the chiton nervous system, and that chitons have a real brain.
Additional studies will be required to confirm this notion. But Dr. Sigwart hopes for a greater appreciation of the neural complexity of the chiton.
"They don't have a head. They have a really weird body. These are animals that we find difficult to relate to. But they still make the same decision as we do," she said. -not like us. "