This sea snail can lose its head and regenerate a new body in three weeks.

At least two species of Secoglosson sea snails are able to detach their heads from their bodies and then develop a completely new body, including the heart and other internal organs. The authors of a new study published in the current journal Biology say that the secret to the survival of scattered snails may lie in the algae that make up most of their diet.

It is a type of self-mutilation known as “bi totomi” in biological circles, and many species exhibit some kind of phenomenon, especially lizards and salamanders, which have their tails (awakened ot totomi) to get rid of predators (tails usually grow backwards). ). . Sea cucumbers can react to stressful situations by expelling their internal organs, which are produced later. Starfish can take their hands off; Sometimes those weapons grow into new starfish. It is very rare in mammals, but there are two species of African spiny mice that can shed their skin to escape the predator’s grip, regenerating all damaged tissues (including hair cells, sweat glands, fur and cartilage).

Other species of marine snails, except those used in this recent study, will respond to being handled leaving their “mantle skirts” (which form most of the dorsal surface area of ​​slugs). But the ability to separate the head from the whole body. Survive and not only surviving, but revival is an extreme form of autototomy that has not been seen to date.

Co-author Sayaka Mitoh is a graduate student at Nara Women’s University in Japan, working in Yochi Yusani’s lab. Researchers raise sea snails and study them during their laboratory-centered life. One day a few years ago, Mitoh was inspecting marine pellets and noticed that a Alicia Margineta—Haad lost his head. He was shocked to see that the head was still spinning in the tank, feeding the moss as if nothing was wrong. Even more surprising was the fact that the wound was found to be self-inflicted: the snail had cut off its own head, apparently after dissecting its throat tissue.

“We were shocked to see him shaking his head after the autotomy,” Mitoh said. “We thought he would die soon without a heart and other vital organs, but we were surprised he regenerated the whole body.” And it took only three weeks to do so.

Fascinated, she and Yusa decided to investigate further. They chose adult samples Alicia Margineta Descendants of sea snails collected in October 2018, collected in the lab at Domori Shore, Japan. They also selected sub-adult specimens of the respective species, Alicia atroviridis, Collected on Mukashima Island from April to July 2019. About 33 percent Alicia Margineta Samples lose their heads during their lifetime, and someone did it twice even after their body was rearranged for the first time.

Despite having no body (or kidneys, or heart, or intestines, or most reproductive organs), the head continues to move and function, despite feeding on regular algae. The wound on the neck closed within a day, and all the cut specimens were withdrawn from their bodies within about 20 days. Scattered corpses also continued to move to touch for days or months. But over time they faded and shrunk and eventually rotted. The authors write, “The heartbeat appears before the body decomposes.

Mitoh and Yusa reported similar findings for this Alicia atroviridis Samples. Many of them were hosting copodod parasites (Arthurius SP.), And two of those who lost their heads regenerated their bodies within a week. Another 48 percent of these samples lost body parts over time, eventually expelling the parasite. About a third of them withdrew their bodies; The rest died. Samples without parasites were not pouring their bodies properly.

As a supplementary experiment, for six Alicia Marinata The specimens, Mitoh and Yusa, inspired the psyche by gently tying a nylon wire to the groove of the neck – a place they suspected to be a “broken plane.” The tissue began to disintegrate significantly at the site within 16 to 18 hours, and all but one specimen ascended to their heads after 18 to 22 hours. (The final specimen finally landed its head nine days later, probably because the wire had moved away from the broken plane.) They also tried to mimic the predator’s attack by pinching the head of another specimen of the sea snail, but this did not lead to extinction.

“The heartbeat appears before the body decomposes.”

Unlike ot totomies in other species, these two types of sea snails do not seem to flow into their bodies in response to predator threats. The authors note that adult sea snails do not have many natural predators, and given how long it took the specimens to separate their heads from their bodies, it would not be a useful strategy to avoid predators in any way.

Based on the findings of their experiments, the authors suggest that the real function of this behavior is to kill parasites – at least Alicia AtroviridiA similar function has been observed in protozoan parasitic infected earthworms. The authors wrote that “alternatively, but not mutually exclusive with this idea, the autotomy by Secog Glossons can work to prevent entanglement in algae or to remove accumulated toxic chemicals,” the authors wrote.

Regarding the ability of the whole body to regenerate and eat algae without a functioning digestive system, Mitoh and Yusa noted that both species have digestive glands that cover most of the body, including the head. That gland is attached to specialized cells that are able to maintain the centers of photosynthesis – the centers of photosynthesis from the chlorophyll from the intake of the head broken down from the chlorophyll. The authors suggest that the internal urge for survival and regeneration is the result of internal photosynthesis (kleptoplasty), keeping sea snails alive even without the ability to digest food.

However, “the reason why the head can live without the heart and other organs is unclear,” the authors wrote, and is therefore a reason for further study. “Shed bodies often remain active for months, so we will be able to study the mechanism and functions of kleptoplasty using living organs, tissues or even cells,” Mitoh said. “Such studies are almost entirely lacking, as most studies on kleptoplasty in secular glosses are performed either at the genetic or individual level.”

Image list by Sayaka Mitoh