Although regeneration is common in nature, two sea slugs take it to a new level. Elysia cf. marginate and E. atroviridis can decapitate themselves and regrow their entire body!
The body will continue to function for months, but it eventually dies. Meanwhile, the head will heal the wound and re-grow all its organs. Even its heart.
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This discovery was accidental.
Sayaka Mitoh and Yoichi Yusa study the live cycle of sea slugs. One day, the researchers noticed that one of the slugs popped off its head. The head was moving around on its own.
“We were surprised to see the head moving just after autotomy,” Mitoh reported . “We thought that it would die soon without a heart and other important organs, but we were surprised again to find that it regenerated the whole body.”
It takes the slugs three weeks to regenerate their body.
Within hours of ejecting their body, the heads can start feeding . It takes a couple of days for the wound around the neck to heal.
In a week, the heart will grow back. The rest of the body is restored in three weeks. But, it appears to be a young slug’s game. Older slugs often die during the process.
The slugs need to survive a week without a heart or any vital organs.
While the slug is regrowing their body, they must continue to fuel themselves. Their major food source is algae. But they don’t just eat it.
They can absorb it into their bodies and borrow their chloroplasts , which allow the slugs to photosynthesize energy. This is likely how the head can survive without a heart or any major organs.
There are two likely reasons the slugs developed this ability.
First, it could help them to evade predators. If an animal grabs a hold of its body, it could pop off its head to escape. Lizards, for instance, can pop off their tails to escape a predator. However, when the researchers simulated an attack, the slugs remained intact.
The second reason might be to remove parasites. If their body was infected with many parasites, regrowing their bodies would effectively solve the problem. Some slugs are known to self-digest infected body parts and regrow them. At this point, the researchers think this is the likely use.
The slugs must have a complex body plan.
This is the first known case of an animal autotomizing – detaching – their whole body. The next step is to better understand the process.
“As the shed body is often active for months, we may be able to study the mechanism and functions of kleptoplasty using living organs, tissues, or even cells,” Mitoh explained. “Such studies are almost completely lacking, as most studies on kleptoplasty in sacoglossans are done either at the genetic or individual levels.”
h/t: Science Alert
