It was when the research group was going to check out their farms of marine animals that they discovered that a skullless snail in their lab only consisted of a head but was still alive.
The body, which contains almost all vital organs such as the heart, kidney and reproductive parts, had been dumped.
Surprised by the result, they decided to find out what happened.
Dumps the body spontaneously
The study, published in Current Biology, shows that the marine shellless snail releases the body on its own.
After just one day, the wound on the head grows again and after another three weeks, a new body has grown out.
In the returned body, the heart continues to beat and the body responds to touch for up to several months afterwards, but no new head grows out.
It is called autotomy when animals get rid of a body part in order to protect themselves, it can be a tail or an appendix.
But it is a new discovery that an animal releases its entire body.
- This snail has an incredible ability for retraining that is amazing, says Kennet Lundin, marine biologist at the Gothenburg Museum of Natural History.
Photosynthesis saves the snail's life
The fact that the head manages to survive with hardly any organs is due to the snail's food.
They are one of the sea herbivores.
- The crux here is, how can you live without a stomach?
And the prerequisite for this particular group is that they eat algae.
In the algae there are chloroplasts, where photosynthesis takes place, and the snails keep the chloroplasts in their own cells, says Kennet Lundin.
In chloroplasts, the sun's rays are converted into energy.
Through the algae that the snail eats, they take over a set of genes that allow the snail to control the chloroplasts it has ingested.
In this way, the snail can live through photosynthesis, like a plant.
The parasite is the thief
Scientists do not know for sure why the marine snail chooses to decapitate itself, but there are many indications that they do so when they have been attacked by parasites.
In all discarded bodies, the researchers found parasites, but when the new body then grew out, they were completely healthy.
- In the cases where the head was off, there were parasites in the body, a kind of crustacean that chews up their genitals.
So in order for them to be able to multiply at all, they cut off the head and new organs and genitals grow out.
So that they can actually reproduce, says Kennet Lundin.
Only the young snails managed the process.
In individuals who were older, no new bodies grew out, while one of the younger snails in the experiment even generated a new body twice.
See the clip above where marine biologist Kennet Lundin explains how the snail can survive without a body.