Meet the Sea Slugs That Chop Off Their Heads and Then Grow New Bodies

From the days of the original BBC Planet EarthNature documentaries have brilliantly revealed the strangeness of life, but the recent behavior of a sea slug observed in a Japanese laboratory is enough to leave one speechless.

As strange as birds of paradise dancing and cleaning, as strange as bioluminescent marine life, as strange as jumping chicks – nothing will blow your mind like this video of a sea slug decapitating before spinning around like nothing happened.

Japanese researcher Sayaka Mitoh discovered that among the extensive collection of sacoglossan sea slugs at her university, the largest in the world, one of the eLisia marginata mysteriously he had had his head separated from his body.

Stranger still, his head was moving on its own, seemingly smoothly. Stranger still, in a matter of hours he began to eat, even though his kidneys, heart, sexual organs and digestive system were absent. Stranger still, survived for weeks before regenerating a whole new body.

Findings of this extraordinary regenerative capacity have been described by Ms Mitoh in an article titled Extreme Autotomy and Whole Body Regeneration in Photosynthetic Sea Slugs.

Autotomy is the scientific term for self-amputation, a common trait most commonly found in lizards such as newts and geckos, and also in crustaceans such as crabs and lobsters. Deliberately dissolving the links between the tail of a lizard or the leg of a crab allows them to escape predators that manage to grab them by the appendix.

However, autotomy of the head, the abandonment of the whole body, has never been observed in the animal kingdom.

Autotomy in sea slugs: in figures

Five of the 15 individuals raised in the laboratory ME. marginata, and a captured wild individual autotomized his head at some point during his life. One even did it twice.

In all cases, all major organs were left behind. In most cases, the head moved immediately, began feeding on algae within a few hours, and the neck wound was completely healed within a day.

Young individuals regenerated their entire bodies in an average of 20 days, while older individuals never regenerated and eventually died. Their discarded bodies reacted to tactile stimuli immediately and continued to do so for months in some cases. Eventually though they would break down, though the heart would continue to beat until moments before the highest stage of breakdown.

Mrs. Mitoh recorded a video of the whole process here, with wonderful music to make it less disturbing.

But why?

Two theories categorized the study of this remarkable phenomenon. The first was the constant cofactor of internal parasites present in the body at the time of autotomy.

The purpose behind getting rid of the body is presumed to be a way to prevent parasites from destroying the organism completely, as in all cases of members of another species E. atroviridis, autotomized their bodies, they were infected with internal parasites.

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It is not a perfect hypothesis, since ME. marginata he never had parasites in the cases in which he autotomized. It is unlikely, says Mitoh in her article, that it is related to predation, as “adult sacoglossi generally have few predators due to their cryptic coloration and the presence of toxic chemicals incorporated into their food.”

“Our experiments also showed that the autotomy of ME. marginata it took several hours, which is not effective in preventing predation, and that mimicked predator attacks did not induce autotomy. ” writes Mithoh.

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As for how they survive and regenerate so quickly, the answer requires expanding your idea of ​​what an animal is. The digestive gland of slugs is actually a single organ that spans most of the surface of their bodies, even over their heads, that is lined by cells that actually steal chloroplasts from algae, cells that react to the light.

The theft of plant cells leads to the creation of a new type of cell known as cleptoplast, which allows them, once decapitated, to continue living generating energy like plants through photosynthesis, even when they do not have a heart and there is no form physics to digest food.

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The discovery must be one of the most amazing sets of evolutionary equipment ever observed, and for Ms. Mitoh, her work watching slugs decapitate themselves strangely represents the frontiers of biological science.

(CLOCK the video of the autotomized sea slug below).

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