Tokyo, Japan - You've probably heard of animals that are able to lose and then regenerate a tail or limb. But did you know that there are species that can do even better?

Scientists led by Sayaka Mitoh from Nara Women's University have now discovered the true masters of regeneration: two species of the sacoglossan sea slug that shed and then regenerate their entire body complete with heart and internal organs, as the journal Current Biology reported.

Doctoral student Mitoh owes her discovery in the lab to a lucky coincidence.

While researching the animals one day, she observed how one of the snails was only moving its head, which had been detached from its body.

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The team even witnessed one slug doing it twice.

"We were surprised to see the head moving just after autotomy," Mitoh writes. Autotomy means the shedding of body parts that are then regenerated.

The heads of relatively young slugs started to feed on algae after just hours and within a week, the regeneration of the heart started.

After about three weeks, the snails had brand new bodies!

The researchers suspect that the animals make use of the photosynthesis of chloroplasts from algae in order to stay alive long enough for regeneration.

The heads of older individuals, on the other hand, did not feed and died after about ten days.

However, the headless bodies continued to move and reacted to touch for several days or even months.

The researchers aren't sure how the sea slugs do it, but Mitoh suspects that there must be stem cell-like cells at the end of the animals' severed necks that allow the body to renew itself.

They are also not certain on why the slugs would do this. One possibility is that it helps the animals remove internal parasites that inhibit their reproduction.

More research is needed to get answers to these questions.