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Losing your body from the neck down can be just another one of life’s annoying, but temporary, setbacks — at least for two kinds of rippling, green-tinged sea slugs.

Heads of young Elysia cf. marginata sea slugs can pull themselves free from their bodies and just keep crawling around while growing a new body, report ecologists at Nara Women’s University in Japan. Within a few hours, some separated heads start nibbling on algae again, Sayaka Mitoh and Yoichi Yusa report March 8 in Current Biology. And within about 20 days, a third of the young sea slugs they watched had grown their bodies back, heart and all.

That’s the first time anyone has reported such dramatic “whole-body” regeneration in any sea slug “as far as we know,” Yusa says.

Other creatures can regenerate, too. In one sense, planarians, the little cross-eyed flatworms that biology students mince up to study regeneration, “are better,” Yusa says. They can regenerate the whole body from multiple cut pieces. Yet their body plan is simpler, and they don’t have hearts.