India, June 7 -- I f you think the leaf sheep is remarkable, well, another sea slug takes things distinctly further. The Elysia marginata can detach its head from its body and then simply shuffle away, just a blob with tiny antennae, as it regrows itself in its entirety: heart, intestines, reproductive organs and all. In the interim, the slug survives by nibbling on algae. Digestive glands attached to the head, and stem cells in the neck, make the remarkable regeneration possible. This mechanism likely evolved as a way to survive parasitic infections, marine biologists say. In something a bit out of a horror movie, the bodies left behind can live on too, sometimes for months, using chloroplasts, like the leaf sheep, to sustain themselves vi...