Researchers discovered that two species of sea slugs, Elysia cf. marginata and Elysia atroviridis, can regrow their body after cutting off their own head, according to a study published Monday in Current Biology.<br />Some animals like these sacoglossan slugs, also known as sap-sucking sea slugs, can autotomize, which is when an animal sheds a body part voluntarily, said study author Sayaka Mitoh, doctoral student in the department of biological sciences at Nara Women's University in Japan.<br />She said the research team couldn't determine why the slugs shed vital body parts, but some animals do it to remove internal parasites that inhibit their reproduction, Mitoh said.<br />Five of the 15 laboratory-bred young Elysia cf. marginata slugs started to self-decapitate about 226 to 336 days after they hatched. They began feeding on algae within a few hours after losing their body parts and began to regenerate their heart within seven days. After 20 days, the slugs had regenerated their entire body.<br />Three of the 82 Elysia atroviridis slugs decapitated their bodies at the neck. Of those slugs, two of them regenerated their bodies within a week.<br />Not all the slugs were as lucky.<br />Older slugs - the Elysia cf. marginata slugs who were hatched 480 to 520 days prior to self-decapitation - did not feed and died within 10 days.<br />It might seem like a "silly" choice for the older slugs to sever their head from the body if they won't survive, Mitoh said, but the "old ones will die soon anyway and there may be a chance of surviving and regenerating a parasite-free body.<br />Mitoh isn't sure how the slugs can live without some of their vital organs, "but they can live without a heart probably because their heads are small" and can intake oxygen from their body's surface.<br />One of the slugs in the experiment was able to complete the regeneration process twice, but Mitoh said she also is not sure how the slug could do it.<br />More needs to be learned about this phenomenon, both about the species in the experiment and other animals, Mitoh said.
