Autotomy is a phenomenon in which the end parts of the body such as the tail and legs are spontaneously cut off, and it is often regenerated after autotomy.Although some animals have both split bodies completely regenerated, there have been no known examples of animals with complex regimes that survive and regenerate even if they completely lose their body, including the heart.

　Nudibranchs are rare animals that take in the chloroplasts of prey seaweed into somatic cells and use them for photosynthesis.This time, 15 out of 5 indoor-maintained Konohamidorigai and 1 other species of Konohamidorigai collected in the field were autotomized at the neck.The separated body part responded to the stimulus and the heart was moving, but it did not regenerate, and the head of a relatively young individual actively moved around and fed, and the body part including the heart started to regenerate in about a week. , Almost completely regenerated in about 1 weeks.

　Similar autotomy / regeneration was observed in 82 out of 3 copepods parasitized by a copepod (copepoda).Copepods enter the body of sea slugs and suppress spawning, but autotomized copepods completely excrete these copepods and start regenerating the heart in about a week.The 1 unparasitized individuals did not autotomize.

　Researchers speculate that such autotomy takes a long time, so the purpose is not to avoid predation but to eliminate parasites that suppress spawning, and it is speculated that photosynthetic ability is related to the fact that it can be regenerated only from the head. do.In the future, by advancing research on autotomy and regeneration ability, it will be possible to contribute to the fields of regenerative medicine and photosynthesis by animals in the future.

Paper information:[Current Biology] Extreme autotomy and whole-body regeneration in photosynthetic sea slugs