A penis that detaches and regrows has been discovered by Japanese researchers. However, the male organ was not found among humans but on a sea slug which is found in the Pacific Ocean.

The scientists were surprised by their discovery while observing the mating behaviour of a species called Chromodoris reticutata, which they collected from shallow coral reefs around Japan.

The team saw the sea slugs mate 31 times which took only a few minutes. After the act, the creatures push away and shed their penises which were left on the floor of the tank where the sea creatures were kept and observed.

The bigger surprise was that after 24 hours, the sea slugs, which are hermaphrodites or possessing both male and female reproductive organs, regenerated their penis and could mate again.

When the researchers examined the animal's anatomy, they found that the sea slugs have a large part of their male organ coiled up in a spiral inside their bodies, which they use to replenish the missing part. The penises were also equipped with spines,

They could copulate three times in a row then need 24 hours to recover for another round of reproduction.

While scientists have observed other animals such as the orb weaving spider, the periwinkle and the land slugs leaving their penises after sex, only the sea slug has the capacity to regenerate that vital part of the anatomy.

The sea slugs are nudibranchs, which means besides possessing both male and female reproductive organs, they could use both at the same time.

"The genital apparatus is on the right hand side of the body. So two nudibranchs come together and one face one way and one faces the other way, with the right side of their bodies touching. The penis from one fits into the female opening of the other, and the penis from that one fits into the female opening of the first one," BBC quoted Bernard Picton, curator of marine invertebrates at the National Museums Northern Ireland.

The study was published in the Biology Letters journal of the Royal Society.

The sea world certainly has interesting sex and copulation behaviour among its creatures such as flatworms that fence with their penises

and the leopard slug which has one of the world's most terrifying male organs.

Among humans, male sex organs become news when they are cut off by their partners, such as an incident in 1993 involving American John Bobbitt, who even capitalised on the incident and eventually became a porn star.

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