Scientists were left baffled after they discovered a sea slug that could detach and then re-grow its penis after every mating session.

Japanese researchers were surprised to discover a sea slug with a unique and bizarre mating behavior. The species, scientifically known as Chromodoris reticulata has the capability to throw away and re-grow a penis after every mating session. According to a report by BBC, scientists believe that this is the first of its kind creature with a "disposable penis."

Even without this disposable penis, these creatures are known to have a very complicated sex life as they are known to be "simultaneous hermaphrodites". In layman's terms, they have the sex organs of both a male and a female and can use them both at the same time.

"The general apparatus is on the right hand side of the body. So two nudibranchs come together and one faces one way and one faces the other way, with the right hand side of their bodies touching," said Bernard Picton, curator of marine invertebrates at the National Museums Northern Ireland. "The penis from one fits into the female opening of the other one, and the penis from that one fits into the female opening of the first one, if you see what I mean. They are both donating sperm to the other one,"

However, the discovery of the "disposable penis" has added another layer of complexity to the sex lives of these creatures and Picton says he's never seen anything like this before in his life.

Japanese researchers observed the sexual behavior of these sea slugs and found that they mated 31 times. Each session lasted for a few seconds to a few minutes after which the creature would move away and dispose its penis.

After 24 hours, the sea slug regenerated a new penis and was able to mate again. After closer observation, it was found that the sea slug had a larger portion of its penis inside its body which it would use to re-grow the detached part of the organ.

"They do have very, very complicated biology - and a lot have awfully complicated things in terms of reproduction," Picton said.

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

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