Sea slugs remove their own penises after mating, scientists find

A type of sea slug found in the Pacific Ocean is able to remove its own penis after mating and then grow a new one, potentially to increase its chances of mating multiple times, scientists have learned.

In a study, which was published in Royal Society’s journal Biology Letters, Japanese researchers observed Chromodoris reticulata, as the little guys are known, and found that they removed their penises after disengaging from their mating partner.

“The act took between a few seconds and a few minutes, after which the creatures would push away and shed their penises, leaving them on the floor of the tank,” explains BBC News.

The slugs are also capable of storing sperm from several mates. Ayami Sekizawa, a researcher at Osaka City University in Japan, told National Geographic that removing the penis from the mate before shedding it means the slug would still be able to reject other mates’ sperm. “If the sea slug left the penis in the mating partner’s female organ, it could not remove sperm of preceding mates,” Sekizawa told National Geographic.

When researchers studied the discarded penises, they also found that sperm had been entrapped in backward-facing spines on the discarded organs. This could mean the slugs used the spines on their penises to, potentially, remove the sperm belonging other competing slugs.

Once a penis was discarded, the slugs could grow a new penis back in less than 24 hours. But the scientists also found that the animals could only do the deed three times, with the 24-hour waiting periods in between to grow back a new penis.

Another fun fact: the Chromodoris reticulata is a hermaphrodite; it has both male and female sex organs, which can be used simultaneously.

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