Japanese researchers have discovered something unusual about sea slugs. According to the Royal Society Journal Biology Letters, a particular group of sea slugs shed their penes after sex and grow them back again, the Telegraph reports.
"No other animal is known to repeatedly copulate using such 'disposable penes'," researchers said of the red and white shell-less slug, known as Chromodoris reticulata, that can be found in the ocean waters of Southeast Asia.
Once the slug has done the deed, it needs 24-hours to uncoil another grown penis. Researchers say the slug can repeat this behavior at least three times.
"We propose that the tissue at the spiral part of the penis is compressed and undifferentiated, gradually differentiating into the 'next penis'," researchers wrote, adding "It may need approximately a day for the spiral structure to be ready for copulation."
Each slug has both male and female sex organs. When mating the slugs exchange their sperm cells and store them for later insemination.
The slug's penis is also covered in spines, which research say are used to remove the sperm of previous sex partners. The spines are backward-pointing making it difficult to remove the Slug's penis, researchers say this may be the reseaon why the slugs just discards it for another.
"Chromodoris reticulata may compensate for the short-term cost of decreased reproductive opportunities caused by the loss of a penis with the reproductive advantage gained by sperm displacement," researchers wrote.
The report notes that sea slugs aren't the first animals to regenerate a body part but added that very few are willing to let go of a sex organ.
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