Strange: 'Sea Slug Grows New Penis After Sex'

Experts, who say it needs 24 hours after copulation to unroll another penis, unveil the creature’s bizarre sex life.

The red-and-white sea slug gets rid of its penis after sex and then grows a new one in "extremely peculiar" behaviour, scientists have found.

The animal needs 24 hours between copulation to unroll an internally coiled and compressed juvenile penis to replace the used, external bit, they discovered.

It can even repeat this feat at least three times.

Named chromodoris reticulata in Latin, the human thumb-sized slug - technically a shell-less mollusc - inhabits warm waters in southeast Asia.

It is also an hermaphrodite, meaning it has both male and female sexual organs.

The animals perform dual sexual roles during copulation. They give sperm to a mating partner while simultaneously receiving sperm, which they store for later insemination.

Japanese biologists studied copulation between sea slugs that they had captured during scuba dives and held in a tank.

After each coupling, which lasted between dozens of seconds and a few minutes, every slug discarded its penis - a thread-like organ that it projects from its side into a partner's vagina.

The team also examined the microscopic structure and function of the male organs, observing an internal spiral structure they believe grows into a replacement penis.