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Sea slug has sex, abandons penis, grows new one

AFP-JIJI

Scientists reported Wednesday on the bizarre sex life of a sea slug that discards its penis after copulation, then grows a new one. “No other animal is known to repeatedly copulate using such ‘disposable penes,’ ” Japanese biologists wrote in the Royal Society journal Biology Letters, describing the behavior as “extremely peculiar.”

Dubbed Chromodoris reticulata in Latin, the slug — technically a shell-less mollusk — inhabits warms waters in Southeast Asia.

The critter needs 24 hours between couplings to unroll an internally coiled and compressed juvenile penis to replace the used, external bit, the scientists found. It can repeat this feat at least three times.

The team observed 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 threadlike 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.

Other animals are known to discard parts of their body, such as the gecko, which sheds its tail. Few, though, are willing to part with their penis, the team noted with clinical understatement.