By Susan Milius
A bristly hermaphroditic sea slug mates employing a use-it-then-lose-it penis, and carries one or two extras for future use, researchers have discovered.
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Some 20 minutes after copulating, the still-stretched-out penis of a Chromodoris reticulata sea slug “just falls off,” says evolutionary biologist Ayami Sekizawa of Osaka City University in Japan. The sea slug then cannot mate for a matter of hours. But when researchers waited 24 hours to offer the slug a second partner, a backup organ segment appeared in place of the discard, she and her colleagues report February 13 in Biology Letters.