A new species of fish where the males have their reproductive organs on their head has been discovered in Vietnam’s Mekong Delta.
The Phallostethus cuulong is just 2 centimetres long, and is part of little known group of fish where the males have their reproductive organs on their chin.
The newly discovered specimen is only the 22nd known priapiumfish, which are named after the ancient Greek fertility deity, Priapus, the Daily Mail reported.
They all belong to a family called Phallostethidae and live in south-east Asia.
Researchers said that they are baffled as to why the fish has its sexual organs on its head.
“We don’t know why priapiumfish evolved their peculiar arrangement,” Lynne Parenti of the Smithsonian Institution in Washington, DC, said.
“The fish’s anus is on its priapium, slightly forward from the genital opening. Its guts perform a U-turn to reach it. There’s not much going on at the back of these fish,” Parenti said.
The new species was first discovered in July 2009 by Koichi Shibukawa of the Nagao Natural Environment Foundation in Tokyo, Japan.
He saw one swimming alone in a canal near the Mekong River in Vietnam, and managed to catch it in a net.
Working with colleagues at Can Tho University in Vietnam, he realized it was a new species.