In Vietnam , in the Mekong River, Japanese and Vietnamese scientists have found a new species of fish from the Phallostethidae family, characterized by the fact that both the male and the female have their sexual organs located below the throat , which explains their unique way of mating, face to face. According to its discoverers published in the specialized magazine Zootaxa , Phallostethus cuulong , baptized with the common name of Priapus fish in honor of the rustic Greek god of fertility Priapus, was found for the first time in 2009 and reaches a maximum length of 25 millimeters during the age adult.
Its reproductive system is called the priapium and is made up of modified bones of the pectoral and pelvic fins . In addition to a genital pore and an anal opening, the priapium includes a kind of serrated hook that allows the male to firmly support the female's head during copulation while penetrating it to fertilize the eggs internally. The female deposits the fertilized eggs in the water.
