Phallostethus cuulong was swimming quietly in Vietnam's Mekong River, minding its own business, when humans discovered the fish in 2009. And now that researchers have described P. cuulong
[pdf], we can't help violating its privacy by gazing unabashed at its most interesting feature. That feature sits on the throat in the form of a priapium, an organ with as many parts as a Swiss Army knife, most of which contribute to a single function: making as many babies as possible. P. cuulong is the most recently discovered species of 22 known priapiumfish, a family whose males have replaced their penises with muscular priapia, formed from the modified bones of the pectoral and pelvic fins. In addition to an anal opening and a genital pore, the priapium includes a rod and a serrated hook for grabbing a female’s head to keep her throat, and its oviduct opening, close to the genital pore. A firm grip lets the priapium fertilize the female internally without losing too many sperm. Although it sounds uncomfortable, this mating method is actually very effective: Researchers have found female priapiumfish with full oviducts, ensuring that just about all of their eggs get fertilized. Gives a whole new meaning to the term “necking,” doesn’t it? [via Running Ponies
at Scientific American] Image: L.X. Tran
