Here's Why Sharks Have Two Penises

By Bryan Lufkin on at

Cartilaginous fishes, like sharks and rays, are blessed with something called “claspers,” dual sperm-releasing tubes jutting from their pelvic fins. Thanks to a recent study, the mystery of the sea critters’ double dongs has been solved.

Researchers at the University of Florida examined the penis-like appendages of male skates in the experiment, whose results were published in the journal Nature Communications last month. What they found was that claspers appear late in male pelvic growth, due to prolonged exposure to the gene that controls skate fin development.

That fin-shaping protein—whose discoverers, clearly twisted Sega fans, named Sonic hedgehog (Shh)—expressed for around four weeks longer in males than females. The team confirmed Shh was vital in the process by injecting carrier beads filled with cyclopamine, an Shh inhibitor, into male embryos. Lo and behold, clasper growth was stunted. Even wilder, pumping female embryos with extra Shh caused those skates to start developing twin penises of their own.

Shh is actually found in animals across the board (including humans) and is responsible for the development of all kinds of body parts, like brains, spinal cords, and limbs. It’s also responsible for ensuring that eye-developing cells split up and form two separate eyes.

Unfortunately, now I won’t be able to stop associating Sonic with shark schlongs.

[Science] Read the full study at Nature Communications.

Image via dconvertini, Creative Commons

Video via BlueWorldTV