Why Do Sharks Have Two Penises?

Is it true that sharks have two penises? Why?

Kalvin from Richmond, Ont.

Neat question, Kalvin!

Technically, male sharks don't have penises. What they do have are grooved organs that are used to deposit sperm into the genital duct of sexually receptive female sharks. These organs, called 'claspers', are developed along the inner margin of each pelvic fin (the paired fins located behind a shark's belly). Because the pelvic fins are paired, so are the claspers. That's really all there is to it.

Curiously, although male sharks have two claspers, they only use one at a time. Unfortunately, mating behavior has been observed in only a few species of sharks, but already some basic features of courtship and copulation are clear. When not in use, both claspers lie flat against the undersurface of the body. After communicating its amorous intentions to a sexually receptive female shark through ritualized swimming and gentle 'love nips' along her back or flanks, the male grasps one of her pectoral fins (the wing-like fins located behind the gill slits) in his mouth and arches his body so that his pelvic fins are brought close to hers. If the amorous male happened to 'dock' along the left side of the female, he flexes his right clasper across the mid-line of his body and inserts it into her vent (genital opening). To secure the inserted clasper in place, its tip unfolds in complex, species specific ways  often anchoring by way of one or more spike-like clasper spurs (ouch!). Often, shark mating occurs on the bottom, with the larger female inverted (upside-down), but in some active species  such as the Great White (Carcharodon carcharias) mating apparently occurs right side-up and at or near the surface. In any case, if the male shark happens to dock along the right side of the receptive female, he uses his left clasper.

There is, however, a report from British waters of a pair of Tope Sharks (Galeorhinus galeus) that were captured together, a male and a female locked belly-to-belly by both claspers. So, in case you thought it might be fun to have two penises, you have been warned!