Coital fanging in a giant cartilaginous fish

Robin and the Honey Badger respond: “The male basking shark has sharp denticles on each of its two phalluses. The largest of these are fivefold longer than any of the denticles that serve as teeth in the mouth of the same species. Because these largest of phallic denticles are the hardest parts of the whole body of this cartilaginous fish they deserve to be called phallic teeth. The vagina of the basking shark is designed accordingly, with a tough pad into which a phallic tooth anchors during copulation. Up to 25 litres per copulation of semen is ejaculated via a deep, scrolled groove in the phallus. Hardening of the phallus – with its numerous small denticles, complex articulating skeleton, and phallic tooth – works in conjunction with propulsion of sea water into the vagina via an inflatable siphon sac up to 50 cm wide. The unusual genital abrasiveness of the basking shark is partly explained by the facts that females breed only once every few years and that the sexes are often separated. There is consequently a need for the female to store bulky semen for long periods and an incentive for the male, prior to his own ejaculation, to remove any sperm stored from a previous mate. This removal is accomplished by flushing the vagina with sea water via one of the paired siphon sacs, a mechanism which partly obviates the need for lubrication and coital thrusting. By anchoring the phallus in the vagina, the phallic tooth allows the male to propel sea water twice in succession, stimulating the female, clearing any previous semen, and injecting his own by hydraulically assisted ejaculation.”