Taiwanese fishermen have discovered a shark that is both male and female – that is, it has both male and female reproductive organs, an incredible rarity among these impressive fish.
Male sharks have two penises, or penis-like organs known as claspers. So when the 50-centimeter (20-inch) Pacific spadenose shark was caught in the southern Taiwan Strait in January, two claspers were observed and the animal was assumed to be male. However, on internal examination, the shark was found to have both male and female reproductive tracts, as well as gonads with both testicular and ovarian tissue.
An intersex shark might come as a surprise, but hermaphroditism isn’t all that odd in the animal kingdom. Various invertebrates, like worms and snails, contain both male and female sex organs, while the phenomenon occurs in about 21 families of fish, including wrasse, sea bass, and our favorite – the clownfish. In fact, clownfish are able to switch their sex from male to female, so Finding Nemo could have had a very different ending.
Intersexuality isn’t simple, and can vary from species to species. Some animals are protandrous, meaning they can change from male to female, while others are protogynous, meaning they can switch from female to male. Some even turn from male to hermaphrodite. These switches ensure reproduction takes place at times when members of the opposite sex are in short supply. Some intersex species can self-fertilize and produce offspring without a partner, but others still require a mate.
While intersex fish are common, intersex sharks are rather rare. However, a handful of hermaphrodite sharks have indeed been documented. For example, back in 2002, a southern lantern shark possessing both male and female internal sex organs was found off the coast of Tasmania.
So, can these sharks reproduce as either sex? The team from Xiamen University in China believe so. They discovered viable male and female germ cells within the creature, so it's possible it could have functioned as either gender.
However, we still can’t be sure. Scientists have never found an intersex shark carrying a live embryo, nor have captive intersex sharks impregnated females using their male genitalia. Nevertheless, much about shark reproduction still eludes us.
Some sharks have been recorded giving birth to clones. “They can give birth without mating – like virgin birth,” Chris Lowe from California State University told Hakai Magazine. “The question is: why?"
"We just don’t know enough about shark biology to be able to answer those questions," he added.
Sharks usually develop a concrete gender before birth, begging the question: Are intersex sharks random anomalies or do they have an adaptive advantage? Being able to produce offspring without a partner certainly has its benefits, especially when many sharks are quickly swimming towards extinction.