Who needs males … or females? If sharks could talk (and thank God they can’t … who wants to hear nonstop bragging about being the top fish in the ocean or how many stupid humans they’ve eaten?), one caught in the Taiwan Strait might answer with a bragging (it’s a shark thing) “Not me!” as it displayed its complete sets of male and female sex organs, making it the first of its species found with them. Is this an aberration, a sign of evolution or a product of humans polluting the oceans?
A report in the latest issue of Hakai Magazine describes the 50 cm (1.65 ft) Pacific spadenose shark (Scoliodon macrorhynchos) which was caught in the southern Taiwan Strait in January 2017.
“Externally, the shark appeared to be an adult male, with a fully developed pair of claspers—penis-like appendages that extend from the pelvic fin. When the shark was examined internally, however, it was found to have a complete pair of ovotestes—gonads that contain both ovarian and testicular tissue—as well as both male and female reproductive tracts.”
This was the first recorded instance of intersex in the Pacific spadenose species, a member of the requiem shark family which may get its name from the French word for shark (requin) or from the fact that they’re responsible for about half of all shark attacks on humans. The shark’s body was taken to China’s Xiamen University where researchers analyzed the shark’s organs and made a second starting discovery – the shark had viable germ cells (a cell containing half the number of chromosomes of a somatic cell and able to unite with one from the opposite sex to form a new individual) of both sexes, which meant both sets of organs had the ability to reproduce.
Sharks have been known to produce offspring asexually, but those cases are typically in females only. The organs on this intersex spadenose are not in the proper position for self-sex. Unfortunately, they don’t carry cellphones so there’s no videos of intersex sharks having sex with normal ones and none of the other rare instances when one has been caught have had an embryo on the female side.
Are intersex and the asexual ‘virgin birth’ related? No one knows and this single find probably won’t answer that question. What about why this happened in the first place? While intersex characteristics in lake fish has been linked to high levels of estrogen in the waters due to the hormone being eliminated in urine and not completely removed by waste water treatment plants, similar studies have not been conducted on sharks.
As always, anomalies of this type are warning signs. There are probably more instances occurring, but sharks are being killed in such huge numbers for food and other purposes that close examination is rarely taking place. Is this their way of surviving? Of fighting back? Should we forget about sharknadoes and start worrying about shark natals?