A mutant shark may sound like something out of the plot of Jaws or Sharknado, but it’s real. Two-headed sharks do exist and these creatures are popping up more than ever, according to a report by the Miami Herald.
In October, BBC reported that researchers stumbled upon the world’s first recorded instance of an egg holding a two-headed shark embryo. While other shark that give birth to live young have had instances of two-headed offspring in the past, the image of this particular egg astonished people, with some asking if it was simply a hoax.
It was, however, not a hoax. National Geographic recently published an article saying that not only do mutant two-headed sharks exist, there seem to be more and more instances of them on record.
Most of the recorded two-headed sharks are merely embryos or infants, because such creatures are unlikely to survive long in the wild due to their genetic abnormalities. There have been several discoveries of two-headed offspring since 2008. A few years ago in Florida, a fisherman hauled a bull shark whose uterus contained a two-headed fetus. Another fisherman discovered a two-headed blue shark embryo in the Indian Ocean.
More recently, Spanish researchers – led by Valentín Sans-Coma – identified an Atlantic sawtail catshark embryo with two heads. While raising sharks for human-health research in a laboratory, the researchers noticed the unusual embryo in a see-through egg.
This catshark embryo was the first of such specimen known from an oviparous shark species – in other words, a shark that lays eggs.
So what causes the mutation? Two-headed sharks have been few and far between, so it’s difficult to know exactly what lies behind the mutations. Sans-Coma states,
A genetic disorder seems to be the most plausible cause for the two-headed catshark since the embryos were grown in a lab among nearly 800 specimens
To the best of their knowledge, Sans-Coma and colleagues claim that the shark eggs were not exposed to any chemicals, infections or radiation.
Sans-Coma says it’s unknown whether the two-headed shark would have survived in the wild. The rest of their findings were published in the Journal of Fish Biology.
According to National Geographic, the blue shark is the species most likely to produce two-headed offspring because females can carry up to 50 babies at a time. That, combined with overfishing and pollution, has led to the increase in genetic abnormalities as rates of inbreeding increase.
