Two-headed sharks sound like something out of a B-list horror film, yet scientists are discovering more of them throughout the world.

Some have speculated that the increase of mutants is the result of genetic def.ects caused by overfishing.

The perplexing pattern began in 2008, when Christian Johnson, an Australian fisherman, captured a two-headed blue shark embryo off the coast of Australia. A crew of Floridian fishermen struggled to catch a massive Bull shark in 2013, but when gutting it, they discovered that its u.te.rus contained a two-headed baby.

Because they carry big litters of up to 50 kids at a time in the womb, blue sharks have generated the most two-headed offspring thus far.

More recently, while breeding hundreds of sharks for human-health studies, Spanish researchers discovered a two-headed Atlantic saw tail catshark embryo.

A keen investigator saw it through one of the sharks’ distinctive see-through eggs.

The findings were reported in the Journal of Fish Biology.

The catfish embryo was not your average mutant.

It is the first instance of a two-headed shark being produced by an oviparous shark species (a shark that lays eggs). The researchers gently opened the egg to examine the unusual embryo.

Professor Valentn Sans-Coma, the study’s leader, is doubtful if the embryo would have survived if it had been let to hatch spontaneously.

These em.bryos are unlikely to survive long after hatching, which might explain why two-headed egg-laying sharks have never been discovered. What sparked this recent surge of two-headed shark findings is still unknown to scientists.

While their numbers are increasing, sightings are few and far between, making it impossible for experts to determine what causes the legendary mutation.

Professor Sans-team Coma’s believes that genetic alterations are to blame for their catfish discovery.

Their embryos were cultured in a lab alongside over 800 other specimens, ensuring that they were not exposed to any mutating viruses, chemicals, or radiation.

Rising mutation rates in wild sharks might be caused by a variety of circumstances, including viral infections or pollutants. Overfishing, according to some academics, might be the reason.

As shark populations decline, so does their gene pool, leading to greater in.bre.ed.ing and the dan.ger of passing on catastrophic genetic def.ec.ts.

Nicolas Ehemann, a marine biologist, has discovered the Caribbean Sea’s first two-headed shark.

According to Ehemann, the significant occurrence of two-headed sharks in nature suggests that overfishing is the most likely cause. Ehemann, a master’s student at Mexico’s National Polytechnic Institute, agrees that the smaller shark gene pool caused by fishing would almost certainly result in an increase in birth abnormalities.

This week, researchers in Malaga discovered a two-headed Atlantic sawtail catshark, the first of its type.

The organism was discovered during a study of 797 embryos, and experts from the University of Malaga claim it is the first of its kind.

While prior reports of mutant fish have often been in blue sharks, which carry their progeny in the womb, the discovery is thought to be the first two-headed animal known to be an oviparous shark – those that form within an egg.

However, Dr Felipe Galván-Magaa, a marine biologist at Mexico City’s Instituto Politécnico Nacional, feels that the fear of two-headed sharks is unfounded. He claims that the population of these sharks is not increasing.

Of a truth, the increase in sightings is due to the increasing number of new scientific publications in which to publish.

Dr. Galván-Magaa is not unfamiliar with mutant sharks.

In 2011, a ‘cyclops shark’ with a single working eye was found off the coast of Mexico and brought to his lab.

The def.or.mity was caused by cy.clo.pia, a congenital disorder that affects many animal species, including humans.

Mutated shark specimens are hard to come by, making it difficult for scientists to examine them.

‘I’d want to investigate these phenomena, but it’s not like you throw out a net and occasionally capture two-headed sharks,’ explains Ehemann.

‘It’s arbitrary.’