Mysterious Two-Headed Sharks Becoming More Common, No One Knows Why

Two-headed sharks may seem to be a rare phenomenon, but they do exist.

To make matters even more surprising, a growing number of such sharks have been spotted in many years of late; however, scientists are perplexed for their springing up in huge numbers. Last month, scientists came across a shark whose uterus had a two-headed fetus in Spain. The only recognizable two-headed sharks in the past came from species that gave birth to babies straight away, as mentioned by the BBC.

Another fisherman found an embryo of a two-headed blue shark in the Indian Ocean in 2008, reports the National Geographic. A 2011 study found conjoined twins in blue sharks that were discovered in the Gulf of California. Blue sharks have produced the highest number of two-headed embryos since they can carry up to 50 babies at a time, says Felipe Galvan-Magana, leader of the study at the National Polytechnic Institute in Mexico.

In a new study published in the Journal of Fish Biology , researchers were able to recognize an Atlantic sawtail catshark's embryo with two heads. This embryo was not the commonly found two-headed beast and is the first specimen from a shark that lays eggs, also referred to as oviparous sharks. Scientists are now puzzled on figuring out the occurrence of two-headed sharks.

According to Nicolas Ehemann, a student at the National Polytechnic Institute in Mexico, the population of sharks is on a decline mode because of overfishing, increasing the dangers of defects during birth like polycephaly, a condition of having multiple heads. Other notable causes may include metabolic disorders, pollution, and viral infections, according to National Geographic. Another report from Popular Science indicates that this may be seen because more researchers have now started examining shark embryos, with a growing number of journals publishing their discoveries.

Magana has seen other strange sharks too like a "Cyclops" shark, which had a single eye at the front of its head. It was caught in 2011 off Mexico.