A rare find in the Mediterranean proves that another animal has been born with two heads, and it is not the type that could be slightly beneficial like a two-headed cow that could clear off a field in half the time as a regular cow…no this new discovery is a two-headed shark, proving that two heads are not always better than one.
Scientists in Spain published their findings in October, documenting the first-ever case of a two-headed shark among egg-laying shark species. The research was published in the Journal of Fish Biology, and it describes an Atlantic saw tail catshark embryo.
Information About the Saw Tail CatShark
The Catshark lives only in the western Mediterranean area, at the depths of 330 to 710 meters, and it is near the threat of extinction. As scientists, have studied the fish’s cardiovascular system, the scientists found an embryo that had two heads, each one had its own mouth, and a set of eyes, brain, and gill openings. The embryo had one single intestine but two sets of stomachs and livers.
Anytime that an animal has two heads, it is said to have dicephaly. This is a condition that is relatively rare in the animal kingdom, but it has been seen in various species including snakes and dolphins, as well as people. There was even a two-headed bull shark found by a fisherman off the Florida Keys.
Dicephaly has been seen in other sharks that either bear live young (viviparous) or lay eggs that develop, and then hatch inside the mother (ovoviviparous). But the phenomenon has never been found in true egg-laying sharks (oviparous).
Other Two-Headed Sharks Found in Various Species
This is not the first time that we have seen the evidence of a two-headed shark. Seven other two-headed sharks of various species have been found with two complete heads. Another shark had been found in the past with a duplicated face.
The Spanish team has collected 797 embryos for study of their cardiovascular systems, and only one of the embryos displayed the abnormal feature. This led them to conclude that the incidence of dicephaly in egg-laying sharks is very low.
What Causes Dicephaly in Sharks?
The causes of this condition in animals is not known, but the group of researchers, led by Valentin Sans-Conma of the University of Malaga suspect that genetics are most likely the cause (instead of some strange environmental factor such as radiation).
“We see two-headed sharks occasionally,” says George Burgess, director of the Florida program for shark research at the Florida Museum of Natural History. “It’s an anomaly, caused by a genetic misfire. There are lots of different kinds of genetic misfires, and most don’t make it out of the womb.”
When discussing another discovery of a two-headed shark, biologist C. Michael Wagner of Michigan State University previously told National Geographic that it is important not to jump to conclusions about these rare finds.
“In and of itself, this single natural history observation does not tell us anything earth-shattering about the health of the world’s oceans,” he said.
If the sharks are able to survive until birth, it is a great probability that they will not survive long in the wild. Wagner added,, since they likely have a hard time swimming and finding food.
“There’s a reason you don’t see a lot of sharks with two heads swimming around: they stand out like a sore thumb, so they get eaten,” adds Burgess. “They would have trouble swimming and probably digesting food.”
That is probably good news for swimmers who were afraid to get back into the water due to mutant sharks. But why are we suddenly finding more cases of two-headed sharks in the ocean?
Anecdotal evidence suggests the number of two-headed sharks has been increasing since 2008, when a fisherman discovered a two-headed blue shark embryo in the Indian Ocean, according to NationalGeographic.com.
In 2011, scientists discovered conjoined twins in blue sharks caught in the Gulf of California and in northwestern Mexico, according to the website. In 2013, fishermen off the coast of Florida caught a female bull shark that was pregnant with a two-headed fetus.
Ehemann, a master’s student at the National Polytechnic Institute in Mexico, said he thinks the shark gene pool is shrinking, raising the risk of birth defects such as polycephaly, the condition of having more than one head.
Other possible causes include viral infections, metabolic disorders, and pollution, according to NationalGeographic.com.
The increased number of sightings doesn’t necessarily mean there are more two-headed sharks. Popular Science points out that the increased reports may be because more researchers are studying shark embryos and more journals are publishing their findings.