Weird Nature Sea Creatures Are Growing Two Heads At An Alarming Rate  

Melissa Brinks
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Humanity is becoming increasingly aware that their lives impact the world around them, sometimes negatively. Ocean pollution is a growing concern, as is the impact of global warming and other environmental issues that increase with human proximity. One notable trend that's begun to arise is a potential increase in animals growing two head – a deformity with deadly consequences. 

Pollution hurting sea animals is unfortunately nothing new. Scientists have known about it for years, but it's beginning to have visible effects on the animals that make up marine ecosystems. From the discovery of two headed-shark fetuses to warming ocean temperatures and the ongoing death of coral reefs, people have to acknowledge our part in these changes if in order to have any hope of stopping it. 

The number of two-headed sea creatures being discovered is seemingly increasing, and its possible humanity is to blame. 

The Numbers Of Two-Headed Marine Animals Could Be Increasing


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Photo: Nils Ally/Wikimedia Commons/CC BY 3.0

Scientists believe that the number of two-headed marine animals is increasing, and it could be due to human involvement. Since 2008, multiple high-profile examples of two-headed offspring – AKA conjoined twins or polycephaly – have reached the news, leading more people to be curious about why this appears to be happening more and more frequently.

At least one scientist believes it's not that the number of two-headed creatures is increasing, but rather that there are more scientific journals accepting reports of polycephaly. Regardless, given the limited amount of data, it's important that this matter is further researched. 

Blue Sharks Produce The Most Two-Headed Embryos


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Photo: Mark Conlin/NMFS/Wikimedia Commons

Among the sea animals recorded to have an increase in polycephaly, blue sharks are the most common. This is largely due to the fact that blue sharks can carry up to 50 babies at a time, and with more babies comes more potential for something to go wrong.

It's not necessarily just pure numbers, either. Scientists don't know what exactly is causing this mutation, and it's impossible to tell whether it's dependent on a particular environment or mutation from the parent. Until the cause of the defect can be identified, the solution will likely remain a mystery as well. 

Two-Headed Creatures Rarely Survive Birth


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Photo:  Melissa Wilkins/Flickr/CC BY-NC 2.0

This mutation is a symptom of a problem, but the problem itself is that congenital twins have a very low survival rate. As the number of polycephalic marine creatures increases, so too does the number of young who die long before adulthood.

Even with blue sharks having so many young at the same time, having some die due to birth defects means that there are fewer to survive predation, disease, and other concerns facing young animals. With more and more sharks and other creatures suddenly sporting this mutation, it's important that the cause is discovered before it affects birth rates.

A Genetic Disorder May Be To Blame


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There's not enough data to make a conclusive claim about what is causing the polycephalic sharks – nor whether it's actually on the increase or just more noticeable. One prominent theory is that a genetic disorder is causing the mutations, particularly in the case of the Atlantic sawtail catshark.

This particular polycephalic embryo was grown in a lab, meaning it didn't have exposure to pollution or other environmental factors. This doesn't necessarily mean pollution isn't the underlying cause for the seemingly rising number of wild sharks found to have two heads, but rather that a genetic disorder serves as one potential explanation.