The unique specimen was found in the uterus of a captured adult shark caught in the Gulf of Mexico on April 7, 2011. The two-headed, foetal shark died soon afterwards and the body was brought to the marine biology lab at Florida Keys Commmunity College.
There have been a few other dicephalic (two-headed) shark species found over the years (like blue and tope sharks) but this was a first, it seemed, for bullsharks.
Still, some doubted that the creature had true dicephalia, and wondered if it were actually conjoined twins. The specimen was then shipped off to Michigan State University to be examined by a team of biologists led by Michael Wagner, assistant professor of fisheries and wildlife. After conducting an extensive MRI (magnetic resonance imaging) exam — so as not to damage the specimen — Wagner confirmed the discovery with his colleagues at FKCC: it was indeed a two-headed bull shark.
The MRI scans confirmed that the shark has two distinct brains, and, additionally, two complete hearts and stomachs. with the remainder of the body joined together to form a single tail (see photo).
Such dicephalic finds in the wild (verses in capitivity) are fairly rare, as most mutagenic foetuses do not survive long after being born.
Said Wagner: “This is certainly one of those interesting and rarely detected phenomena. It’s good that we have this documented as part of the world’s natural history, but we’d certainly have to find many more before we could draw any conclusions about what caused this.”
Given that the two-headed bull shrk was found in the Gulf not long after the BP/Deepwater Horizon spill, it would seem natural to speculate that pollutants from the spill somehow triggered the deformity. But, one mutated specimen does not equal causal fact.
“Given the timing of the shark’s discovery with the Deepwater Horizon oil spill, I could see how some people may want to jump to conclusions…Making that leap is unwarranted. We simply have no evidence to support that cause or any other.” said Wagner.
Results of the MRI examination are published in the Journal of Fish Biology.
The Bull shark (Carcharhinus leucas), also known as the Zambezi shark, is an aggressive species commonly found world wide in warm, shallow waters and is even found in brackish and fresh water systems (rivers, estuaries) for which it is well-adapted.
Some source material for this post came from the Phys.Org article ‘Scientists confirm first two-headed bull shark’
* SharkDefense is an internationally-recognized and award-winning research organization and think tank focused on shark bycatch reduction. Its core research involves magnetic and electrochemical shark repellent technologies