The study, led by Michigan State University and appearing in
the Journal of Fish Biology,
confirmed the specimen, found in the Gulf of Mexico April 7, 2011, was a single
shark with two heads, rather than conjoined twins.
There have been other species of sharks, such as blue sharks
and tope sharks, born with two heads. This is the first record of dicephalia in
a bull shark, said Michael Wagner, MSU assistant professor of fisheries and
wildlife, who confirmed the discovery with colleagues at the Florida Keys Community
“This is certainly one of those interesting and rarely
detected phenomena,” Wagner said. “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.”
Creature not alive
The difficulty of finding such oddities is due, in part, to
creatures with abnormalities dying shortly after birth. In this instance, a
fisherman found the two-headed shark when he opened the uterus of an adult
shark. The two-headed shark died shortly thereafter and had little, if any,
chance to survive in the wild, Wagner added.
“You’ll see many more cases of two-headed lizards and
snakes,” he said. “That’s because those organisms are often bred in captivity,
and the breeders are more likely to observe the anomalies.”
The shark was brought to the marine science department at
Florida Keys Community College. From there, it was transported to Michigan
State’s campus for further examination.
Wagner and his team were able to detail the discovery with
magnetic resonance imaging. Without damaging the unique specimen, the MRIs
revealed two distinct heads, hearts and stomachs with the remainder of the body
joining together in back half of the animal to form a single tail.
As part of the published brief, Wagner noted that some may
want to attribute the deformed shark to exposure to pollutants.
“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,” Wagner said. “Making that leap is unwarranted. We simply have no
evidence to support that cause or any other.”
Wagner's research is supported in part by MSU AgBioResearch.