A fisherman working off the Florida Keys recently caught a bull
shark, then opened it up to find that it contained two live
fetuses, including one highly unusual one with two heads. The
fishermen gave it to scientists, who wrote about it in an
article.
The scientists, led by C.Michael Wagner of Michigan State
University, said it was the first known case of the phenomenon in
bull sharks, and one of only about a half dozen recorded cases of a
two-headed shark anywhere.
“In and of itself, this single natural history observation does not
tells us anything Earth-shattering about the health of the world’s
oceans or populations of bull sharks,” Wagner told Ocean Views via
e-mail today.
“It’s simply a rarely observed phenomena that we recorded. Yet, it
does capture public attention, and what a great opportunity for
journalists like yourself to shine the light on some interesting
information that does bear on that very important question.” [Does
the two-headed shark teach us anything about the health of the
ocean?]
As further reading, Wagner pointed to the recent Ocean Health
Index published in the journalNature by
Benjamin Halpern and colleagues.
Why Two Heads?
The two-headed bull shark displays a process technically called
“axial bifurcation,” in which the embryo doesn’t finish splitting
into two separate individuals (twins). This mutation has been seen
in other animals, including humans.
According to Wagner’s team, such individuals rarely survive in the
wild, since they are at a big disadvantage when it comes to finding
food and avoiding predators. In this case, the two-headed bull
shark also ended up with a very small body, since so much energy
went into growing two heads.
Wagner said the fishermen who found the animal told him it died
shortly after being removed from its mother. “It likely would not
have survived very long had it been born naturally,” said
Wagner.
Studying such rare organisms may help us better understand
developmental processes, Wagner added.
