This two-headed blue shark fetus was removed from its mother by fisherman Christopher Johnston in 2008, off the coast of Australia. Photograph by Christopher Johnston
We recently wrote about a two-headed bull shark found by fishermen. One of our readers, Christopher Johnston, then sent us an email with photos he had taken on September 27, 2008 of a similarly surprising find: a two-headed blue shark. As far as we know these photos have never been published anywhere before.
As we previously reported, there have been only about a half dozen reported cases of two-headed sharks. The phenomenon arises through conjoined development of twins, the same process that produces what used to be called Siamese twins in people. (See more examples of two-headed animals.)
In January 2011, scientists published a review of two-headed blue sharks in the journal Marine Biodiversity Records. The malformed female blue shark embryos the scientists examined had been found inside a pregnant adult female that had been caught in the Gulf of California off the western coast of Baja California Sur, Mexico.
The underside of the shark fetus. Photograph by CHRISTOPHER JOHNSTON
The researchers, led by Felipe Galván-Magaña, wrote, “Abnormal sharks showed asymmetric bicephaly that could be caused by the high number of embryos found in the uterus of the blue shark, which is the most fecund species of shark in the world. The abnormality probably began during the embryonic development.”
In the case of the two-headed blue shark that appears in the photos in this post, Johnston told us that he found it while working as a longline fisherman in the Indian Ocean. “I can’t remember exactly where we were, somewhere between 200 and 900 miles off West Australia,” Johnston told Ocean Views.
“We pulled up a pregnant blue shark, cut it open, and there was the two-headed one,” he said.
“It was about two-thirds the size of the rest of the pups in length. I put it in the tank on the deck. It swam a little while, but it couldn’t swim properly, it just swam in one spot as if it were on a treadmill. I tried feeding it squid but it wasn’t interested.”
Johnston showed it to the captain and other crew, but he said they were too tired and focused on getting their work done to pay much attention.
After a short while the two-headed pup died, Johnston said. He snapped the photos shown here, then threw it back in the sea.
“I didn’t think it was that special but apparently it is,” Johnston said. “It looked like it had one dorsal fin and one umbilical cord. It had teeth like normal pups.”