The Coral Reefs journal has recently published an astonishing photograph of the birth of a thresher shark, one of the ocean’s most vulnerable species. The picture was taken back in 2013 during a research dive.
In April 2013, Dr. Simon Oliver of the University of Chester and Photographer Attila Kaszo engaged in an expedition off the coast of Philippine Malapascua Island, for the purpose of studying the habits of marine thresher sharks. These types of fish gather at so called “cleaning stations” where they allow smaller fish, like wrasses, to feed off the dead tissue and parasites existent on their bodies. This strange, codependent relationship between sharks and small cleaner fish is known throughout the scientific world and has been thoroughly documented.
But what the two researchers succeeded to capture on their expedition was a photo of a never before documented birth of a thresher shark. The reproductive practices of this shark are poorly known, so it is even bigger of an ironic event that they took the photo completely by accident.
The two researchers, Oliver and Kaszo recollected the incident in an article in Coral Reef. They remember observing a large sized female thresher shark swimming chaotically at the cleaning station, but the great distance between them didn’t allow the two to figure out what was actually going on with her. All they could see from the 15 meters that separated them was that cleaner fish were eating away at her pelvic area. During that time they managed to take the photograph. After a few more minutes the shark left, never to be seen again.
Later, back at their laboratory, they processed the photo and were both amazed at the sight of a baby shark’s head coming out of the shark’s cloaca, the opening for shark’s reproductive organs.
The pelagic thresher sharks are ovoviviparous creatures. This means that they develop their embryos inside eggs that the mother retains inside of her, instead of laying them like most fish species. The female sharks then give live birth to her pup. A female usually gives birth to two pups which are about half the size of her.
The International Union for Conservation of Nature has categorized the thresher shark as a vulnerable species in 2007, along with other species of oceanic sharks.
Image Source: The Washington Post