I’ve Been Thunderstruck

There is a very interesting article today at MSNBC.com about virgin births in sharks. Yes, that’s correct…scientiests have found another instance where a pup carried by a female Atlantic blacktip shark contained absolutely no male genetic material at all.

This is the second documented case of parthenogenesis, or asexual reproduction, in sharks. The first instance occured at a zoo in Omaha, NE.

The medical mystery began 16 months ago after the death of the Atlantic blacktip shark named Tidbit at the Virginia Beach aquarium. No male blacktip sharks were present during her eight years at the aquarium.

In May 2007, the 5-foot, 94-pound shark died of stress-related complications related to her unknown pregnancy after undergoing a yearly checkup. The 10-inch shark pup was found during a necropsy of Tidbit, surprising aquarium officials. They initially thought the embryonic pup was either a product of a virgin birth or a cross between the blacktip and a male of another shark species — which has never been documented, Chapman said.

Tidbit’s pup was nearly full term, and likely would have been quickly eaten by “really big sand tiger sharks” that were in the tank, Chapman said in a telephone interview from Florida.

That is what happened to the tiny hammerhead pup in the Omaha case.

“By the time they could realize what they were looking at, something munched the baby,” he said of aquarium workers. The remains of the pup were used for the DNA testing.

Virgin birth has been proven in other species, including some bony fish, amphibians, reptiles and birds.

Absent the chromosomes present in the male sperm, the offspring of an asexual conception have reduced genetic diversity and, the scientists said, may be at a disadvantage for surviving in the wild. A pup, for instance, can be more susceptible to congenital disorders and diseases.

Scientists speculate that such births could become more common if population densities become so low that female sharks have problems finding partners.