First Ever Recorded Parthogeesis in a Ray

Parthenogenesis, from the Greek meaning “virgin birth” is an odd quirk of embryonic development that allows female animals of some species to give rise to offspring without a male genetic contribution – usually by a doubling of the egg genome to generate a new embryo with the proper number of chromosomes.

Parthenogenesis has also been documented in at least three shark species, the bonnethead, the blacktip shark,and the zebra shark, and reported in others. Until 2010, however, only a single animal at the time was produced by parthenogenesis, and none survived more than a few days. It was unclear then if elasmobranch parthenotes were as healthy as animals produced from normally fertilized eggs.

In 2001 a bonnethead, a type of small hammerhead shark, was found to have produced a pup, born live on 14 December 2001 in a zoo in a tank that contained no male sharks. 

The pup was thought to have been conceived through parthenogenic means. It was killed by a stingray within days of birth. 

After DNA testing that the reproduction was parthenogenic, there was no male DNA was present in the pup, which was not a twin or clone of her mother, but rather, contained only half of her mother’s DNA. This type of reproduction had been observed in bony fish, but never in cartilaginous fish such as sharks, until this documentation.

In the same year, a female Atlantic blacktip shark in Virginia reproduced via parthenogenesis. On 10 October 2008 scientists confirmed the second case of a virgin birth in a shark.

The Journal of Fish Biology reported a study in which scientists said DNA testing proved that a pup carried by a female Atlantic blacktip shark in the Virginia Aquarium & Marine Science Center contained no genetic material from a male.

In 2002, two white-spotted bamboo sharks were born in Detroit. They hatched 15 weeks after being laid. The births baffled experts as the mother shared an aquarium with only one other shark, which was female. The female bamboo sharks had laid eggs in the past.

A study by Kevin Feldheim of the Pritzker Laboratory for Molecular Systematics and Evolution at the Field Museum in Chicago, and Demian Chapman of the Institute for Ocean Conservation Science at Stony Brook University in New York showed that a white-spotted bamboo shark female gave rise to parthenogenetic offspring that have survived for several years.

Parthenogenetic sharks are therefore not inherently less viable – normal sharks can be produced using only female-contributed chromosomes. It remains unknown whether elasmobranchs actually use parthenogenesis as a method of reproduction in the wild.

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On September 10th, Dutch Burger’s Zoo reported the birth of an eagle ray through parthenogenesis, the first time ever for a ray species! The pup was in good health, but died  of a bacterial infection after three days. Burger’s Zoo has the most succesful breeding programme for eagle rays worldwide.

Hi, my name is Alex and I love Sharks and everything that lives in the sea 🙂

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