Friday, October 17, 2008

Scientists confirm shark's 'virgin birth'!
By Brena Sena
Scientists have confirmed the second case of a 'virgin birth' in a shark. They reported that DNA testing proved that a pup carried by a female Atlantic blacktip skark in the Virginia Aquarium & Marine Science Center contained no genetic material from a male.

The medical mystery began after the death of the Atlantic blacktip skark named Tidbit. No male blacktip sharks were present during her eight years at the aquarium. The 5-foot, 94-pound shark died of stress-related complications related to her unknown pregnancy. The 10-inch shark pup was found during a necropsy (autopsy) of Tidbit. 

Virgin birth has been proven in some bony fish, amphybians, reptiles and birds, and has been suspected among sharks in the wild. The scientists who studied the Virginia and Nebraska sharks said the newly formed pups acquired one set of chromosomes when the mother's chromosomes split during egg development, then united anew. 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 pip, for instance, can be more susceptible to congenital disorders and diseases.

So why would sharks evolve this new way of generating pups? What is the evolutionary benefit when it reduces the pups genetic diversity and makes them more susceptible to disease??

(week 5)


At 7:47 PM, Anonymous Anonymous said...

Wow, ive never heard anything like this! Its really these females have any kind of different behavior that the sexually experienced females?

Mia DiFabbio

At 9:20 PM, Anonymous Anonymous said...

Since the first case confirmed of "virgin birth" in a shark was also at an aquarium center, it is not known that the offspring of an asexual conception may be at a disadvantage for surviving in the wild. Was the first shark the same species as the second case of "virgin birth"? Were the circumstances of the first case of "virgin birth" similar to the blacktip?

There were no male blacktip sharks present during her eight years at the aquarium. So, asexual reproduction was a way to pass on her genes.


At 11:27 PM, Anonymous Anonymous said...

This is fascinating. I wonder if this ever happens in the wild. Granted if there are no male sharks in the wild, I would assume the same thing would occur, but I wonder if it will be something that would take place even with male sharks present? It would seem unlikely because it goes against all logic. If it reduces the offspring's chance of survival and adapting to a changing environment, then ultimately the genes may not get passed on.

At 11:27 PM, Anonymous Anonymous said...

the above 11:27 post is by Katie Cole

At 12:51 PM, Anonymous Anonymous said...

Wow, interesting. It reminds me of how in Jurassic Park, the dinosaurs were all created female to prevent mating, but because the gaps in their DNA were filled in with toad DNA, and some species of toad are able to change their sex, the dinosaurs ended up mating in the wild. I know Jurassic Park is fictional, but I find it really interesting that nature can find away around obstacles. But then again, sharks have been around and evolving since dinosaurs lived on earth.

-Jane de Verges

At 2:31 PM, Blogger bspozio said...

I was curious if it's known how likely it would be for the pup to produce children asexually. I thought this would be an interesting thing to observe

-Benjamin Spozio

At 3:09 PM, Anonymous Anonymous said...

It was amazing to know that virgin birth has actually been proven in some species! How rare is this? Is it due to genetic mutation or other factors? You mentioned that virgin birth is not good for the offspring, is it also bad for the mother, which died of complications related to her unknown pregnancy? I guess it would be evolutionarily convenient for virgin birth to be harmful to both mother and child so that the pregnancy can terminate and no "weak" offspring can survive.

Hanbing Guo

At 7:03 PM, Blogger PWH said...

Virgin birth is very shocking story for me. I did not think this thing could happen. However, it is very interesting. Do you know what kind cause make them to be virginal mother? How long does the virginal birth offspring stay alive? It is very interesting article.

So Jin Lee

At 9:42 PM, Blogger PWH said...

I had no idea that sharks are able to reproduce asexually. I wonder if this is an evolved trait incase females are not able to find males in the wild. I am curious now to how black tip sharks interact with one another. Do black tip sharks rarely encounter one another in the wild? Interesting topic.

-Carlos A. Varela

At 10:03 PM, Anonymous Anonymous said...

I wonder if the hormones and chemicals that are being dumped by humans can cause these asexual births in the wild? Do species reproduce asexually during times of stress? The article makes it seem that this is not that unusual. I'm surprised that more research isn't being done to determine why a female would choose this reproductive strategy when it is disadvantageous to the pup.

Allan Eldridge

At 12:01 AM, Anonymous Anonymous said...

This is incredible!
Do you think this is possible in humans as well?
Although I've never heard of such cases in humans (although it may provide a scientific explanation for the birth of Christ and the Virgin Mary), the theory that some form of sexual contact is necessary for creation is common to the vast majority , if not the entire animal kindgom.
Since it has been spotted in other species as well, is it possible that this can actually happen in humans?

Noam Pelleg (10/17)

At 1:57 PM, Anonymous Anonymous said...

Great post! This asexual reproduction is known as parthenogenesis and, although rare, it is found to occur naturally in some plants, bees, fleas, scorpions and other invertibrates, reptiles, fish, birds, sharks, and other invertibrates. This is different from hermaphroditic species where the animals have both male and female reproductive organs.

Jordan Grinstein

At 9:09 PM, Anonymous Anonymous said...

Great article, I had heard about this and I'm glad you chose it for your blog topic. Scientists know very little about the reproductive behavior of sharks. In some fish species, if there are not enough males around the females will produce more eggs to compensate. I think this could just be the sharks reaction to there being to few or no males, and somehow it has the ability to create a virgin birth. Even though the infant would be genetically inferior, having some sort of offspring might be better then not having any offspring, especially if the species can't find a mate for several years! I think the situation is unique in that the shark was in captivity, but maybe this sort of thing happens in sharks more often then we realize, because we would have no way of knowing about this unless it had happened in captivity. I think it's a great article and it really makes one realize how much we don't know about the life on this planet.

Rachel Carboni


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