Female sharks are doin' it for themselves

[3113]

Study: Female sharks fertilize own eggs

The joint Northern Ireland-U.S. research, being published Wednesday in the Royal Society's peer-reviewed Biology Letter journal, analyzed the DNA of a shark born in 2001 in the Henry Doorly Zoo in Omaha, Neb. The shark was born in a tank with three potential mothers, none of whom had contact with a male hammerhead for at least three years.

Analysis of the baby shark's DNA found no trace of any chromosomal contribution from a male partner. Shark experts said this was the first confirmed case in a shark of parthenogenesis, which is derived from Greek and means "virgin birth."

Asexual reproduction is common in some insect species, rarer in reptiles and fish, and has never been documented in mammals. The list of animals documented as capable of the feat has grown along with the numbers being raised in captivity — but until now, sharks were not considered a likely candidate.

"The findings were really surprising because as far as anyone knew, all sharks reproduced only sexually by a male and female mating, requiring the embryo to get DNA from both parents for full development, just like in mammals," said marine biologist Paulo Prodahl of Queen's University of Belfast, Northern Ireland, a co-author of the report.

Before the study, many shark experts had presumed that the Nebraska birth involved a female shark's well-documented ability to store sperm for a lengthy period of time. Doing this for six months is common, while three years would be exceptional, they agreed. The lack of any paternal DNA in the baby shark ruled out this possibility.

"We were all very skeptical about these reports, about the possibility of a so-called virgin birth in a shark, because sharks have this unusual ability to store sperm for months if not years. So this finding is new and definitely unexpected," said Bob Hueter, director of the Center for Shark Research at the Mote Marine Laboratory in Sarasota, Fla., who wasn't involved in the project.

He noted that sharks have been on Earth longer than other species higher up the evolutionary chain that have also demonstrated this ability, such as lizards and birds.

The report's other co-author, Mahmood Shivji of the Guy Harvey Research Institute in Dania Beach, Fla., said the finding explained growing numbers of reports of mystery, male-free shark births in captivity. Shivji said the research "may have solved a general mystery about shark reproduction," because it suggests that sharks can "switch from a sexual to a non-sexual mode of reproduction." But he said this was not necessarily a positive ability because baby sharks produced only by the mother suffer from "reduced genetic diversity."

 

[neonlyte]

I saw the article this morn my time, three, and immediately thought, 'That's it! I'm coming back as a shark. Sod all this dating business, the chocies and the flowers. The bloody PMT, just in the hope of getting lucky when the moon is in the right quarter and no one has over indulged on booze or food or sunshine. I'm going to be a Hammerhead! Hammerheads Rule.'

 

[Pure]

i see my thread duplicates this. we have similar interests.

here's the link to a somewhat longer article on the suprising findings re hammerheads:

http://www.nytimes.com/2007/05/23/science/23shark.html?_r=1&ref=science&oref=slogin


it appears that to the list of virgin birth higher animals, besides whiptail lizards, and komodo dragons, we must add hammerhead sharks.!

neon, have a look at the 'female only' colonies (whiptails): wanna go?

http://www.alexhuereptiles.com/forums/showthread.php?t=9369


{{I am trying to consolidate things in this thread; hope that's ok}}

 

[neonlyte]

It's a novelty piece. Humans can be made fertile without outside intervention, happily, the need has never arisen. "The last Man Living" might be a worthy Lit Story.

 

[Guest]

Damn, yet another reason they don't need us men.

I could shoot the guy who invented the rabbit vibrator.

Come to think of it, it was probably a woman. I knew we were doomed when MIT started accepting women into the engineering program.