anoninnyc
24-05-2007, 08:58 PM
(CBS4) DANIA BEACH Just when scientists think they've got Mother Nature all figured out, she throws them a curveball just to show who's in charge.
Case in point; a female shark on display at a zoo in Omaha, Nebraska gave birth to a pup without the benefit of sperm from a male shark.
A new joint U.S.-Northern Ireland study on the shark's "virgin birth" was published in Wednesday in the Royal Society's Biology Letter journal.
The U.S. research team, led by two scientists from Nova Southeastern University's Oceanographic Center, used DNA from the female sharks and the dead pup to test the unusual phenomenon.
Shark experts say this was the first confirmed case of a sperm-free pregnancy, called parthenogenesis, in sharks.
Mahmood Shivji of the Guy Harvey Research Institute in Dania Beach co-authored the study. He told CBS4s Shomari Stone about the findings.
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."
The three female sharks, which were captured in Florida Bay in 1988, were immature pups themselves when they were delivered to the zoo and placed in a tank that had no male members of the species. In 2001, zoo workers discovered one of the females had given birth, despite the absence of a male. The "virgin birth" pup died within hours, after it was bitten by a stingray in the tank. In examining the pup's DNA, researchers said they found no chromosomal contribution from a male partner.
Asexual reproduction is common in some insect species, and has been known to occur in some reptiles and fish 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 Prodohl of Queen's University of Belfast, Northern Ireland, who wrote the report along with Shivji.
Prodohl said if self-impregnation was occurring in the wild because female sharks cannot find male partners amid rapidly declining shark populations, it would represent "an evolutionary dead end" that would ultimately compromise the survival of the species.
http://cbs4.com/topstories/local_story_143110322.html
Case in point; a female shark on display at a zoo in Omaha, Nebraska gave birth to a pup without the benefit of sperm from a male shark.
A new joint U.S.-Northern Ireland study on the shark's "virgin birth" was published in Wednesday in the Royal Society's Biology Letter journal.
The U.S. research team, led by two scientists from Nova Southeastern University's Oceanographic Center, used DNA from the female sharks and the dead pup to test the unusual phenomenon.
Shark experts say this was the first confirmed case of a sperm-free pregnancy, called parthenogenesis, in sharks.
Mahmood Shivji of the Guy Harvey Research Institute in Dania Beach co-authored the study. He told CBS4s Shomari Stone about the findings.
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."
The three female sharks, which were captured in Florida Bay in 1988, were immature pups themselves when they were delivered to the zoo and placed in a tank that had no male members of the species. In 2001, zoo workers discovered one of the females had given birth, despite the absence of a male. The "virgin birth" pup died within hours, after it was bitten by a stingray in the tank. In examining the pup's DNA, researchers said they found no chromosomal contribution from a male partner.
Asexual reproduction is common in some insect species, and has been known to occur in some reptiles and fish 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 Prodohl of Queen's University of Belfast, Northern Ireland, who wrote the report along with Shivji.
Prodohl said if self-impregnation was occurring in the wild because female sharks cannot find male partners amid rapidly declining shark populations, it would represent "an evolutionary dead end" that would ultimately compromise the survival of the species.
http://cbs4.com/topstories/local_story_143110322.html