A female hammerhead shark that gave birth without sex has put the bite into conventional wisdom about reproduction among large vertebrates, according to research published on Wednesday.
The shark's offspring has no paternal DNA, bemused experts from Northern Ireland and the United States report.
The discovery is the first known case of asexual reproduction in sharks but it also raises concerns about the genetic health of dwindling shark populations, they say.
The investigation was launched after an unexpected birth in an aquarium at the Henry Doorly Zoo in Nebraska in December 2001.
The baby's arrival baffled staff, as none of the three possible mother hammerheads in the tank had been exposed to any male hammerhead for the past three years, after they had been caught as babies off Florida.
The research was carried out by scientists from Queen's University Belfast, the Guy Harvey Research Institute at Nova Southeastern University in Florida and the Henry Doorly Zoo.
The head of the Queen's research team and the study's co-author, Paulo Prodohl, from the School of Biological Sciences, described the findings as 'really surprising.'
"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."
Co-author Mahmood Shivji, who led the Guy Harvey Research Institute team, said the research may have solved a mystery about other species of shark having babies in captivity despite not having contact with males.