A hammerhead shark that gave birth in a Nebraska aquarium reproduced without mating, a genetic analysis shows.
This form of asexual reproduction, called parthenogenesis, has been found in other vertebrate species, including some snakes and lizards. But this is the first time it has been documented in a shark.
Researchers from the Guy Harvey Research Institute at Nova Southeastern University in Florida and Queen's University Belfast found no male DNA in the female baby shark, which was born in December 2001 and died shortly after birth, apparently killed by another fish.
PHOTO: AP
The mother was one of three female bonnetheads, a small hammerhead species, that had been captured in Florida and kept without male sharks for three years in the Henry Doorly Zoo in Omaha, Nebraska.
At the time of the birth, many scientists thought that the female had mated with another species, or that it had used sperm obtained years before. Female sharks are capable of storing sperm, although none have been known to store it as long as these sharks had been isolated.
But through the analysis "it was pretty clear that there was no male contribution," said Mahmood Shivji, director of the Guy Harvey Research Institute and author of a paper on the finding being published online today by the journal Biology Letters.
Instead, the female shark's own genetic material combined during the process of cell division that produces an egg. A cell called the secondary oocyte, which contains half the female chromosomes and normally becomes the egg, fused with another cell called the secondary polar body, which contains the identical genetic material.
Robert Hueter, director of the Center for Shark Research at the Mote Marine Laboratory in Sarasota, Florida, said the finding helped fill a gap in understanding of parthenogenesis, which has been found to occur in most vertebrate lines except mammals and, until now, cartilaginous fishes like sharks.
"These guys have proven their case," Hueter said of the Guy Harvey researchers.
Shivji said that after the bonnethead birth was reported, keepers at the Belle Isle Aquarium in Detroit reported similar virgin births.
READINESS: According to a survey of 2,000 people, 86 percent of Swedes believe the country is worth defending in the event of a military attack Swedes are stocking up on food items in case of war, as more conflict in Europe no longer feels like a distant possibility, and authorities encourage measures to boost readiness. At a civil preparedness fair in southwest Stockholm, 71-year-old Sirkka Petrykowska said that she is taking the prospect of hostilities seriously and preparing as much as she can. “I have bought a camping stove. I have taken a course on preservation in an old-fashioned way, where you can preserve vegetables, meat and fruit that lasts for 30 years without a refrigerator,” Petrykowska said. “I’ve set aside blankets for warmth, I
FRUSTRATIONS: One in seven youths in China and Indonesia are unemployed, and many in the region are stuck in low-productivity jobs, the World Bank said Young people across Asia are struggling to find good jobs, with many stuck in low-productivity work that the World Bank said could strain social stability as frustrations fuel a global wave of youth-led protests. The bank highlighted a persistent gap between younger and more experienced workers across several Asian economies in a regional economic update released yesterday, noting that one in seven young people in China and Indonesia are unemployed. The share of people now vulnerable to falling into poverty is now larger than the middle class in most countries, it said. “The employment rate is generally high, but the young struggle to
ENERGY SHIFT: A report by Ember suggests it is possible for the world to wean off polluting sources of power, such as coal and gas, even as demand for electricity surges Worldwide solar and wind power generation has outpaced electricity demand this year, and for the first time on record, renewable energies combined generated more power than coal, a new analysis said. Global solar generation grew by a record 31 percent in the first half of the year, while wind generation grew 7.7 percent, according to the report by the energy think tank Ember, which was released after midnight yesterday. Solar and wind generation combined grew by more than 400 terawatt hours, which was more than the increase in overall global demand during the same period, it said. The findings suggest it is
‘ARMED CONFLICT’: At least 21 people have died in such US attacks, while experts say the summary killings are illegal even if they target confirmed narcotics traffickers US forces on Friday carried out a strike on an alleged drug-smuggling boat off the coast of Venezuela, killing four people, US Secretary of Defense Pete Hegseth said. The latest strike, which Hegseth announced in a post on X, brings the number of such US attacks to at least four, leaving at least 21 people dead. An accompanying video shared by Hegseth showed a boat speeding across the waves before being engulfed in smoke and flames. “Four male narco-terrorists aboard the vessel were killed,” the Pentagon chief wrote. He said the strike “was conducted in international waters just off the
RSS