‘Virgin birth’ is first recorded in a crocodile after a female gave birth in Costa Rica – despite living ALONE for 16 years
- An 18-year-old female American crocodile has given birth to fertilized eggs
- This is despite living alone in a zoo in Costa Rica for the past 16 years
Nature has once again proved that life finds a way, as a female crocodile has given birth to fertilized eggs – despite living alone for the past 16 years.
This is the first time scientists have shown that a crocodile can produce offspring without mating, and they now say dinosaurs could do the same.
Zookeepers discovered that an 18-year-old female American crocodile, a 20-foot apex predator, was guarding a clutch of 14 eggs in her enclosure despite not seeing a male in more than a decade.
It is not entirely uncommon for lone crocodiles to lay unfertilized eggs that are usually discarded; however, researchers were surprised to find that seven of the eggs had actually been fertilized.
Although the eggs failed to hatch after three months of incubation, one was found to contain a fully formed female fetus nearly genetically identical to its mother.
Zookeepers discovered that an 18-year-old female American crocodile, a 20-foot apex predator, was guarding a clutch of 14 eggs in her enclosure despite not seeing a male in more than a decade (stock image)
How does a ‘virgin birth’ work?
Virgin birth is a natural process called facultative parthenogenesis, meaning that a female can produce young without the intervention of a male.
It is extremely rare in nature, although it is found in some other species, notably mayflies, tturkeys, pythons and boa constrictors.
In this particular case, it involved a mechanism called “terminal fusion automixis,” meaning the female fertilizes her own eggs using a genetic by-product called the second polar body.
This means that both parents are the mother and they have two pairs of the maternal DNA.
Wildlife generally does not reproduce this way, but some research now suggests that endangered animals are more likely to do so as mating becomes more difficult.
According to Warren Booth, an associate professor at Virginia Tech who led the study, this discovery “could provide tantalizing insights into the possible reproductive capabilities of extinct archosauric relatives of crocodilians,” including the dinosaurs.
Crocodiles branched off from other dinosaurs about 240 million years ago, but these ancient lizards also share a common ancestor with birds that date back at least 267 million years.
With evidence that crocodiles and birds can both produce young without mating, Booth says this ability is “a trait likely possessed by a distant common ancestor of these genera,” meaning dinosaurs, too, may have exhibited “virgin births.” .
However, “virgin birth” is not the product of divine intervention or sneaky visits by male crocodiles at the zoo, but a natural process called facultative parthenogenesis.
Facultative parthenogenesis is the rare ability to produce offspring without the need for sexual reproduction.
While this could be mistaken for a phenomenon called “long-term storage of female sperm,” in which an animal can produce offspring long after mating, researchers used genetic analysis to prove there was no male involvement whatsoever.
The female embryo was 99.9 percent genetically identical to its mother, showing it had no father.
However, this does not mean that it was a clone.
Although the eggs failed to hatch after three months of incubation, one was found to contain a fully formed female fetus nearly genetically identical to its mother (stock image)
This is the first time scientists have shown that a crocodile can produce offspring without mating, and they now say dinosaurs could do the same
The scientists believe the female crocodile fertilized her own eggs, meaning the offspring contained two copies of its mother’s DNA.
What makes this discovery “particularly interesting,” says Booth, is that crocodile reproduction is very different from any other animal previously known to be capable of facultative parthenogenesis.
Crocodiles lack all sex chromosomes – the X and Y components of our DNA – meaning that the sex of crocodile offspring is determined not by their parents, but by the weather.
In a process known as temperature-dependent sex determination, whether a crocodile becomes male or female depends on the temperature at which the egg is hatched.
Above 99ºF (33º) or below 86ºF (30ºC), 100 percent of crocodile eggs become female, while around 89º (31.5ºC) the offspring are mostly male.
This research has been published in Biology Letters from the Royal Society.
A TIMELINE OF CROCODILE EVOLUTION
250,000,000 BC – Xilousuchus
Three feet tall. 5-10 lbs. Lived in the swamps of East Asia. Eat small animals. Edge of fan-like ‘sails’ on their backs. Split into prehistoric crocodiles and early dinosaurs.
228,000,000 BC – Phytosaurus
Living during the early Jurassic period. Most related to crocodilians. Herbivores. Looked a lot like modern crocodiles – except their nostrils were on the tops of their heads instead of the tops of their snouts.
200,000,000 BC – Erpetosuchus
bipedal. Didn’t resemble modern crocodiles in behavior or body shape except for the shape of their heads.
110,000,000 BC – Sarcosuchus
Middle Cretaceous period. 40 feet long. 10-15 tons. Ate dinosaurs and fish. Lived in the rivers of Africa. Strange protrusion on its snout. Looked and behaved like its modern descendants, but was twice as tall and about 10 times as heavy.
100,000 BC – Stomatosuchus
10 meters long. ten tons. Ate plankton and krill with its high pelican-like jaw.
80,000,000 BC – Beinosuchus
Greek for terrible crocodile. Lived in the rivers of North America. About 33 ft long and 10 tons. They had a 6ft. long skull. Fed on fish, crustaceans and land animals. Evidence in fossils suggests they attacked large North American tyrannosaurs.
70,000,000 BC – Champsosaurus
Five feet long, 25-50 pounds, ate fish and lived in the rivers of North America and Western Europe. Long narrow profile and a tooth-studded muzzle. Survived the Cretaceous-Paleogene extinction event that killed three quarters of the Earth’s plant and animal species, including the dinosaurs.
65,000,000 BC – Cretaceous-Paleogene extinction event
Non-avian dinosaurs were wiped out and more than half of the world’s species were wiped out. This mass extinction paved the way for the emergence of mammals and the appearance of humans.
55,000,000 BC – Crocodylidae (modern crocodile)
The modern crocodile – including the saltwater, Nile and American varieties – spread all over the world. Although it looks prehistoric, it is a highly evolved and complex organism that is a successful predator.
23,000.00 BC – Quinkana
Nine feet tall, 500 pounds. Red meat consumed in forests. Long curved teeth and long legs, as opposed to the short legs of the modern crocodile. These crocodiles are getting smaller due to environmental changes.
4,200,000 BC – Crocodylus thorbjarnarsoni
This is a very close relative of the modern crocodile. Large skull and small raised rim for the eyes. Probably prayed to early humans. Lived in the Turkana Basin in Kenya. Could be the largest known true crocodile.