Missouri Snake Gives 'Virgin Birth' for Second Time
After going nearly a decade without any male contact, a female yellow-bellied watersnake has given birth to offspring.
After going nearly a decade without any male contact, a female yellow-bellied water snake in Missouri has given birth to offspring two summers in a row, officials say.
While none of this year's offspring survived, two of the snakes born last summer are healthy and now serving as educational reptiles.
"There is always a high proportion of infertile eggs due to chromosome combination, but a few can be successful and hatch if the mother has a dissimilar sex chromosome," herpetologist Jeff Briggler explains in a news release.
Scientifically known as "parthenogenesis," the so-called 'virgin births' were originally thought to be the product of sperm stored within the female's body for long periods of time. Experts say, however, that this female snake's eight-year dry spell is likely too long for viable sperm to have survived.
While this is the first instance of a yellow-bellied water snake reproducing asexually, parthenogenesis has previously been observed in other species both in the wild and in captivity. The practice is relatively common in lizards and insects, and has also been noted in some species of sharks and snakes.
Mammals are not known to reproduce via parthenogenesis.
The yellow-bellied watersnake had a surprise in store for its nature center handlers.
The world's first known snake has just been discovered in Brazil, according to new research that solves many mysteries about the slithering reptiles. The snake (
), described in the latest issue of the journal Science, is also the first known snake to have four limbs. This strongly suggests that snakes evolved from terrestrial lizards, and not from water-dwelling species, as had been thought before. "The marine hypothesis is dead," senior author Nicholas Longrich of the University of Bath told Discovery News. "It's actually been pretty dead for a while now, but this is really pounding the nails in the coffin. Aquatic snakes evolved from terrestrial snakes -- many, many times." As this image shows,
aka "Four Feet" was a meat-eating predator. It lived in what is now the Crato Formation of Ceará, Brazil, between 146 and 100 million years ago.
If Four Feet could be brought back to life today, "You would be confused, because you would be thinking that this looks like a snake...but it's odd; it shouldn't have feet," lead author David Martill of the University of Portsmouth told Discovery News. He, Longrich, and co-author Helmut Tischlinger believe that the unusual reptile and its kin evolved ever-smaller limbs after their predecessors went through a subterranean phase. During this period of the Early Cretaceous, the animals burrowed underground. "Limbs get in the way if you are burrowing through soft sand," Martill explained. "Much better to 'swim' through leaf litter or sand. As legs got smaller, 'swimming' became more efficient." The scientists further suspect that these undulating movements were pre-adaptations to actual swimming in water.
Four Feet's front limbs were so small that Martill described them as being "pathetic" and "little." While miniscule, the feet seemed to be specialized, as they were broader than those of lizards. As a result, the researchers think the feet helped the snake to seize prey and clasp onto a partner when mating.
Four Feet's head was slightly pointed and slender, suggests its skull. As for its overall appearance, "It looked, well, snaky," Longrich said. "It had the long, slender, serpentine body; it would have had a forked tongue," he continued. "It had the broad belly scales of a snake. This is unique to snakes, and amazingly the fossil actually preserves them." The individual died while young and was only about 8 inches long. The scientists are not sure how big members of the species would have become as adults, but they suspect that adults grew to be over 3 feet long.
The remains of an unknown animal -- possible a lizard -- are remarkably preserved in the gut of the fossilized snake. Based on Four Feet's build, it probably bit its victims and then squeezed them, cutting off their circulation. Organ failure probably followed and then death. The gut contents also indicate that the snake had a feeding strategy similar to today's boa constrictors "in which proportionately large prey are ingested whole," the authors wrote.
The serpentine fossil for Four Feet is extremely well preserved in limestone. It is in such good condition that "soft tissues are also preserved," according to the authors. The snake would have lived in an ecosystem with dinosaurs, they indicated. While this juvenile snake might have eaten small dinosaur eggs, it is possible that adults of the species "could take a hatchling dinosaur," Martill said. Longrich added that 40-50 million years after this snake's lifetime, there were large boa and python-sized snakes that definitely were regular consumers of dinosaur eggs. Remains of snakes are even found in dinosaur nests as a result. Poisonous snakes were not around then, though. They did not become widespread until about 34 million years ago, which was long after non-bird dinosaurs went extinct. The burrowing habits of early snakes might have helped to save them from going the way of the dinos during the major extinction event 65 million years ago.
In addition to lizards like
, Four Feet probably ate salamanders and other small animals, the researchers believe. Both the ancient snake and its prey were "originally from Gondwana, the ancient continent formed by Africa and South America," Longrich said. As he says, "They're sort of a holdover from this lost world."