Caroline Morley, online picture researcher
(Image: Charles Smith and Pam Eskridge)
Far from being a miracle, females giving birth without insemination is not uncommon in nature. In addition to many invertebrate species, fatherless offspring have been seen in fish, sharks, birds, lizards and snakes. The phenomenon, known as parthenogenesis, has even been observed in captive individuals of species that can also reproduce sexually.
Now DNA analysis has shown that two wild bisexual species of pit vipers can reproduce asexually. This photo shows one of the species, a female copperhead Agkistrodon contortrix, with one of her parthenogenetic male offspring.
To confirm this behaviour happens in the wild, Warren Booth of North Carolina State University in Raleigh and a team of researchers captured wild pregnant pit vipers and used microsatellite DNA genotyping and litter characteristics to show that the offspring didn't have a father.