|Credit: Tourism & Events Queensland|
...Leonie had been living apart from males for the past few years, so her keepers were surprised when she laid eggs that produced three baby sharks in April 2016. Leonie could be the first shark ever observed to make the switch from sexual to asexual reproduction.
"We thought she could be storing sperm; but when we tested the pups and the possible parent sharks using DNA fingerprinting, we found they only had cells from Leonie," said University of Queensland biologist Christine Dudgeon, who described the case in the journal Scientific Reports Monday (Jan. 16).
Leonie's case marks the first time scientists have seen this type of asexual reproduction —known as parthenogenesis—in the zebra shark (Stegostoma fasciatum).
Parthenogenesis occurs when embryos develop and mature without fertilization by a male's sperm. Rather, an egg progenitor cell that usually gets absorbed by the female's body acts as a surrogate sperm to "fertilize" her egg. This reproduction strategy is more common in plants and invertebrate organisms. However, scientists have been documenting an increasing number of vertebrate species that can have virgin births even when their species normally reproduces sexually. For example, Komodo dragons, the world's largest lizards, have given birth by parthenogenesis. So have wild pit vipers, blacktip sharks, chickens and turkeys...