In an Australian aquarium, a remarkable female leopard shark amazed scientists by producing a live offspring asexually, three years after being separated from her long-term mate. Scientist have been observing virgin births in vertebrates such as sharks, rays and reptiles. Virgin birth is a reproductive strategy thought to aid survival during periods of isolation.
This is the very first time that a female shark was observed to reproduce asexually after previously mating with a male. It is the third recorded case vertebrate of any species switching its reproductive strategy from sexual to asexual. The only other species that have undergone this unusual biological shift, is the an eagle ray and a boa constrictor, which both were held in isolation.
Before this remarkable event the female leopard shark was previously living with a male partner at the Reef HQ aquarium in Townsville, Queensland between 2006 and 2012. After producing several offspring with her long-term male partner, "Leonie" the female leopard shark was transferred to a separate tank as an effort to scale back its breeding program.
One of Leonie's female pups, Lolly was also transferred to the same tank as her mother. Two years after being separated from male leopard sharks, both Lolly and Leonie laid eggs. Christine Dudgeon is a biologist with the University of Queensland who has been working in collaboration with the Reef HQ aquarium for several years.
According to the CNN, staff at the aquarium noticed that there were embryos in Leonnie's eggs so they attempted to incubate them out of curiosity, although none hatched. After a year, both Lolly and Leonie laid eggs and this time three of Leonie's eggs and two of Lolly's eggs actually emerged into hatchlings.
Dudgeon said, there were two possible explanations for Leonie's eggs hatching. One is sperm storage, this has been documented on several occasions. Sharks are known to store the sperms from male sharks for a long period of time.
The other is parthenogenesis. This has been observed in several sharks, but not with one that had mated previously. In a genetic analysis of Leonie's hatchlings displayed elevated homozygosity. This means that more genes are identical, and they are more likely had been produced asexually than sexually through sperm storage.
Hamish Tristram, a senior aquarist with Reef HQ said this was definitely a surprise, and that Leonie was mating successfully with a male partner for several years, there was nothing much published regarding such large animals switching reproductive strategy so quickly. Tristram said that there are several theories linked to Leonie's sudden unusual behavior. One theory is that in the wild female animals have the tendency to reproduce asexually when no males are available around, just to continue the lineage. However, they are still able to reproduce the traditional way.
According to the Fox News, leopard sharks are known to be endangered, and with this discovery could lead to possible ways on how to conserve the specie. Dudgeon said that he would like to continue observing Leonie's pups, whether or not they could reproduce sexually in their maturity stage. He also wonders, could this happen in the wild, and if so, how often?