Birds do it, bees do it. Even educated fleas do it, according to Cole Porter’s classic song on the universal nature of sex.
But a baby swell shark born in a Louisiana aquarium that houses only females has flummoxed marine experts and raised the possibility that the species may not require such earthly pleasures to produce offspring.
Yoko, the swell shark pup, hatched on 3 January after an egg was spotted by the US aquarium’s animal husbandry team eight months ago. The egg could have gone undetected for up to two months prior to that, according to the Shreveport aquarium.
The two female sharks present in the tank had not been in contact with a male for more than three years, the team says. This suggests either a process called parthenogenesis, a rare form of asexual reproduction, or delayed fertilisation may have occurred.
A DNA analysis once the pup is big enough for a blood sample to be taken will determine the truth about the mysterious birth, but will take months.
“This situation is incredible and shows the resilience of this species,” said Greg Barrick, the curator of live animals at Shreveport aquarium. “We are very excited in the coming months to confirm whether this was indeed a case of parthenogenesis or if it was delayed fertilisation.”
The baby shark – named after the Native American Chumash people’s word for shark, “onyoko” – was said to be thriving, although the aquarium acknowledged that sharks born though such reproductive events often face significant challenges. Should Yoko’s time with us be short, they said, she will leave an “unforgettable legacy” to the study of shark reproduction and conservation.
If Yoko was indeed born via parthenogenesis, she would join animals such as starfish, deep sea worms and insects capable of such “virgin births”. Laying eggs without mating is much rarer in vertebrates, but it has been seen in zebra sharks, sawfish and a handful of reptiles. The phenomena was first documented in Komodo dragons, the world’s largest reptiles, in 2006, after occuring in two British zoos. Last year, a stingray called Charlotte in an aquarium in North Carolina was found to be pregnant despite not having been in contact with a male for eight years.
While scientists assume vertebrates turn to parthenogenesis when no mates are present, many aspects remain unknown, including why it occurs and what triggers it.
Colin Stevenson, head of education at Crocodiles of the World in Brize Norton, England, a zoo which boasts a male Komodo dragon born by parenthesis to a female in Prague, said: “Komodos are famous for it. They can reproduce normally but every now and again, they pop out a parthenogenetic one. The trick is to work out what kicks it off.”
Article by:Source: Karen McVeigh
