By DIVE Staff
A baby shark born in a US aquarium appears to be a rare case of parthogenesis, in which a female animal reproduces without having mated with a male.
The swell shark (Cephaloscyllium ventriosum) pup hatched from an egg at Louisiana’s Shreveport Aquarium in early January. It was laid by one of two females in the aquarium, despite there being no male sharks present in the facility.
The egg was spotted by aquarium staff approximately eight months ago and was closely monitored until it hatched, unaided, on 3 January.
The pup, which has been named Yoko, for ‘onyoko‘, the Native American Chumash word for shark, is being cared for in part of the aquarium that is not open to the public while its progress is monitored.
Parthenogenesis is a form of asexual reproduction in which an embryo develops without having been fertilised by male gametes.
It has been observed in a wide range of species, mostly small invertebrates and insects, but has also been known to occur in amphibians, reptiles and fish – including sharks: between 2016 and 2023, a pair of female hound sharks kept in an Italian aquarium produced four parthenogenetic offspring between them.
The team determined that the two female sharks present in the tank had not been in contact with a male in over 3 years, implying that parthenogenesis was likely.
However, assuming they had some prior contact with a male of the species, the newborn pup could be the product of delayed fertilisation. Female sharks have been known to store a male’s sperm after mating in order to delay the production of an embryo, likely a strategy to improve their offspring’s chance of survival.
The longest case of delayed fertilisation recorded to date is almost four years, when a brownbanded bamboo shark (Chiloscyllium punctatum) produced an egg at the California Academy of Science’s Steinhart Aquarium after 45 months of isolation from male sharks.
DNA testing to determine the cause of conception will be carried out once the pup has reached a suitable size for blood to be taken. Offspring produced through parthenogenesis share identical DNA with the mother – effectively a clone of the parent – while pups conceived through delayed sexual reproduction will be genetically diverse.
‘This situation is incredible and shows the resilience of this species,’ said Greg Barrick, 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 fertilization. It really proves that life can find a way!’
