First published September 6, 2021.
In the summer of 2021, a female smooth-hound shark (Mustelus mustelus) was born at the Cala Gonone Aquarium in Sardinia, Italy, even though her mother had spent about ten years in a tank with no males at all, sharing it with just one other female. Staff named the pup Ispera, a name reported to mean "hope". The leading explanation is parthenogenesis, often called a "virgin birth", and if DNA tests confirm it, Ispera would be the first known case in her species.
Here is what happened, how a shark can reproduce without a mate, and why this rare event matters for shark conservation.
What happened at Cala Gonone
The Italian news agency AGI reported the birth in mid-August 2021, and science outlets including Live Science and ScienceAlert picked it up later that month. The aquarium's marine biologists were puzzled: the mother had arrived years earlier and had shared her habitat only with another female smooth-hound. With no male present for a decade, ordinary mating was ruled out.
The team sent DNA samples from the mother and the pup for analysis, and described parthenogenesis as a hypothesis until those results came back. Ispera was reported to be in good health and expected to live a fairly normal life in captivity.
It is worth correcting one detail that circulated in early retellings: the tank was not full of many long-term female residents. Reports from the aquarium describe the mother living with a single other female.
What parthenogenesis is
Parthenogenesis is reproduction in which an embryo develops from an egg that has not been fertilised by sperm. The word comes from Greek for "virgin" and "origin". Some animals rely on it all the time: several whiptail lizards, for example, are all-female species that reproduce only this way. Many others, including sharks, normally reproduce sexually but can occasionally switch to it when no males are around.
Biologists split the process into types. In apomixis, the egg forms without meiosis (the cell division that halves the chromosome count), so the offspring is essentially a clone. In automixis, meiosis does happen, and the full set of chromosomes is then restored, often by fusing the egg with another product of the same division. The offspring of automixis are not clones; they carry a reshuffled, largely duplicated portion of the mother's genes.
How a shark can have a pup without a male
Sharks studied so far appear to use automixis. When a female produces an egg, she also produces small companion cells called polar bodies, which carry DNA complementary to the egg's. Christine Dudgeon, a shark researcher at the University of Queensland, explained to Live Science that instead of meeting a sperm cell, the egg fuses with one of these polar bodies to make an embryo.
Because all of the pup's DNA comes from the mother, and female sharks carry two X-type sex chromosomes, parthenogenetic shark pups are female. Dudgeon described the process as a form of extreme inbreeding: genetic diversity drops sharply, which can lower a pup's chances of survival. That is why such pups often die young, although some survive, grow up and even reproduce.
Smooth-hounds are viviparous, meaning the young develop inside the mother and are born live rather than hatching from eggs laid on the seabed. A confirmed case in this species would add a live-bearing houndshark to a list that is still short and dominated by aquarium favourites.
Which other animals do it
Demian Chapman, who directs the shark and ray conservation programme at Mote Marine Laboratory & Aquarium in Florida, told Live Science that "about 15 species of sharks and rays are known to do this," and that most species can probably manage it. Across all vertebrates, more than 80 species have been documented reproducing this way, among them reptiles, fish and some birds.
Among sharks, the best-known examples come from carpet sharks such as white-spotted bamboo sharks and zebra sharks, partly because these species are widely kept in aquariums where births can be watched closely. Some individual females have produced parthenogenetic young several times over the years; others switched back to normal reproduction once a male was introduced. Outside sharks, Komodo dragons and several snakes have also had virgin births in captivity.
Why it matters for shark conservation
The common smooth-hound lives in the eastern Atlantic, from the British Isles to South Africa, and throughout the Mediterranean, usually in shallow coastal water up to about 50 metres deep. Adults typically reach 1 to 1.2 metres, and newborns are around 35 cm long. The IUCN Red List classes the species as Endangered.
Chapman has suggested that in the wild, parthenogenesis may act as a last resort for females that cannot find a mate, whether because of isolation, overfishing, disease or habitat change. That makes the phenomenon more than a curiosity. If shark populations thin out, more females may end up in that situation. Their pups could keep a lineage going for a while, but the loss of genetic diversity makes the strategy a stopgap, not a solution. Healthy populations still depend on males and females meeting.
Because the process is so hard to spot in the open ocean, almost everything scientists know about it comes from captive animals. Each documented case, Ispera's included, helps researchers understand how common it might be in the wild.
Common myths and open questions
"A virgin birth means a perfect clone." Not in sharks. Pups produced by automixis share their mother's genes but are not identical copies of her.
"It proves evolution always finds a way." This is a popular line, but it overstates the case. Parthenogenesis is a backup mechanism with real costs, and it does not reliably rescue a species from decline.
"No male means the case is settled." The tank's history makes parthenogenesis the most likely explanation, but genetic testing is what confirms it. Researchers check whether the pup carries any DNA that could not have come from the mother.
What remains open is how often this happens in wild sharks, and whether pups like Ispera can go on to breed. For now, she is a small, healthy reminder that sharks still have surprises left.
Sources: Live Science: Shark in all-female tank has virgin birth; Interesting Engineering: Ispera and the planned DNA tests; Wikipedia: Parthenogenesis; Wikipedia: Common smooth-hound; first reported in English by ScienceAlert.
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