A baby smooth-hound shark was born in a tank that only had females, according to the director of an Italian aquarium.
The birth might be the first documented case of parthenogenesis, a form of asexual reproduction where an egg can develop into an embryo without fertilization by sperm.
The baby shark was a surprising discovery in mid-August.
“Our staff arrived at the aquarium in the early morning as usual and when the light of the big pelagic tank (300.000 liters) switched on we immediately realized that there was a new and strange fish between the big amberjacks and groupers,” Flavio Gagliardi, director of the Cala Gonone public aquarium in Sardinia, tells Treehugger.
“We jumped in the tank and caught the newly born shark in order to transfer it in a curatorial tank where proper care could be addressed.”
The baby was born in a tank that housed two female smooth-hound sharks, and no males, for more than a decade.
Researchers at the aquarium sent out DNA samples from the newborn to see whether she is a clone of her mother.
“Currently we do not know how it was possible, however, in order to better understand what happened, we are relying on an Italian research center that is working on carrying out genetic investigations on the two females present in the tank and on the newborn,” Gagliardi says.
“We hypothesize that it is a case of parthenogenesis, because the females in 10 years of residence in the tank have never come into contact with a male.”
Gagliardi says that it may also be possible that when the females were captured in 2010, they had already mated with a male.
“In this case it is conceivable that they kept the sperm for a long time,” he says.
The baby shark was dubbed Ispera.
“Ispera, the name chosen for the little one, in Sardinian means hope and a birth in the Covid era certainly is,” the aquarium posted on Facebook.
Common smooth-hound sharks (Mustelus mustelus) are found in the east Atlantic Ocean, including the Mediterranean Sea. They’re also found in the Canary Islands, Madeira Island and from Angola to South Africa, among other places. They reside in waters over continental shelves and prefer swimming near the bottom.
According to the International Union for Conservation of Nature (IUCN), common smooth-hounds (Mustelus mustelus) are endangered with their population numbers decreasing.
About Parthenogenesis
Parthenogenesis has been documented in many species of insects, fish, reptiles, plants, and birds. It’s a Greek word that means “virgin creation.”
“Parthenogenesis has been shown in several vertebrate species from komodo dragons and whiptail lizards to sharks and chickens and turkeys,” Meg Hoyle, a biologist and owner of Botany Bay Ecotours on Edisto Island, South Carolina, tells Treehugger.
“Genetic testing can prove that no males were part of the reproduction. For some animals it is only used in times of scarcity (like being in a zoo and not having access to a male). For other animals, it is the only way they reproduce. It can increase the population and provide genetic stability for a species.”
Hoyle has witnessed parthenogenesis in lizards in the area around where she lives.
“Six-lined racerunner lizards (Cnemidophorous sexlineatus) are common in hot, open areas from the southeastern U.S. into Mexico. They are the really fast, light colored lizards that usually zip away before you can get a good look at them,” she says.
“These lizards live in the dune system along beaches and live in my yard at Edisto Beach. This species doesn’t just use parthenogenesis when resources are sparse, there are no males in any of the populations. They are female-only lizards and parthenogenesis is the only way they reproduce!”
Parthenogenesis has been confirmed in three other species of sharks: blacktip, bonnethead, and zebra. Researchers are waiting to see if the smooth-hound shark can be added to that list.
“We hope that the researchers we interviewed will shed a clearer light on what has happened than we can,” Gagliardi says.
