Shark baby born to a female-only tank could be an extremely rare occurrence

Wasim Raza

A shark born to females in an all-female aquarium in Italy may be the first of its kind. An Italian outlet reports that the baby smoothhound shark, named Ispera – that means hope in Sardinian – was born at the Acquario di Cala Gonone in Sardinia, Italy.

Parthenogenesis occurs frequently in zebra sharks (Stegostoma tigrinum). (Image credit: Shutterstock)

This is the first documented case of shark parthenogenesis in its species. Its mother lived in a tank with one other female for 10 years.

Parthenogenesis refers to the phenomenon of developing an embryo from a sperm-less egg.

Sharks, fish, and reptiles are among the species exhibiting this behavior, according to Live Science.

The Florida-based Mote Marine Laboratory & Aquarium’s shark and ray conservation program director, Demian Chapman, says there are about 15 species of sharks and rays that are known to do this.

Despite the fact that sharks may be able to perform these maneuvers, it was difficult to document them in the wild.

Parthenogenesis might be the last resort for females with few mates in low population density, according to Chapman.
This can also occur in captive sharks separated from their male partners for a long period of time, he said.

Parthenogenesis may occur in two different ways, as reported by National Geographic.

One is apomixis, a form of cloning common in plants. Similarly, on record in sharks, there is an automixis that involves a slight alteration of the mother’s genes, which creates offspring that are similar, but not exact copies, of the mother.

“Rather than combining with a sperm cell to produce an embryo, [the egg cell] combines with a polar body, which is essentially a separate cell produced simultaneously with the egg cell with complementary DNA,” said Christine Dudgeon, a biosciences researcher at the University of Queensland. With a single strand of DNA, the polar body looks like a pseudosperm cell.

Dudgeon said the offspring are 100% clones of their mothers. However, they aren’t exactly the same.


Smoothhound sharks (mustelus) have been born as “virgins” in an Italian aquarium – an ecological first for the species.(Image courtesy of Shutterstock)

The reason for this is that sex cells, also known as gametes, have unique genetic combinations that are randomly selected from each parent as they develop – so each shark egg (or polar body) has its own unique genetic profile. Combining the polar body and egg produces a baby shark that is genetically different from its mother. Because parthenogenetic offspring are made from only one gamete, not two, they are more closely related to their mothers than normal babies are, Dudgeon explained.
Sharks can only produce parthenogenic offspring if they are female, and females cannot carry Y chromosomes. It means that the offspring will inherit only her X chromosome, explains Dudgeon.
New York Post reports that Italian aquarium biologists have collected DNA to verify that Ispera was born through parthenogenesis.

Sources:

https://www.businessinsider.com/italy-baby-shark-born-in-virgin-birth-in-sardinia-aquarium-2021-8?amp
https://en.wikipedia.org/wiki/Parthenogenesis

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