Who needs males? Female sharks in Italy breed alone: ​​a fascinating phenomenon

A group of Italian researchers reported the first birth by parthenogenesis, that is, without fertilization, of a shark belonging to an endangered species, the Mustelus mustelus.commonly known as dogfish or smooth dogfish.

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“This study represents the first case of facultative parthenogenesis” in this species of shark classified by the International Union for Conservation of Nature (IUCN) as being in danger of extinction, the scientists point out in the study, published this week on the Scientific Reports website.

Researchers from various specialized institutes in Piedmont, Liguria and Aosta Valley They have observed parthenogenesis every year since 2020 in two 18-year-old female sharks Mustelus mustelus, which have been living in a huge aquarium in Sardinia since 2010.

“It is noteworthy that this discovery reveals that parthenogenesis can occur every year in these sharks, alternating between two females, and conclusively excludes long-term sperm storage as a cause,” the researchers stress.

Thus, almost annual production was observed in the absence of males.

So far, there have been three births, in 2020, 2021 and 2023.but only one specimen, the one from 2021, is still alive.

The smooth musola, with an average size of between 1.50 and 2 metres, is mainly threatened by illegal fishing in the Mediterranean and other warm seas.According to estimates cited by researchers, “their population could decline by up to 50% in the coming decades.”

Parthenogenesis, more common among invertebrates than among vertebrates, has not yet been observed in mammals.

Some reptiles, sharks and rays “can modify their adaptive reproductive strategy” depending on environmental circumstances, the report said.

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“Although the mechanisms driving parthenogenesis are unclear, it is suggested that the reduction of the male population could be a determining factor,” the researchers said.

Aquariums in the United States, the United Arab Emirates and Australia have documented this phenomenon in other shark species over the past two decades.

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