Aquarium stunned that sharks give birth without mating
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UOZU, Toyama Prefecture–A species of shark that breeds without mating? The wonders of the natural world never cease to amaze.
The process of reproduction from an ovum without fertilization, which also occurs naturally in some plants and invertebrates, is called parthenogenesis.
The Uozu Aquarium here was stunned when two female banded houndsharks gave birth without mating and consulted Kenji Nohara, an associate professor at Tokai University specializing in molecular ecology, for more information on the matter.
The aquarium was intrigued because its tank houses only female sharks. It has since confirmed that the sharks reproduced in parthenogenesis, according to a Sept. 24 announcement by the aquarium.
Nohara said it was the first time parthenogenesis has been confirmed in a banded houndshark anywhere in the world.
The fish are known as bottom feeders that thrive in waters off Japan to the coast of the East China Sea.
Adults grow to about 1.5 meters in length. The sharks are docile and reared in aquariums across the nation.
The Uozu Aquarium said four baby sharks, or pups, were born in 2016 although no male had lived in the tank for more than eight years until then. Three more were born in 2017.
After analyzing the genes of the young sharks, Nohara detected only the mother-oriented gene and judged this to be case of parthenogenesis.
Nohara presented his finding at an annual meeting of the Ichthyological Society of Japan, held at Kochi University on Sept. 21.
Parthenogenesis is known to occur among members of shark and ray families other than the houndshark.
“As a mechanism to ensure species survival, it might more likely occur among more primitive sharks and rays,” Nohara said.
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