"Baby thrush shark" born through parthenogenesis is growing

The juvenile thrush shark born through parthenogenesis, which has been on display since February 2023, 2, is growing well and gradually approaching the pattern of an adult fish.

A juvenile thresher shark photographed in September 2024
Exhibition place 3rd floor: "Sharks of the World" tank *Updated November 2024, 11
*Please note that the exhibit location may change or the exhibit may be canceled depending on the condition of the animals.

A distinctive feature of the thresher shark is that its pattern changes as it grows from baby to adult. When it is born, it has clear black and white stripes, but as it ages, this gradually changes to brown spots. In English, it is called the Zebra Shark, as the stripes on its juvenile form resemble those of a zebra. The stripes on the juvenile thresher sharks that have grown healthily in the exhibition tank are gradually becoming fainter.

What the exhibition will look like when it first began in February 2023

DNA analysis of the juvenile thrush shark born at the museum on January 2023, 1 revealed that it was parthenogenetic (reproduction by females only). This was the first time in Japan that parthenogenesis in thrush sharks was revealed through DNA analysis, and that the baby sharks were exhibited.

What it will look like around September 2023

The thrush shark is a type of shark that inhabits the Indian Ocean and the western Pacific Ocean. The baby thrush shark born at our museum was a female, and was 24 cm long when it was born. It will grow to a full length of 2024 cm when measured in August 8. It will continue to grow to nearly 112 m. Adult thrush sharks are on display in the "Sharks of the World" tank on the third floor of the museum. You can compare the patterns and size of the adult thrush sharks with those of the juvenile fish.

Adult tiger shark

It was thought that parthenogenesis in sharks only occurs in females, but this was discovered in an aquarium where males are kept together. This is the third such case to be discovered in the world. In addition to further research into the ecology of sharks, we are working on devising ways to adjust the water temperature and other measures with the aim of sexually reproducing thrush sharks in the aquarium.