WUHAN, Oct. 14 (Xinhua) -- A rare type of freshwater jellyfish, believed to have existed on earth for more than 100 million years, was found in the Danjiangkou Reservoir, central China's Hubei Province.

Gong Dandan, with the Changjiang River Scientific Research Institute of Changjiang Water Resources Commission, was testing water quality at the reservoir when she found the jellyfish last month.

"The jellyfish looked like a dandelion in the water," she said. "I was very excited because I knew it must be something different."

Huang Zhuo, also with the institute, said that only 11 types of freshwater jellyfish had ever been discovered, including nine in China.

"Freshwater jellyfish are very sensitive to the environment, and are critically endangered," Huang said. "They only exist in clean waters."

In recent years, authorities have enhanced efforts to guarantee water quality at the reservoir, the water source of the middle route of the south-to-north water diversion project in China.

Efforts to harness ecological environment near the reservoir and protection of water source have paid off, providing a good environment for the jellyfish, said experts on water environment.