Invasively cloning jellyfish colonizing British Columbia lakes

An invasive Chinese jellyfish species is colonizing the lakes of British Columbia. Scientists from the University of British Columbia noted that these thousands of jellyfish are cloning males of the freshwater species Ryder's Hydra.

"Specimens of the genus Craspedacusta have been reported in 34 freshwater systems since August 1990. These reported locations are generally shallow (<10 m), most often of natural origin, and have a small surface area (<0.1 km²). Until this day, all examined medusae are males," wrote scientists from the University of British Columbia.

Scientists are not certain, but they suspect that over 30 years ago, the small freshwater jellyfish Ryder's Hydra (Craspedacusta sowerbii) from China accidentally ended up in one of the lakes in British Columbia. It likely got there as a result of aquarium water being dumped or was transported by birds.

In the 1990s, the number of jellyfish in British Columbia increased rapidly. They are usually observed from July to October. Researchers have noted that since 2012, jellyfish appearances coincided with abnormal weather conditions in July and August.

In an interview with "The Canadian Press," scientists explained that the discussed jellyfish species thrives in warm waters, especially when the temperature exceeds 27 degrees Celsius. The jellyfish are visible only at a temperature of about 25 degrees Celsius. One of the researchers noted that before reaching the full jellyfish form, they exist as polyps and develop into jellyfish when the water reaches the appropriate temperature. They maintain the jellyfish form only for a few weeks, until the end of September.

Research has shown that all of the jellyfish found in the lakes of British Columbia are genetically identical, which suggests that male jellyfish have the ability to clone themselves.

Freshwater jellyfish are harmless to humans, and people can swim in the lakes where they are present. However, their impact on foreign ecosystems is unknown.

"It is thus of paramount interest to understand its ecology in this warming invaded habitat, allowing for insights into other regions," the researchers emphasized.

In a 2021 article published in the journal "Nature," scientists wrote that the freshwater Asian jellyfish arrived in Europe in the mid-19th century, along with aquatic plants brought to botanical gardens in France and the United Kingdom. This jellyfish has also been found in Australia and Africa. In 1880, Craspedacusta sowerbii was seen outside its natural environment only once; by 1988 already 196 times, and in 2020 as many as 2041 times.