Cyanea capillata, commonly known as the lion's mane jellyfish, is distinguished by its reddish-brown bell that can reach up to 2 meters in diameter, with tentacles extending over 30 meters. It thrives in cold, boreal waters, preying on small fish and zooplankton, and serves as both predator and prey within its marine ecosystem.

Cyanea capillata, commonly known as the Lion's Mane Jellyfish, is primarily found in the cold, boreal waters of the Northern Hemisphere. Its geographical distribution includes the North Atlantic and North Pacific Oceans, particularly around the coasts of the United Kingdom, Scandinavia, the eastern seaboard of North America, and parts of the Arctic Ocean.

The Lion's Mane Jellyfish thrives in cold marine environments, typically in waters with temperatures ranging from 0 to 18 degrees Celsius (32 to 64 degrees Fahrenheit). It is often found in coastal regions but can also inhabit the open ocean. The species prefers waters with high salinity and is commonly found at varying depths, from the surface to about 20 meters deep, though it can sometimes be found at greater depths.

Cyanea capillata plays a role as both predator and prey in its ecosystem. It feeds on zooplankton, small fish, and other jellyfish, using its long tentacles equipped with nematocysts to capture prey. It provides a habitat for juvenile fish, which seek refuge among its tentacles. The Lion's Mane Jellyfish is an important part of the marine food web, serving as prey for larger species such as the Leatherback Sea Turtle.