cyanea

Cyanea is a genus of large predatory jellyfish in the family Cyaneidae, within the class Scyphozoa. It includes several species, the best known being Cyanea capillata, the lion's mane jellyfish, one of the largest jellyfish species. Other described species include Cyanea lamarckii, the blue jellyfish, which is comparatively smaller and found in northern European waters.

The medusae of Cyanea have a broad, umbrella-shaped bell with many long, trailing tentacles. In the largest individuals the bell can reach up to about two meters in diameter, and tentacles can extend for tens of meters. Coloration varies from reddish-brown to pale or translucent, often with a dense fringe of long tentacles.

Cyanea species inhabit cold and temperate seas of the Northern Hemisphere, including coastal waters of the Arctic, North Atlantic, and North Pacific. They often occur seasonally in continental shelf regions, where currents concentrate planktonic prey.

Biology and life cycle: Cyanea jellyfish are predators feeding mainly on zooplankton, small fish, and crustaceans. They reproduce sexually; fertilized eggs develop into free-swimming planula larvae that settle as polyps (scyphistoma). Polyps reproduce asexually by strobilation to produce juvenile medusae (ephyrae), which grow into adults.

Human interactions: Stings from Cyanea jellyfish can be painful and occasionally dangerous to humans, depending on species and exposure. There are no widespread conservation concerns specific to the genus, though jellyfish populations respond to environmental changes and climate variability.