The Blue Jellyfish, (Cyanea lamarckii), also known as the Bluefire Jellyfish, is a species of jellyfish found in the western Pacific around Japan. It is also found in the pelagic zone off the west coast of Scotland, the North Sea and the Irish Sea. It is often commonly found among the more common Lion’s Mane Jellyfish.
This jellyfish has a blue or yellow tone and grows to an average 4 to 8 inches in length, but has been recorded up to 12 inches long. In Scandinavian seas this species rarely grows larger than 6 inches long. It has many stinging tentacles and also has four mouth arms that have many wrinkles and ripples.
Medusae (the young) loosen from mature polyps on the adult sometime between January and March around the British Isles and southern North Sea. This life cycle is similar to that of the Moon Jellyfish.
The specific name — lamarckii — derives from the French naturalist Jean-Baptiste Lamarck (1744-1829).
The taxonomy of this species is not fully agreed upon. Some zoologists suggest that all species within the genus Cyanea should be classified as one. However, this species exists with at least two other distinct taxa in the eastern North Atlantic.