The Lion’s Mane Jellyfish (Cyanea capillata) holds the title of the largest known jellyfish species. It earned its name from the dense, flowing mass of tentacles that trail beneath its bell, giving it the appearance of a lion’s mane. Its striking visual presence establishes its reputation as the most colossal of all gelatinous marine animals.
The Dimensions of the Lion’s Mane Jellyfish
The size of the Lion’s Mane Jellyfish varies significantly based on its geographic location, with the largest specimens inhabiting colder northern waters. The bell, or umbrella, of a typical large individual found in high latitudes can reach a diameter of 2 meters (about 6 feet 7 inches). This bell size makes the jellyfish easily visible in the water.
The true magnitude of the species lies in its tentacles, which are among the longest appendages in the animal kingdom. These slender filaments can trail for distances of 30 meters (about 100 feet) or more. The largest recorded specimen, discovered off the coast of Massachusetts in 1865, had a bell diameter of 2.1 meters (7 feet) and tentacles stretching 36.6 meters (120 feet) long. This tentacle length is roughly the height of a ten-story building.
Anatomy and Structure
The massive body of the Lion’s Mane Jellyfish is divided into three primary components: the bell, the oral arms, and the tentacles. The hemispherical bell has a thick center and a margin scalloped into eight distinct lobes. This bell provides the main structure and propulsion for the animal, moving it weakly through the water column.
The central underside of the bell contains the mouth, surrounded by thick, frilled structures known as oral arms, which are generally about the same length as the bell’s diameter. The tentacles are arranged in eight clusters, with each cluster holding between 70 and 150 individual filaments. Coloration varies with size and age; smaller, younger specimens are often a lighter orange or tan, while the largest adults exhibit deep reddish-purple or crimson hues.
Habitat and Distribution
This jellyfish species is primarily found in the frigid, boreal, and subarctic waters of the Northern Hemisphere. Its distribution spans the Arctic, the North Atlantic Ocean, and the North Pacific Ocean. Cold-water environments, such as the North Sea and the Irish Sea, are where the largest individuals are observed.
The species is pelagic, meaning it lives in the open ocean, though it typically remains near the surface, usually within the top 20 meters (66 feet) of the water column. While they are often spotted during the late summer and autumn, their movements are largely dictated by ocean currents. The jellyfish cannot survive for long in warmer waters, which limits its southern range and keeps it confined to cooler regions.
Interaction with Humans
Contact with the Lion’s Mane Jellyfish can result in a painful sting, a common concern for swimmers and divers. The sting is delivered by microscopic stinging cells called nematocysts, which are coiled capsules located along the tentacles and oral arms. These cells inject venom upon contact, causing a burning sensation, localized pain, and redness.
While the sting is immediately painful and can cause symptoms like muscle cramps or a headache in severe cases, it is rarely fatal to humans. Medical attention is recommended if a large area of the body is affected or if systemic symptoms develop. The nematocysts can still fire and sting even when the jellyfish is dead or its tentacles have broken off and detached in the water.