The Lion’s Mane Jellyfish (Cyanea capillata) is the largest known species of jellyfish, recognized primarily for the extraordinary length of its tentacles. Often called the Arctic red jellyfish or hair jelly, this marine organism is a significant component of the marine ecosystem across the planet’s colder oceans. Understanding this creature requires knowing the frigid habitats where it thrives.
Global Distribution in Northern Waters
The Lion’s Mane Jellyfish is a circumboreal species, spanning the world’s northern oceans in a belt-like distribution. It is primarily confined to the cold, boreal waters of the Arctic, North Atlantic, and North Pacific Oceans across the Northern Hemisphere.
In the North Atlantic, the jellyfish is commonly found in the English Channel, the Irish Sea, the North Sea, and western Scandinavian waters. Its distribution extends along the eastern coast of North America, including the Gulf of Maine, sometimes reaching as far south as the waters below 42°N latitude. It can also be found in the southwestern Baltic Sea, although the low salinity prevents it from breeding successfully there.
Across the Pacific, the Lion’s Mane Jellyfish inhabits areas from Alaska down to Washington, and its presence is noted in Japanese and Chinese waters. While the species is broadly distributed, the largest recorded specimens are consistently found in the coldest, northernmost parts of its range, such as the Arctic Ocean.
Preferred Environmental Conditions
The presence of the Lion’s Mane Jellyfish is directly linked to its preference for specific environmental parameters. This species possesses a strong tolerance for extremely cold water, frequently inhabiting regions where temperatures are near the freezing point of seawater. This adaptation allows it to dominate vast areas of the North Atlantic and North Pacific.
The animal is generally considered a pelagic species, living in the open ocean water column rather than near the bottom. It remains mostly near the surface, typically at depths of no more than 65 feet (20 meters). Its movements are largely dictated by ocean currents because its slow pulsations provide only minimal forward propulsion.
Toward the end of its one-year lifespan, the jellyfish often assembles in sheltered, nearshore areas. This movement makes them more visible to humans, and they are most frequently spotted near coasts during the late summer and autumn.
Notable Physical Characteristics
The Lion’s Mane Jellyfish is named for its distinctive appearance, which resembles a flowing, reddish-yellow mane. The main body, or bell, is broad and flattened, characterized by eight distinct lobes that give it a slightly scalloped margin. While individuals in lower latitudes may have a bell diameter of about 20 inches, the largest Arctic specimens can measure up to 8 feet across.
Hanging from the underside of the bell is a massive cluster of tentacles, the source of the organism’s record-breaking length. These tentacles are organized into eight groups, with each group containing between 70 and 150 individual filaments. The longest recorded tentacles stretched an astonishing 120 feet, making this creature longer than a blue whale.
The coloration varies depending on its size and age. Smaller individuals tend to be lighter, ranging from tan to light orange. As the jellyfish grows larger, its color deepens into rich hues of dark crimson, reddish-purple, or deep orange. The tentacles and frilly oral arms surrounding the central mouth contribute to its dense, flowing appearance.
Ecological Role and Interaction with Humans
The Lion’s Mane Jellyfish acts as a significant predator within the marine food web. Its diet consists mainly of zooplankton, small fish, tiny crustaceans, and other smaller jellyfish and comb jellies. The jellyfish captures its prey by slowly sinking with its tentacles spread wide, creating a vast, sticky net in the water column.
The jellyfish is preyed upon by relatively few marine animals, which include various sea turtles, larger fish, and some seabirds. The stinging cells, called nematocysts, cover the tentacles and deliver a neurotoxin that immobilizes the captured prey. After the prey is stunned, specialized oral arms transport the meal to the central mouth.
Human interaction with the Lion’s Mane Jellyfish usually involves its potent sting. The stinging sensation is caused by the thousands of nematocysts, which are microscopic capsules that fire a barbed, venom-injecting tube upon contact. While the sting is painful and can cause symptoms like rash, swelling, or muscle cramps, it is rarely life-threatening to humans. The stinging cells can remain active and capable of firing even after the jellyfish has died or after a tentacle fragment has broken off and washed ashore.