The Lion’s Mane Jellyfish, scientifically known as Cyanea capillata, is the largest known jellyfish species in the world’s oceans. It is recognized by its bell, which ranges from light orange to dark crimson, and the dense curtain of tentacles that inspired its common name. Its sheer physical dimensions and specialized stinging apparatus make it one of the most imposing organisms in the cold northern seas.
Measuring the Largest Known Jellyfish
The size of the Lion’s Mane Jellyfish varies significantly, but the largest specimens dwarf nearly all other jellyfish species. The typical bell, or umbrella, of a mature adult found in northern waters usually measures between 19 inches and 3 feet in diameter. Historical records reveal truly gargantuan dimensions for the largest individuals discovered.
The largest confirmed specimen was recorded in 1865 off the coast of Massachusetts, possessing a bell that spanned about 7 feet across. This diameter is larger than a bicycle wheel and rivals the size of a king-sized mattress. The organism’s tentacles account for the majority of its length.
The tentacles of this record-holding jellyfish were measured at an astonishing 120 feet long. This length makes the Lion’s Mane Jellyfish one of the longest animals on the planet, exceeding the length of the largest known blue whale. The tentacles, which hang in eight distinct clusters, create a massive, sticky net that can cover an area comparable to a basketball court.
Even though these creatures are composed of over 95% water, large specimens can weigh between 200 and 480 pounds. The immense scale allows the jellyfish to efficiently capture prey across a vast area as it drifts through the ocean.
Geographic Distribution and Habitat
This species is primarily confined to the cold, boreal regions of the Arctic, North Atlantic, and North Pacific Oceans. These habitats include the North Sea, the English Channel, and the Gulf of Alaska.
The largest examples of Cyanea capillata are consistently found in the coldest, most northern latitudes, where the growing season is short but the food supply can be abundant. Specimens found in warmer, lower latitudes, such as those that drift south along the East Coast of the United States, are generally much smaller. The difference in size can be dramatic.
These jellyfish spend the majority of their lives in the open ocean, preferring the surface waters but rarely descending below 65 feet. Their movement is primarily dictated by ocean currents, as their gentle pulsations are not powerful enough to swim actively against strong flows. This dependence on currents is why they are often sighted in large numbers, sometimes swarming near coastlines during the late summer and autumn months.
The Lion’s Mane Sting
The trailing tentacles, which give the Lion’s Mane Jellyfish its name, are armed with millions of specialized stinging cells called nematocysts. Each nematocyst contains a coiled, harpoon-like filament that rapidly injects venom upon contact. This biological mechanism is used to paralyze small fish and crustaceans before they are drawn up to the mouth for consumption.
When humans contact the tentacles, the immediate reaction is typically a sharp, burning pain followed by localized redness and swelling. The severity of the sting is largely dependent on the total area of skin contact and the number of nematocysts that successfully fire. While extremely painful, the sting is rarely considered lethal to humans, unlike the venom of some tropical box jellyfish species.
In rare cases involving extensive contact or a sensitive individual, the venom can cause systemic symptoms, which may include muscle cramps, nausea, or headache. Detached tentacles that wash ashore or float freely in the water remain capable of stinging for a significant time. Therefore, contact should be avoided even with pieces of the organism.
Immediate treatment for a Lion’s Mane sting involves rinsing the affected area with vinegar to deactivate any unfired nematocysts still adhering to the skin. Following this initial rinse, applying heat to the area, such as immersing the limb in water heated to approximately 113 degrees Fahrenheit, is recommended to help alleviate the pain. It is important to avoid using freshwater or rubbing the area, as these actions can cause any remaining stinging cells to discharge more venom.