The Lion’s Mane jellyfish (Cyanea capillata) is native to the northern regions of the Arctic, Atlantic and the Pacific Oceans; there are very few Lion’s Mane jellyfish that can be found farther south than 42 degrees north latitude.
The Lion’s Mane jellyfish is the largest and longest jellyfish known and one of the longest animals in general. In 1870, a Lion’s Mane jellyfish was found washed up on the Massachusetts Bay. The bell (body) of the jellyfish had a diameter of 7 feet and 6 inches with tentacles of 120 feet. This Lion’s Mane jellyfish was longer than a Blue Whale, which is frequently considered to be the longest animal in the world. Although this species of jellyfish is able to extend to approximately 8 feet, these jellyfish vary in size. Typically those found in the lower latitudes are smaller in size than those found farther north with an average bell of 20 inches in diameter. The larger specimens may have tentacles that trail as long as 100 feet or more. The tentacles are tremendously sticky and are grouped together in eight clusters. They also are arranged in rows containing 65-150 tentacles in each cluster. The bell of the Lion’s Mane jellyfish is divided into eight lobes that look like an eight-pointed star. An arrangement of tangled, colorful arms spread out from the center of the bell. The arms are much shorter then the thin, silvery tentacles which spread out from the bell’s sub-umbrella. The size of the Lion’s Mane jellyfish also determines the coloration of the specimen. The larger specimens are a brilliant crimson to dark purple where as the smaller specimens tend to be tan or a lighter orange.
The Lion’s Mane jellyfish is commonly known to divers for its painful sting. Though the sting is painful, it is rarely fateful; however, it is toxic and can cause critical burns. Most stings last temporarily and develop local redness. Although the Lion’s Mane jellyfish is possibly dangerous there has only been one person killed by this particular jellyfish. These jellyfish are clearly named for their flamboyant tentacles that resemble a Lion’s Mane.
Being a cold water species the Lion’s Mane jellyfish cannot survive in warmer waters. Though most of its life the jellyfish is pelagic ““ it tends to settle in sheltered, shallow bays near the end of its one-year lifespan. The Lion’s Mane jellyfish acts as a fertile spot for certain species such as butterfish, medusa-fish, shrimp, juvenile prow-fish and harvest-fish providing protection from predators and a reliable source of food. The Lion’s Mane jellyfish has predators of its own including larger fish, seabirds, sea turtles and other jellyfish species. The jellyfish feed mostly on small fish, moon jellyfish, ctenophores, and zooplankton.
Lion’s Mane jellyfish usually remain near the surface of the water, no more than 66 feet deep. The slow pulsations of the creatures move them onward. The jellyfish depend on the current of the ocean whereby the jellyfish can travel significant distances. The Lion’s Mane jellyfish are mainly spotted during late summer and autumn when the jellyfish have grown large in size and the currents of the water begin to pull the jellyfish near the shore. These jellyfish exhibit both asexual reproduction in the polyp stage and sexual reproduction in the medusa stage. There has been speculation and even superstition revolving around prediction of the Lion’s Mane jellyfish population. The Outer Islands (Block Island, Long Island, Nantucket, Martha’s Vineyard, Monomoy, lesser island, and Cape Cod) show the Lion’s Mane jellyfish populations have very predictable seasonal change. Just inches below the surface the sea thermoclines occur usually on the first warm day of spring when numerous young Lion’s Mane jellyfish can be seen; these jellyfish appear in groups of billions and are as small as sand grains. Once the waters proceed to warm, the majority of the jellyfish will die. The few remaining jellyfish that survive will grow slowly; by the end of the summer the average size of the bell is 6 inches. Although the temperature of the water affects the survival of the jellyfish, currents, tides, and wind patterns do not. Given temperature information the bell size can be predicted with great accuracy. In early spring when the water is still cold the young Lion’s Mane jellyfish are too small to cause pain. If Lion’s Mane jellyfish are a concern the best times to swim are May and August.