Jellyfish are ancient marine invertebrates found in diverse environments, from shallow coastal waters to the deep sea. They exhibit remarkable diversity in size, from microscopic species to colossal organisms. One species stands out as the largest known jellyfish.
The Lion’s Mane Jellyfish: The Record Holder
The Lion’s Mane Jellyfish (Cyanea capillata) is the largest known species. Its common name describes its appearance, with a dense mass of long, hair-like tentacles reminiscent of a lion’s mane. Its size varies by location, with the largest specimens typically found in colder, more northern waters.
The most substantial recorded Lion’s Mane Jellyfish was found off Massachusetts in 1865. This colossal specimen had a bell diameter of approximately 2.1 meters (7 feet). Its trailing tentacles reached around 36.6 meters (120 feet). To put this into perspective, these tentacles were longer than a blue whale, which is the largest animal on Earth.
The bell of the Lion’s Mane Jellyfish is typically broad and flattened, featuring an eight-lobed or scalloped margin. While juveniles often appear lighter orange or tan, adult specimens can display colors ranging from deep orange to dark crimson or reddish-purple. From the underside of the bell, numerous tentacles hang in eight clusters, with each cluster containing between 70 to 150 tentacles.
The Lion’s Mane Jellyfish primarily inhabits the cold, boreal waters of the Arctic, northern Atlantic, and northern Pacific Oceans. They are also found in the English Channel, Irish Sea, and North Sea, sometimes drifting into the Baltic Sea. These jellyfish are carnivorous predators, using their sticky, stinging tentacles to capture prey such as fish, zooplankton, small crustaceans, and even other jellyfish, including moon jellies. While their sting can be painful to humans, causing irritation, blisters, and muscle cramps, it is rarely life-threatening.
Understanding Jellyfish Size and Other Giants
When discussing the “largest” jellyfish, size can refer to bell diameter or tentacle length. The Lion’s Mane Jellyfish excels in both. Its record-breaking tentacle length makes it one of the longest animals in the ocean.
While the Lion’s Mane holds the record, other jellyfish species also attain considerable sizes. The Nomura’s Jellyfish (Nemopilema nomurai) is another giant, commonly found in the waters of East Asia, particularly between China, Korea, and Japan. This species can grow up to 2 meters (6.6 feet) in diameter and weigh as much as 200 kilograms (440 pounds). Nomura’s Jellyfish can reach this immense size from a grain-of-rice-sized larva in less than a year.
Another notable deep-sea giant is the Giant Phantom Jellyfish (Stygiomedusa gigantea). This species, primarily found in the ocean’s midnight zone, features an umbrella-shaped bell that can exceed 1 meter (3.3 feet) in diameter. Its four ribbon-like oral arms can extend to over 10 meters (33 feet) in length. Unlike many other jellyfish, the Giant Phantom Jellyfish does not possess stinging tentacles, instead using its large, flowing arms to trap and engulf plankton and small fish.