The ocean depths conceal creatures of extraordinary size and beauty, and among the most captivating are jellyfish. These gelatinous giants come in a stunning array of shapes and sizes, with some species of jellyfish reaching truly astonishing proportions. While many jellyfish species are small and delicate, some truly earn the title of “biggest jellyfish,” stretching to incredible lengths that could rival even whales.
In this listicle, we dive into the world of the longest jellyfish, exploring six of the most impressive species. From the familiar Lion’s Mane to lesser-known deep-sea dwellers, we’ll unveil the giants that rule the underwater world.
Lion’s Mane Jellyfish (Cyanea capillata)
Length of tentacle: Up to 30.5 meters (100 feet).
Fun Fact: Its tentacles can exceed the length of a Blue Whale, the largest mammal on Earth.
The Lion’s Mane Jellyfish is renowned for its impressive size. It is one of the longest jellyfish species and in the top 3 list of longest animals in the open ocean, with some individuals reaching sizes of up to 8 feet in diameter. The largest known specimen spanned an astonishing 120 feet (36.5 meters) in length, measured from its bell to the bottom of its tentacles. This giant jellyfish gets its name from its resemblance to a lion’s mane, with its long, flowing tentacles and reddish-brown coloration. Its tentacles can extend up to 100 feet long and are covered in stinging cells (nematocysts), used to capture and immobilize prey such as crustaceans, small fishes and zooplankton. The Lion’s Mane Jellyfish is found in the cold waters of the northern hemisphere, including the Arctic and northern Pacific Ocean.
Giant Phantom Jelly (Stygiomedusa gigantea)
Length of tentacle: More than 10 meters (33 feet).
Fun Fact: It is one of the largest invertebrate predators and inhabits every ocean except the Arctic.
The elusive Giant Phantom Jellyfish has been observed only about 100 times in the past century. This massive deep-sea predator is reddish-brown and thrives in the darkness of the ocean’s midnight zone. It is one of the largest invertebrate predators and inhabits every ocean except the Arctic. However, scientists still know very little about this creature. MBARI’s ROVs have provided valuable glimpses into the life of this jellyfish. For example interactions with other deep-sea inhabitants, like the deep-sea fish pelagic brotula, use this jellyfish for shelter.
Nomura’s Jellyfish (Nemopilema nomurai)
Length of tentacle: Over 6 meters (20 feet).
Fun Fact: It has hundreds of microscopic mouths that it uses to feed on plankton.
Nomura’s Jellyfish makes the list of one of the longest jellyfish in the world, with individuals reaching bell sizes of up to 6.6 feet in diameter and weighing 450 pounds. They are predominantly found in the Pacific Ocean, between Japan and China, particularly in the Yellow Sea and East China Sea. Nomura’s Jellyfish is usually pale pink or translucent, with yellow or reddish-pink tentacles. It is known for its voracious appetite and rapid growth, consuming vast amounts of plankton and small fishes, which can have cascading effects on the food chain.
Big Red Jellyfish (Tiburonia granrojo)
Length of tentacle: Up to several meters.
Fun Fact: It differs from other jellies by having thick, fleshy “arms” instead of long, thin tentacles.
During a 1998 survey, MBARI scientists encountered an exceptionally large, crimson jelly, a full meter across, lacking tentacles and sporting finger-like oral arms. This new species, later named Tiburonia granrojo, was formally described with the help of video observations from MBARI’s ROV Tiburon. Since then, it’s been spotted across the Pacific Ocean within the midnight zone, from Baja California to Hawaii to Japan. This highlights how much of the deep sea remains unexplored. Despite a decade of study, many questions remain. Scientists are still trying to find out more about its diet, predators, reproduction, and ecological role.
Sea Nettle Jellyfish (Chrysaora melanaster)
Length of tentacle: Up to 3 meters (10 feet).
Fun Fact: It is the largest jellyfish in the Arctic Ocean.
The Sea Nettle Jellyfish is the largest jellyfish in the Arctic Ocean. Its white, brown, or orange-striped body has 24-32 long orange-red tentacles. It can be found in surface waters down to 100 meters deep, where it preys on a variety of marine life. Its varied diet includes copepods, larvaceans, small fish, large zooplankton, and even other jellyfish. While their lifespan in the Arctic remains a mystery, it’s possible they are short-lived and only survive for a single season.
Barrel Jellyfish (Rhizostoma pulmo)
Length of tentacle: Up to 2 meters (6.5 feet).
Fun Fact: It commonly blooms in late summer and early fall.
The Barrel Jellyfish’s translucent bell, often shaded yellow, pink, or blue, features a violet-fringed edge housing its sense organs. Eight frilly arms, resembling elongated cauliflowers, contain small stinging tentacles that capture zooplankton for its hundreds of tiny mouths. It is found in various locations across the Atlantic Ocean, Mediterranean, and Black Seas. They often wash ashore while feeding on plankton and evading their main predator, the Leatherback Turtle. Sadly, the endangered Leatherback Turtle struggles to survive in an ocean filled with plastic bags that can fatally resemble its favorite jellyfish prey.
Ocean Insights: Hear From Our Experts
By Dr. Rabiah Ryklief
Principal Scientist and Lecturer of Marine Science, with a PhD in Zoology
While climate change threatens countless marine species, jellyfish may actually thrive in warming waters. Researchers from the Alfred Wegener Institute found that rising temperatures and changing conditions could expand the habitats of most Arctic jellyfish species, potentially leading to an "ocean jellification." This shift could significantly impact the marine food web, as jellyfish compete with fish for food and prey on their larvae and eggs, further stressing already vulnerable fish populations. Despite their importance, jellyfish are often overlooked in ecological studies, making this research crucial for understanding the future of our oceans
FAQs
Is a Lion’s Mane jellyfish bigger than a Blue Whale?
No, the Blue Whale is the largest animal on Earth, reaching lengths of up to 100 feet, while the Lion’s Mane jellyfish is considerably smaller in comparison.
How long do jellyfish live?
The lifespan of jellyfish varies depending on the species. Some jellyfish have relatively short lifespans of a few months, while others can live for several years. There are even a few species that are considered immortal, as they can revert back to an earlier stage of their life cycle when faced with unfavorable conditions.
How do jellyfish reproduce?
Reproduction can occur both sexually and asexually. In the medusa stage, jellyfish reproduce sexually through a process called external fertilization. This means that they release sperm and eggs into the water, where fertilization occurs. Some species, however, fertilize eggs internally. After fertilization, the resulting larvae, called planulae, swim freely before settling on the seabed and developing into polyps. These polyps can then reproduce asexually by budding, creating new, tiny medusae that grow into adults.
What is the deadliest jellyfish?
The box jellyfish (Chironex fleckeri) is often considered one of the most deadly jellyfish species. Its venomous tentacles contain toxins that deliver a powerful sting, causeing severe pain, cardiac distress and even death in humans.
