The Lion’s Mane Jellyfish, Cyanea capillata, is the largest known jellyfish species in the world. This massive invertebrate is characterized by a bell that can reach a diameter of up to eight feet, with trailing tentacles measured at over 120 feet in length. It is predominantly found in the cold, northern waters of the globe, including the Arctic, North Atlantic, and North Pacific Oceans.
The Primary Prey of the Lion’s Mane
The diet of the Lion’s Mane is carnivorous and opportunistic, shifting as the animal increases in size throughout its one-year lifespan. Small individuals begin by consuming microscopic prey such as zooplankton, including copepods and rotifers. As the jellyfish matures and its bell and tentacle mass expand, its prey profile broadens significantly to include larger organisms.
The mainstays of a mature Lion’s Mane diet are small fish, fish larvae, and shrimp, which are easily caught within its massive net of stinging tentacles. They also prey upon other gelatinous creatures, including ctenophores (comb jellies) and smaller scyphozoans, such as Moon Jellies.
How the Jellyfish Captures Its Food
The Lion’s Mane Jellyfish secures its meals through a passive, yet highly effective, form of biological trapping. The bell supports hundreds of long, hair-like tentacles organized into clusters. These tentacles hang down, creating a vast, sticky mesh that acts as a living net spanning a significant volume of water.
Each tentacle is armed with thousands of specialized stinging cells called nematocysts, which are the primary tools for prey capture. When an organism brushes against the tentacles, the nematocysts fire a microscopic, harpoon-like filament loaded with a neurotoxin. This toxin swiftly paralyzes or immobilizes the prey, preventing its escape.
The jellyfish’s hunting strategy also involves the rhythmic pulsation of its bell, which helps circulate water and draw smaller, planktonic organisms into the tentacle curtain. Once the prey is immobilized, the tentacles contract inward towards the central underside of the bell. Specialized structures called oral arms then transport the food to the mouth for ingestion, or begin the digestive process by spreading enzymes over very large prey.
Place in the Marine Ecosystem
Despite its intimidating size and potent sting, the Lion’s Mane Jellyfish is a food source for several specialized marine predators. The Leatherback Sea Turtle is one of the few animals that can tolerate the jellyfish’s stinging cells, making it a primary predator. Some large fish species, such as the Ocean Sunfish, also occasionally consume these jellies, as do certain seabirds.
The predatory nature of C. capillata gives it an important role in controlling populations of small fish and zooplankton. Its consumption of commercially important fish larvae and eggs, however, can bring it into conflict with human fishing interests. Where human activity has reduced the populations of its natural competitors and predators, the Lion’s Mane can thrive, contributing to localized increases in jellyfish swarms.