How Do Jellyfish Eat Without Teeth?

Most jellyfish capture prey using stinging tentacles loaded with cells called cnidocytes. These specialized cells fire tiny harpoons that inject venom into small animals like copepods, plankton, and fish larvae.

Once stunned, the prey gets moved by oral arms toward the mouth—often located at the center of their bell.

Many jellyfish, such as the scyphozoan jellyfish, have four oral arms surrounding a single entry point. This mouth also serves as the exit, meaning jellyfish have a single opening for both food intake and waste expulsion.

The nerve net and small sensory structures help them detect light and motion, guiding them toward dense patches of prey in the water column.

What jellies eat depends on the species. Some prefer tiny creatures like krill, copepods, or even microscopic zooplankton. Others, like the lion's mane jellyfish—one of the largest species—can trap bigger fish or even other jellyfish with their long tentacles.

In short, jellyfish eat almost anything they can sting and swallow. That includes:

A few species, such as the box jellyfish, can even pose a danger to humans. Their venom is potent enough to kill small marine animals—and in rare cases, people.

The upside-down jellyfish flips the script by resting on its bell and using short tentacles to catch prey drifting above. Fried egg jellies, named for their yolk-like appearance, drift passively and trap tiny animals with their tentacles.

Some jellyfish live in symbiosis with algae that provide food via photosynthesis. These jellies survive in nutrient-poor environments by soaking up sunlight.

This shows just how adaptable many jellyfish species are when it comes to finding food.

Jellies are both predators and prey. They feed on zooplankton and other invertebrates, but they’re also on the menu for sea turtles, sharks, and bigger fish. In fact, sea turtles often mistake floating plastic bags for jellyfish—a major threat to their survival.

When jellyfish populations explode in events called jellyfish blooms, they can reshape entire marine ecosystems. Blooms reduce fish populations by competing for the same food and sometimes eating fish eggs and larvae.

Ocean acidification and climate change may be helping jellyfish thrive. Warmer waters can speed up their life cycle and help them outcompete other animals. Jellies often thrive in disrupted marine habitats where more sensitive animals struggle.

Most jellyfish begin life in a polyp stage before budding off into adult forms. Their radial symmetry, simple nerve net, and efficient feeding make them well suited for survival in a changing ocean. That includes deep sea environments with almost no light.

So next time you watch a video of jellyfish pulsing through the sea, remember: Beneath that soft, drifting body is a highly efficient predator, providing food for some animals and outcompeting others.

We created this article in conjunction with AI technology, then made sure it was fact-checked and edited by a HowStuffWorks editor.