Sea anemones are a familiar sight in tide pools and coral reefs, with their colorful, flower-like appearance. But what do these seemingly harmless creatures eat? And more interestingly, what animals eat sea anemones?
In this comprehensive guide, we’ll take a close look at the predators and prey of sea anemones, from microscopic plankton to sharks and sea stars.
If you’re short on time, here’s a quick answer: Fish, crabs, shrimp, sea stars, some mollusks like nudibranchs, and microorganisms like plankton and protists are some of the main animals that eat sea anemones.
An Overview of Sea Anemone Diet
Sea Anemones are Predators and Eat Small Fish and Plankton
Sea anemones are carnivorous predators that eat a variety of small marine organisms. Their main diet consists of tiny fish like damselfish and wrasses, as well as plankton like copepods and krill. Anemones catch this prey using their venomous stinging cells called nematocysts, which are located on their tentacles.
When tiny prey brushes up against the anemone’s tentacles, the nematocysts spring open and inject venom into the prey, stunning and killing it so the anemone can eat it.
Some sources estimate that a single anemone may eat 30-40 small fish per day on average. The tentacles of the sea anemone can stretch and sway in the ocean currents to increase the chance of prey making contact.
Some species like the carpet anemones even live symbiotically with anemonefish that attract additional prey towards their tentacles.
Their Tentacles and Stinging Cells Help Catch Prey
Sea anemones have between 50-200 slender tentacles surrounding their mouth and oral disc region. These tentacles contain millions of microscopic nematocysts or stinging capsules that help the sea anemone catch prey.
- The nematocysts lie coiled inside the sea anemone’s tentacles. When potential prey brushes up against a tentacle, the unfurling nematocyst springs open and fires a barbed, venomous harpoon into the prey.
- The venom from nematocysts can paralyze and kill small fish and plankton almost instantly. Larger fish predators avoid the anemone’s tentacles due to this venomous sting.
- Once prey is stunned, the tentacles move the prey into the anemone’s central mouth region for digestion. Waste and indigestible materials are later expelled out of same mouth opening.
Animals that Eat Sea Anemones
Fish
Many species of fish eat sea anemones, including butterfish, pufferfish, filefish, boxfish, and porcupinefish. These fish are able to eat the stinging tentacles of the sea anemone without getting hurt due to special adaptations like thick mucus coats, scales, or spines that protect them.
The clownfish has a symbiotic relationship with certain sea anemones and lives safely among the tentacles, but will also occasional nip at them for food. Some fish like the Porcupinefish will turn the sea anemone over and eat the main body from underneath where there are less stinging tentacles.
Crabs and Shrimp
Crabs and shrimp employ various strategies to be able to eat sea anemones without being stung. Some have tough exoskeletons that protect them, while others numb the tentacles by rubbing them with specialized appendages before consuming them.
The Pea Crab is a small crab that lives commensally among the tentacles of sea anemones, stealing bits of their food while enjoying the protection of the stinging tentacles. Some crabs like Spider Crabs will flip over sea anemones to eat them from the underside.
Sea Stars
Sea stars like the Sunflower Sea Star often prey on sea anemones. Their thick skin protects them from the stings of the tentacles as they engulf the entire anemone in their mouths. Some sea stars like the Striped Sea Star have symbiotic relationships with certain anemones and live among their tentacles while parasitically stealing bits of food from the anemone’s meals.
Nudibranchs
Beautiful sea slugs known as nudibranchs are able to eat sea anemones due to chemical defenses that prevent them from being stung. Special cells called nematocysts in the nudibranch’s skin or digestive system allow them to consume the tentacles and bodies of sea anemones without harm.
Some species like the Clown Nudibranch even collect the stinging cells from the anemones and use them for their own defense!
Other Invertebrates
There are many other marine invertebrates that eat sea anemones to some degree. Snails like the Lettuce Sea Slug scrape off and eat the tentacles and flesh. Hermit crabs may scavenge bits of dead sea anemones that wash up.
Even jellyfish and corals have been known to feed on sea anemones when the opportunity arises! With so many predators, sea anemones have evolved potent stinging cells and adaptations like burrowing in sand or living symbiotically with anemonefish to improve their chances of survival.
Defense Mechanisms of Sea Anemones Against Predators
Their Stinging Cells
Sea anemones have specialized stinging cells called nematocysts that help defend them against predators. These cells contain coiled threads that can spear potential threats. When the nematocysts fire, the threads unfurl and inject toxins into the prey.
The stinging cells are located in the tentacles of the sea anemone and serve as their main line of defense against fish, crabs, and other animals looking for a meal.
Toxins
The toxins injected by the nematocysts come in many forms depending on the sea anemone species. Some common toxins include neurotoxins that paralyze prey and proteolytic enzymes that begin digesting the tissues externally.
The toxins not only help immobilize prey but also deter predators who learn to avoid the painful stings after an encounter with an anemone.
Camouflage and Hiding
Many sea anemones utilize camouflage to avoid being detected by predators. Their column-like bodies and tentacles allow them to blend in with similarly shaped objects like seaweeds and corals. Some species even have striking colors to mimic poisonous or dangerous animals as a warning.
Anemones that live buried in sediment keep only their tentacles exposed while the main body remains hidden and protected.
Cloning and Regeneration
If part of a sea anemone gets damaged or eaten, the animal has an incredible ability to regenerate and heal itself. Some species like the beadlet anemone can reproduce asexually as well by cloning itself and splitting into two separate individuals.
This adaptability makes sea anemones very resilient against predation attempts. Even if a predator gets a piece, the anemone can regrow what was lost and continue thriving after the attack.
Conclusion
In summary, sea anemones have a varied diet of plankton, small fish and other tiny sea creatures. But these predatory creatures also have their fair share of predators like fish, crabs, sea stars, nudibranchs and other invertebrates.
Their stinging tentacles and toxins help defend against predators, along with camouflage and ability to regenerate. Hopefully this guide gave you a comprehensive overview of the predators and prey of fascinating sea anemones!
