Sea Anemones Facts: Their Tentacles can Sting

Look like beautiful marine flowers, sea anemones are actually terrifying species. They can sting the prey, make them immobile, and eat them. Look at the shocking anemone facts below, you’ll be jaw-dropping.

1. Sea anemones are not plants

Sea anemones (pronunciation: uh-NEM-uh-nee) are also known as the ‘flowers of the sea’. They are named after Anemone flowers because they look like beautiful flowers. Unlike anemones on land, sea anemones are not plants but animals. They are carnivores and have a close relationship with jellyfish and corals. Three of them are classified in the phylum Cnidarian group and have many things in common.

Sea anemones often hook themselves on rough surfaces such as rocks and stones. However, not every anemone does that. Burrowing anemones, on the other hand, hide themselves in mud, sand, or pebbles on the seafloor.

Purple Anemone flowers

They are found in the worldwide ocean, from the cold to the warm water. They can live at a depth of 10.000 meters and more or even in shallow coastal waters. They can even live on the underside of sea ice near Antarctica like this sea anemone – Edwardsiella andrillae. Scientists are still wondering how it can survive in that freezing conditions. In general, sea anemones are commonly found in the Pacific Ocean, Indian, Arctic, Southern, and Atlantic Ocean.

2. They can change their shape

Sea anemones are quite active organisms, although they don’t move much. Their muscular bodies are incredibly versatile, so much that they can turn their stomachs inside out. Furthermore, they can totally fold their oral discs and tentacles within their bodies. Their tentacles also have muscle tissue that is diagonal, vertical, and horizontal. This allows their tentacles to move freely, allowing them to stretch, shrink, twist, and bend.

3. They are powerful carnivores

Sea anemones don’t move much and don’t do much, but they are fearsome predators. Like jellyfish, these sea creatures use their tentacles to sting the prey, making them paralyze to catch. In contrast to their cousin jellyfish, sea anemones don’t move. They wait till their food is close enough to catch. Once the time comes, anemones will extend their tentacles to sting them.

There are specialized stinging cells – cnidocytes – on sea anemone’s tentacles, which allow them to release a strong poison to the prey and make them immobile. And then, they will pull the hapless prey into their mouth and eat them. Furthermore, these tentacles can drag in food fragments floating around. You can clearly on the video below.

Sea anemones eat various prey organisms, including plankton, mollusks, crabs, and fish. Large kinds of sea anemones may, on rare occasions, eat larger animals such as seabirds. Although being a scary predator, anemones still can be eaten by some species of snails, fish (mosshead sculpinsm, butterfly fish), sea slugs, loggerhead turtles and even sea stars.

4. Sea anemones can be parasitic

Although being successful predators in the water, other species like being parasites on other marine creatures. One famous example is the Peachia quinquecapitata which has twelve tentacles.

The anemones are parasitic on particular jellyfish species. When a jellyfish eat the larvae of Peachia quinquecapitata, the larvae will consume the food particles in the jellyfish’s digestive tract first. However, when it’s growing, it will eat jellyfish’s testicles before moving on to other organs. Once the anemone becomes an adult, it will separate from its host and live on the seafloor on its own.

5. Sea anemones can have a symbiotic and mutualistic relationship

  • Symbiotic relationship

Besides getting energy from the prey, anemones of the sea also can get energy from the sun power by collaborating with algae. Since sea anemones cannot photosynthesize on their own, they have to rely on single-celled algae to feed them with photosynthetic products.

These algae live within the cells of the flower of the sea, especially in their tentacles and oral discs. Those parts are upward-facing to receive sunlight. The algae supply oxygen as well as an additional food source for this marine invertebrate. In exchange, the sea anemones protect algae from herbivores and micro-feeders.

  • Mutualistic relationship

Sea anemones and clownfish

If you watched the Finding Nemo film by Pixar in 2003, you knew that Nemo and his father live in sea anemones. perhaps you don’t know that this is a mutualistic relationship between clownfish (or anemonefish) and the sea anemone. This means that both of them benefit from each other.

With stinging tentacles, sea anemones can protect clownfish and give them a safe home to stay. Clownfish can also eat the leftovers and dead tentacles of anemones. In return, clownfish will prevent “the host” from parasites and potential predators.

Sea Anemone and clownfish family

But how can clownfish live in there without being stung? There are several theories for why sea anemones are unable to harm the clownfish. Some say that clownfish’s mucus coating makes them invisible to the stinging cells of sea anemones. The others suggest this kind of fish developed resistance to the toxins of anemones tentacles.

Clownfish feces can provide nitrogen for the algae living within the cell of sea anemones. As a result, this can help the sea anemones develop and regenerate. The vibrant colors of clownfish may also attract tiny fish for sea anemones to eat. They can also maintain a continuous flow of water all around the tentacles. This can make anemones grow bigger as well as the clownfish’s respiration.

Boxer crabs

Boxer crabs hold sea anemones on their two claws, which makes them known as pom-pom crabs. This adds another layer of protection for these little crabs. The sea anemones, in return, have easier access to food since they are carried around.

When the boxer crabs lose one anemone in one of their claws, they will cut the left anemone in half. The two parts can recover and become two new sea anemones because they can reproduce like that.

Similarly, some hermit crabs protect themselves by carrying sea anemones in their shells. When they move from their old shells to new ones, the anemones are transferred to the new shells. You can see this kind of relationship most in the sea anemone Adamsia palliata and hermit crab Eupagurus prideauxi. They are always together.

6. They can walk and swim

Most sea anemones have 3 parts: a cylindrical body with radial symmetry, a pedal disc (or foot), and a central mouth surrounded by venom tentacles on the top. To attach to certain surfaces, they use their “feet” or their pedal discs. Once stuck on a surface, they barely move and remain in the same place for the rest of their lives.

However, when the conditions are unsuitable to survive, they will move with their feet. Sea anemones can walk or float, but their movements are so slow that you can’t see them with your naked eye. Some can release from surfaces and let currents take them to another location.

The sea onion (Paranthus rapiformis) can even transform into a spherical shape and be rolled away by currents. Other species, Gonactinia prolifera, and Stomphia coccinea, can swim by themselves to new places s by their tentacles or their bodies.

7. They can reproduce sexually and asexually

Like the cousin jellyfish, sea anemones can reproduce sexually as well as asexually. For sexual reproduction, the male will shoot their sperm into the water. This causes the females to produce their eggs, and fertilization takes place in the water or inside the female bodies. The egg will become larvae, the larvae will become planktonic or free-floating organisms before they settle on the seafloor. However, they live their entire lives in a polyp stage and do not go through a medusa phase like the jellies.

Some sea anemones keep their sex fixed and separated, while the other species are hermaphrodites and change their sex at some time in their development. Brooding anemone (Epiactis prolifera) is a typical example.

Sea anemone reproduce by budding

To reproduce asexually, sea anemones will separate themselves or clone themselves. The offspring produced by this process share the same DNA as the parent. They can also asexually reproduce as the way plants do, by fragment, binary fission, or budding. Some species are even viviparous, such as Beadlet Anemones (Actinia equina which are discovered off the shore of British. They give birth to live offspring by spitting them out of their mouths (after internal fertilization).

Sea anemones prefer to take things slowly; they develop slowly, they move slowly and they live very long. According to reports, certain species can live so much longer. The magnificent sea anemone (Heteractis magnifica) has been reported to live for more than 80 years.

8. They have territorial behavior

Different groups of sea anemones can compete over territories. Let’s take aggregating anemone (Anthopleura elegantissima) as an example. These species asexually reproduce by cloning and the members of their group are genetically identical to each other. When one group is too close to another which don’t have the same DNA, they will fight for territory. This usually happens to the smaller species; the bigger anemones are more solitary.

The war will begin if the anemones release secondary defense tentacles and participate in such seriously slow and violent fighting. Their thicker secondary tentacles will rise from behind their primary ones and begin attacking the opponent. The flight will last until one team earn a favorable place on the seafloor. However, both teams can lose if they suffer too much loss.

9. Similar features to jellies

Belong to the same group, sea anemones and jellyfish have many things in common:

– Mouth and anus are in the same place, which means that their mouths are also their anus. More than that, these holes also work as reproductive organs. Jellyfish and anemones will release their sperm, eggs, and larvae through the holes.

– Don’t have brain or heart: Corals, jellyfish, and sea anemones don’t have brains. Instead, they have a network of nerves that runs throughout their bodies. Sea anemones lack eyes and rely on chemical and tactile signals

– They are edible: You can also eat the flower of the sea, just like you eat jellyfish. Most of them are safe and edible. In southern Italy and southwestern Spain, the snakelocks anemone (Anemonia viridis) is a valued dish. Locals in Spain call it ortiguillas de mar. They often marinade the anemones in vinegar before coating them in batter and deep-frying them in olive oil.

– They can kill humans

Even though most sea anemones are safe to humans, some carry extremely powerful venom that can hurt or even kill a person. For example, the hell’s fire anemone (Actinodendron arboreum) can create unpleasant skin ulcers. While some carpet anemones (Stichodactyla) is poisonous enough to cause allergic reaction and organ failure, which can be fatal. If you touch a small sea anemone, you may feel the sticky sensation created by the anemone’s tentacles. This is because it tries to eat your finger.

– Most of their bodies are made up of water.

10. They are not that small

Sea anemones have many different shapes and sizes. The story anemone (Gonactinia prolifera), is one of the tiniest species of sea anemone, and they barely grow more than 5 millimeters long.

However, some species like the crusty red anemone (Urticina columbiana) and Mertens’ carpet sea anemone (Stichodactyla mertensii), can grow more than 3 feet (1 meter) in diameter. The plumose anemone (Metridium farcimen) can even reach heights of over 3 feet.

The Mertens’ carpet anemone

11. They can regenerative body

One of the most amazing sea anemone facts is that they regenerate themselves. If the sea anemone is cut into multiple parts, each component can regenerate into a new anemone. The researchers discovered that the anemone’s genes interact with one another, which explains the anemone’s ability to regenerate.

This remarkable regenerating ability could help scientists understand how to modify human gene communication, advancing the potential to treat heart problems and boost regenerative regeneration.

12. Keep as pet in an aquarium

Many aquarium hobbyists keep sea anemones as marine pets. give a pleasing diversity of colors and textures to aquariums. However, it’s very hard to keep them alive because most species are really sensitive to changes of water (temperature, pH, and oxygen levels).

The popularity of sea anemones in the pet trade can be harmful to their populations. The majority of sea anemones are caught in the wild, which might lead to overexploitation in some regions.

13. Play an important role in the ecosystem

These beautiful creatures play a crucial part in the ecosystem. Sea anemones are essential predators in their natural habitats, and they also provide homes for a variety of fish, algae, and crustaceans.

They are also prey for some sea stars, snails, crabs, and fish. They increase the diversity of species in coastal ecosystems and other habitats. However, sea anemones face many dangers, including over-exploitation, water pollution, and climate crisis.

14. There are 1000 anemone species

Actiniaria is sea anemones scientific name. They are separated into 46 families and there are about 1000 different species of this marine anemone. Here are some of them:

Beaded Sea Anemone has a bead-like structure down to the length of its tentacles, which can make you feel sticky when touching. They usually have subdued colors, like green, purple, and brown, on the highest part of the tentacles. While the hue of orange or red is normally seen on the bases. If threatened, the beaded anemone can attach itself to a buried object and pull its tentacles fully beneath the seafloor.

Adhesive Sea Anemone contains two types of tentacles: five (or more) tentacles within the mouth are small and short tentacles, while the remainder of the body’s tentacles are long. These tentacles will have different colors, usually in pairs of brown/green, pink/yellow, or grey/blue.

Magnificent Sea Anemone is the world’s most photographed anemone thanks to its beauty and impressive size. The color of its tentacles and its column-like body are totally contrasted. While the blunt-end tentacles are muted green and brown, the body is way much brighter with the color of white, red, purple, green, and blue.
This type of anemone likes an exposed environment. That’s the reason why it frequently attaches itself to a robust piece of coral or rock and creates a big group.

Bubble-Tip Sea Anemone lives in the same seas as the adhesive anemone and in East Africa. These anemones have symbiotic relationships with several types of fish (such as clownfish). They prefer to attach deep into holes or cracks, leaving only the tentacles showing while hunting.

Green sea anemone: the green color of this anemone mostly comes from microalgae (zoochlorellae) and dinoflagellates (zooxanthellae). They are unicellular organisms that have a symbiotic relationship with the anemone and they live in its cell. They photosynthesize and supply nutrients and green color to their host.

Giant carpet sea anemone is about 40-50cm in diameter when out of water. Its huge oral disk is covered in short tentacles, resembling a shaggy carpet. Unlike Merten’s carpet anemone, the oral disk is frequently folded and rarely retained flat on the surface. Its body can vary in different colors like orange, pink, or yellow.


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