Earthworms are good at splitting in two? My sea anemone can split in a hundred

As summer comes to an end, the best time of the year to go fishing is almost here (the temperature in summer is more suitable for fishing), so if you haven’t gone fishing yet, hurry up!

Recently, everyone's trophies from fishing are very rich. In addition to the common clams, swimming crabs, conchs, razor clams... there are also some mysterious creatures that we dare not recognize, such as this:

From TikTok: Daqi Going to the Sea

This thing that looks like a chrysanthemum and a jellyfish is actually an anemone. Depending on the species, its shape can be very strange.

From TikTok: Daqing Seafood Hunting

Sea anemones are not edible, but some species are used to make soup.

Digging sea anemones to make soup, from Douyin: Hey cousin

Having said that, most anemones are toxic and are not recommended for eating. As for whether they taste good or not, Tadpole Jun doesn’t know… (If anyone has tried it, please tell us in the comments section)

Although sea anemones are often "caught" by humans, they are creatures with very strong survival abilities in the sea!

Many sea anemones have a secret weapon – they can replicate themselves by “splitting in two” like earthworms, and they even use this skill as a way to expand their sphere of influence.

Just like this, the "cluster anemone" in "Octonauts"

Moreover, many anemones look too much like plants, and many people cannot tell the difference between animals and plants.

Is the sea anemone a plant?

Although their name sounds a bit like a plant and they look a bit like blooming flowers, sea anemones are actually animals and are closely related to corals, which are often mistaken for plants.

Sea anemone, image from Wikipedia

Sea anemones belong to the class Anthozoa, phylum Coelenterata, and are a type of multicellular organism that is relatively primitive in evolutionary history.

It is generally believed that the phylum Cnidaria has three classes, namely Hydrozoa, Scyphozoa and Anthozoa, among which the animals of the Anthozoa are the backbone of the "underwater garden".

Colorful corals, photo courtesy of hippopx

Most of the sea anemones we talk about come from the order Actiniaria in the class Anthozoa. If we call all animals in the class Anthozoa "corals", then it is reasonable to say that sea anemones are corals.

Whether it is anemones or other members of the class Anthozoa, they only live in the ocean. Their common characteristics include radial symmetry (that is, there are multiple sections through the central axis of the animal's body that can divide it into two equal parts), two germ layers, a primitive digestive cavity and a nervous system, etc.

In addition, the phylum Cnidaria is also called the phylum Cnidaria. The so-called "cnidaria" means that these animals all have stinging cells, such as corals and sea anemones. They can use the stinging cells on their tentacles to prey.

Various types of anemones, image source: The royal natural history

So how do we distinguish between anemones and the corals we usually think of?

Generally speaking, sea anemones are individuals, while corals are groups; also, sea anemones have no skeleton, while the coral polyps that form corals mostly have skeletons.

To replicate in order to fight

Sea anemones can reproduce sexually . The sperm and eggs they produce are fertilized in seawater or in the female's body. The fertilized eggs develop into planula larvae, which can move freely until they find a suitable environment to settle down, settle down and undergo metamorphosis to become independent sea anemone individuals (some species of fertilized eggs develop into sea anemones before leaving the mother body). After that, the sea anemone no longer moves or only moves in a very limited space.

Of course, sea anemones can also reproduce asexually , usually by longitudinal fission or budding, in which they split in two.

Perhaps because they always live in the same place and look like plants, many people imagine sea anemones as creatures with no fighting power. In fact, sea anemones are carnivores . They not only eat plankton in the ocean, they can even prey on fish, crabs and shellfish. Sometimes they even eat thick-skinned starfish. Their fighting power is quite fierce.

Sea anemone eating shrimp. Image source: Small Science

Sea anemones are so fierce that they inevitably fight with each other for territory, but adult sea anemones can hardly move, so how can they expand their territory? They choose a special fighting strategy - self-replication , and the powerful asexual reproduction ability supports them in doing so.

Anemones of the same species fighting each other. Image source: Animal World

Many sea anemones clone themselves in large numbers to form large colonies in a short period of time in order to firmly control their territory. The yellow sea anemone (Anthopleura xanthograrnmica) is one of the best examples. They can of course reproduce sexually, but when fighting for territory, they have to rely on asexual reproduction (fission) to ensure efficiency.

When two different families of yellow anemones (with different DNA) meet each other (for example, they set their eyes on the same reef), they often fight fiercely, scrambling to replicate more individuals in order to gain an advantage.

Sometimes, the anemones on the front line of the conflict will even use the stinging cells on their tentacles to attack each other, just like the "cluster anemones" in the cartoons.

Unique sea anemones

The ability of "self-replication" alone is not enough to make them stand out. Many anemones are also quite distinctive in terms of "appearance" and win attention with their unique shapes, such as the cute pacifier anemone.

The pacifier anemone is also called the Entacmaea quadricolor. Its appearance is very eye-catching, and its tentacles are like pacifiers for children to drink milk, which is quite cute.

The shape and color of the pacifier anemone vary greatly, including purple, orange, red and green. It is a common anemone in marine aquariums.

Nipple anemone, image source: Global Biodiversity Information Facility

Unlike the cute and silly style of the pacifier anemone, the princess anemone is bright and beautiful, with great visual impact.

The Princess Anemone (Heteractis magnifica) is quite large, with one end of its cylindrical body attached to the rock and the other end having a crack-shaped mouth. The oral disc of some individuals can be up to 1 meter long.

This anemone is mainly distributed in the Indian Ocean. It has a variety of colors and is dazzling. Blue, green, red, purple and even brown can be seen. Many kinds of clownfish often live in it.

The gorgeous Princess Anemone, photo courtesy of iNaturalist

Compared with the pacifier anemone and the princess anemone, the carpet anemone is much more low-key. Although it is known as the largest anemone, it actually does not look ostentatious.

The carpet anemone (Stichodactvla mertensii) can reach a diameter of more than 1 meter. It mainly lives attached to rocks. Its mouth is covered with short tentacles and clownfish live around it.

Although it looks low-key, its lethality is "high-profile". The stinging cells on the tentacles of the carpet anemone are their weapons. The stinging cells not only harm the surrounding corals and other anemones, but can also sting human skin, causing allergic itching symptoms. It is one of the few anemones that can cause great harm to humans.

Carpet anemone and surrounding fish. Image source: iNaturalist

For most people, sea anemones are quite unfamiliar animals, but they are an important link in the marine ecological chain, and they have very unique personalities!

Which type of anemone do you think is the most beautiful and interesting?

END

Review expert: Li Weiyang, well-known science blogger

Tadpole Musical Notation original article, please indicate the source when reprinting

Editor/Xiao Xitushuo