Marine Invertebrates

Sea anemone

  • Scientific name:  Actiniaria
  • Common name:  Sea anemones or Actinias
  • Aquarium size: 400 to 500 liters
  • Temperament: Pacific
  • Temperature: 23ºC to 27ºC
  • pH: 8 to 8.3
  • Diet: Carnivores
  • Length:  2.5 cms. to 10 cms. some specimens can measure up to 1.8 meters in tropical seas

What is an anemone?

Actinias, also known as marine anemone, are invertebrates belonging to the order of hexacoral anthozoans that are usually differentiated by being sea ​​animals capable of adhering to the substrate (in the case of reef anemones), to rocks, sand and even to the shell of mollusks and crustaceans.

Quite similar to a showy plant, many people are unaware that it is really an animal . However, of these solitary polyps there are at least 1,200 described species in the world. The extraction of these species from their habitat as a characteristic decorative element of large marine aquariums has more and more followers, becoming one of the most popular exotic marine animals among ocean lovers.

Description and characteristics of anemones

With a vegetal appearance and colors that range between pink, red and orange, actin has multiple tentacles that move, resembling the swaying of marine flora, which is why it is often confused with a plant, however, this slight mobility has to do with checking and analyzing the space, and it is precisely for this reason that it can identify possible prey through movement and temperature changes in the water.

This analysis is possible thanks to a complex network of sensors that allow them to perceive the world around them and hunt their food, even though they do not have specialized sensory organs such as eyes, ears or tongue.Your nervous system, although primitive, is responsible for coordinating all the processes involved in homeostasis, which includes physical and biochemical responses to any stimulus. They have elongated cylindrical bodies that can be smooth on their outer wall or have some protrusions, also provided with a gelatinous layer called mesoglea that serves to develop an amazing plasticity and flexibility; feature used to contract or stretch, resist strong ocean currents, and of course, stay fixed in place in the water.
Although the sea anemone is related to jellyfish and corals, it  is itself a sea animal. Some research done by Genome Research magazine

suggests that according to its genetic code, the anemone is in fact half plant, due to the similarity found in its regulation of gene expression known as micro RNA.

This incredible animal also lives in mutualism with various species such as the clownfish , undoubtedly its most famous relationship. The clownfish is naturally covered by a mucosa that gives it immunity against the sting of the anemone, so that it can hide between its tentacles to flee from predators, and in return, the anemone takes advantage of the food remains that the anemone can provide. clownfish.

Varieties of sea anemones

Some of the most popular varieties of sea anemones are:

Distribution and habitat

The sea anemone can come to have different forms that differ in their appearance and in the place they inhabit. Thus, we can find a type of small anemone that can measure between 2 and 5 cm, whose preferred habitat is rock walls with sufficient lighting that are 5 meters from the surface, as well as another type of anemone, which, Although it also adheres to illuminated rock formations, it can be found in waters up to 25 meters deep and can reach 50 cm or more.

Actin is found in all oceans with diverse distribution, however, the largest number of species have been observed in the Great Barrier Reef in Australia and in the waters of the Mediterranean Sea.

Anemones in the aquarium

Although they are very attractive, anemones are definitely not recommended marine animals for those who are starting to build their own aquarium, because they require certain special care.

Its large size is the reason why your aquarium should have at least 400 liters of capacity, in addition, to include an actin, it is recommended that the aquarium has been in use for a year and that it has very good lighting.

The water temperature must be kept between 26-27 ºC with a Ph 8.3 (max) and a density of 1.020.

Anemone sting

Most sea anemones are harmless, however, there are cases of people who have been bitten by a sea anemone. The amount of toxin that they are capable of injecting is not considered dangerous for humans, except in cases of proven allergy, a sting that can also be treated with conventional first aid and a little hot water in the affected area.

What do sea anemones eat?

Fish are an important part of the diet of actinias , but they can also eat other unsuspecting creatures such as zooplankton, worms, larvae, and crustaceans. Their large polyps allow them to ingest large prey, even larger than themselves, which they immobilize by injecting venom when they approach.

They can eat at any time whenever they have the opportunity, but if they cannot find food, they could die as they cannot move.


While some species of actin are hermaphroditic , others have separate sexes giving way to asexual or sexual reproduction. Through an intricate process known as lateral fusion, the sea anemone can carry out its asexual reproduction, where internally, an exact portion of itself will incubate which will be expelled to the outside through a lateral opening.

In contrast, in sexual reproduction, the sperm and eggs will be dispersed in the water in which fertilization will occur once they bump into each other. Of these stages, only a small number of anemone zygotes will survive to reach maturity, clinging to rock formations with enough light to survive, and those that do may live for about 50 years or more.

Photographs of sea anemones


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