The strikers include hydra, jellyfish and sea anemones. Corals and sea anemones inhabit predominantly warm seas.
The smallest are some hydra, whose size is about 1 mm, the largest one can be called the cyan hairy jellyfish, the length of its tentacles can reach 40 meters, and the diameter of the body exceeds 2 meters.
Body structure
The body of any bowing contains a single large cavity, at one end of which there is a mouth opening surrounded by tentacles. The body cavity is surrounded by a wall consisting of 2 layers of cells, and a gelatinous substance between them. The inner cell layer forms the tissue involved in the digestion of food. In the outer layer of cells are muscle fibers, so organisms can respond by movement to external stimuli. From the nerve cells a network forms, the simplest nervous system. In the outer layer of the body and tentacles, special striking cells are located. The animal injects poison into the body of the victim or enemy as part of such a cage that resembles a harpoon. All barking carnivores and feed, attracting the victim to the mouth with tentacles.
Forms of existence
Animals have 2 forms of existence: polyps and jellyfish. The body shape of the polyp (hydra, sea anemone, and coral) resembles a vase. The polyp's mouth opens upward, and at the other end it attaches to the bottom of the reservoir or to other surfaces. And the body of a jellyfish resembles an umbrella or an inverted bowl.The jellyfish's mouth opens down and it drifts freely in the water. Some stingrays, for example, eared aurelia, are jellyfish at the stage of the adult organism, and polyps at the stage of larva. This species of aquatic animal leads a different lifestyle.
Lifestyle
Sea anemones are motionless animals, they live at the bottom of a reservoir, having fixed in one place. They live apart and, thanks to their brightly colored tentacles, resemble, rather, a plant than an animal. The wide, domed body of jellyfish is well suited for swimming in water. Jellyfish move, swinging on the waves or using the flow, alternately reducing and relaxing their body: the water pushed out from under the domed body pushes the animal forward. Some of them are extremely toxic and their touch can be fatal even for humans. Hydroids are fixed on plants, stones, etc. The place is changed extremely slowly: on the surface they are alternately fixed first with the sole and then with tentacles, i.e. move as if tumbling.
Coral
Like some of the animals listed above, corals also live, entrenched in one place. Most of their species forms a solid calcareous skeleton around the lower part of the polyp. Corals live in large colonies in which calcareous skeletons come together. And they, in turn, fix new corals, thanks to which the colonies can reach impressive sizes. Despite the fact that colonies grow only a couple of centimeters a year, over several thousand years they can form coral islands of various shapes.
When water is polluted or at too high a temperature, algae living in symbiosis with corals die, which leads to the death of corals, as a result of which only colorful, lifeless white skeleton remains from colorful colonies.
