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How are the stinging cells arranged? Function of Stinging Cells

Interesting features are characteristic of a group of multicellular animals that are of the type Strekaya, or Cnidaria. Knidarias have a simple structure, but they have real tissues, an intestinal cavity. One of the unofficial names of the group is coelenterates. Stem cells (cnidocytes, nematocytes) play an important role in the body. They serve to attack prey and defenses from enemies.

Which organisms possess cnidocytes?

Stalking - sea and freshwater animals that live in almost all latitudes. The radially symmetrical body of the cnidarians has one of two types of constitution - polypoid or medusoid. Representatives of the first type differ significantly in appearance, some more like plants. In the jellyfish, the mouth and tentacles are directed downward. As a rule, these coelenterates float freely, and two forms of the body alternate in different generations. Stem cells exist in almost all cnidarians, they are located on tentacles. Freshwater coelenterates are smaller than marine. Among them are solitary and colonial organisms.

The Shrining type combines the following classes of animals:

  • Hydroid (Hydrozoa);
  • Scyphoid (Scyphozoa);
  • Coral polyps (Anthozoa);
  • Cubomeduza (Cubozoa);
  • Polypodia (Polypodiozoa).

How are the stinging cells arranged?

Translated from the Greek language, the word "cnidos" means "nettle," which is due to the presence in the outer cover of animals capsules filled with a poisonous secret. As a rule, stinging cells are concentrated in the tentacles of the cnidarians and are provided with a sensitive cilium. Inside the cnidocite is a small sac and a folded miniature tube - a stinging thread. It looks like a compressed spring with a harpoon. An important role in the activation of burning cells belongs to calcium ions, a change in the concentration and pressure of the solution inside the capsule. It should be noted that Cnidarians do not react to all external stimuli, so as not to waste stinking cells. On the animal's body, there are nerve endings, or receptors, that help detect changes in the environment.

What is the function of stinging cells?

A small contact with the prey or enemy, changing the water pressure from the moving object can lead to stimulation of the sensitive hair. Knidocytes are also able to react to proteinaceous substances. This is what happens when exposed to a stinging cell:

  1. The lid opens on top, facing the environment.
  2. The crotch thread straightens and, together with sharp spikes at the base, pierces the victim's body.
  3. The cnidocite wraps around or sticks to the prey.
  4. The released poison causes paralysis or a burn.
  5. After completing their function, the cnidocytes die, and in 48 hours later new ones develop.

Due to the high concentration and coordinated activity of the cnidocytes on the tentacles, coelenterate animals affect the predator or potential prey. Neurotoxins inside the capsules of stinging cells paralyze a small prey and cause burns in large organisms.

Who does the hunted animals shoot?

In the course of the experiments it was established that the cnidocite emits a "harpoon" and poison within 3 milliseconds after contact with another animal. The lightning-fast cellular reaction has practically no analogues in living nature. Its speed and strength, with which the stripping filament is released, is sufficient to penetrate into the hard shells of some crustaceans! Large representatives of coelenterates attack fish and hermit crabs. But for most cnidarii, small organisms such as plankton and benthos serve as a food source. It should be noted that many coelenterates can not be rescued from predators even by stinging cells. Possessing such a formidable weapon in the tentacles, they nevertheless become the object of hunting for other animals.

How do the flowers of the animal world feed?

Coral polyps form colonies in the seas and oceans. Actinia or sea anemones live alone, attaching to the soles of stones, shells, rocks and reefs. Tentacles and mouth polyps that belong to the Anthozoa class are usually located at the top, the lower part is attached to the substrate. The mouth of the sea anemone is surrounded by tentacles, on which there are cnidocytes. The function of stinging cells of marine anemone lies in attacking prey and defending from enemies. The actinia are capable of paralyzing and entangling with burning threads of small animals. Some cnidarians pull out the tentacles, which is necessary with a fixed lifestyle.

The very fast action of neurotoxins of stinging cells also solves the problem of food production. Upon contact, they can immobilize the prey and repulse the attack of predators.

Where do hydroids live?

Representatives of the Hydrozoa class are found in fresh water bodies, Antarctic waters, deep ocean basins. Relate to this group are hydras, limnomeduzy, siphonophores, other subclasses and detachments. Most of them are predators that hunt with the help of cnidocytes. Streptococcal celiacs belonging to the hydroids have significant differences in the size and strength of the venom. There is a division of functions between groups of organisms in colonies of polyps: some feed, others protect, others serve for reproduction. Some jellyfish get their food, drifting in the water with fixed tentacles, into which plankton gets into, while others actively swim in search of food. There are coelenterates, which are able to purposefully hunt for the victim, whose approach is signaled by receptors on the surface of the body.

Are cytofacilli and cubomedusis dangerous?

The sizes of animals belonging to the class Scyphozoa range from 12 mm to 2.4 m in diameter. Even in large forms there is no skeleton, head, respiratory organs. A typical representative of this group is a semi-transparent aurelie eared - less toxic than other jellyfish. Adult individuals feed on plankton that adheres to the tentacles. Scyphomedusae have a variety of cnidocytes and receptors surrounding the mouth and tentacles. Their main purpose is to recognize and paralyze prey.

Deadly for small animals are the stinging cells of a giant cyanide (Cyanea arctica). And when it comes into contact with a person, the cnidocytes cause a burn of varying severity. More often there is a rash and redness from exposure to toxins that get on the skin. Kubomeduzy - the inhabitants of the warm waters of the seas and oceans - are able to move quickly. Some of them are dangerous to humans: burns resulting from such "communication" can lead to death.

The intestinal and human

The problems of human relationships with animals, which are of the type Strekaya, are very diverse. Many divers and fans of beach holidays on the ocean are familiar with the stinging properties of coelenterates. Stinging cells are characteristic of jellyfish floating in the water column. Even easy contact with many of them can lead to painful conditions, burns, skin irritation. To enjoy diving or swimming, you just have to follow the rule, which reads: "Watch, but not touch." The best remedy for burns with tentacles of jellyfish is hot water, then a cold compress and taking antihistamine medications. One of the complex problems of interaction between the population and coelenterates is the extraction of corals for the manufacture of jewelry, souvenirs. In recent years, the dismay of scientists is the death of polyps - builders of rich and complex underwater structures. They create an environment not only for themselves, but also for other invertebrates, as well as fish. Coral reefs in warm oceans and seas around the world are experiencing a significant impact of climate change, salinity and other water properties.

Polyps colonies grow very slowly, only a few millimeters a year increase. Without coral buildings it is difficult to imagine the underwater world, which so attracts with its unique beauty and special charm.

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