Interesting features are characteristic of the group of multicellular animals that belong to the type goad, or Cnidaria.Cnidarians have a simple structure, but these fabrics have, intestinal cavity.One of the informal group names - coelenterates.An important role in the body perform stinging cells (knidotsity, nematotsity).They serve to attack prey and defend against enemies.
What organisms have knidotsitami?
goad - marine and freshwater animals living in almost all latitudes.The radially symmetrical body cnidarians has one of two types of body - polypoid or Medusoid.Representatives of the first type are significantly different in appearance, some are more like plants.Medusa mouth and tentacles are directed downwards.Typically, these coelenterates float freely, and two alternate body shape in different generations.Stinging cells have almost all cnidarians, they are located on the tentacles.Freshwater Coelenterata less than sea.There are among them, solitary and colonial organisms.
type goad animals comprises the following classes:
- hydroids (Hydrozoa);
- scyphoids (Scyphozoa);
- coral polyps (Anthozoa);
- jellyfish (Cubozoa);
- polipody (Polypodiozoa).
How are stinging cells?
Translated from the Greek word «cnidos» means "nettle", which is associated with the presence of animals in the outer cover of capsules filled with a poisonous secret.As a rule, stinging cells in the tentacles focused cnidarians and provided sensitive cilia.Inside knidotsita is a small pouch and rolled a tiny tube - stinging thread.It looks like a coiled spring with a harpoon.Important role in the activation of cells belongs burning calcium ions, the concentration and pressure of the solution inside the capsule.It should be noted that cnidarians not react to any external stimuli in order not to waste stinging cells.On the body of the animal have nerves or receptors that help detect changes in the environment.
What is the function of stinging cells?
little contact with the enemy or prey, changing water pressure from a moving object can lead to stimulation of sensory hairs.Knidotsity also able to respond to the protein substances.That's what happens when exposed to stinging cells:
- opens lid on top, facing the environment.
- stinging thread straightened and with sharp spikes at the bottom is stuck in the body of the victim.
- cnidocyte twists or glued to the production.
- Allocated venom causes paralysis or burn.
- fulfill its function, knidotsity killed and replaced after 48 hours developing new ones.
Due to the high concentration and coordinated action on the tentacles knidotsitov, coelenterates animals impress potential prey or predator.Neurotoxins in capsules stinging cells to paralyze the victim and cause small burns in large organisms.
hunted goad animals?
During the experiments found that cnidocyte throws "Harpoon" and poison for 3 milliseconds after the contact with other animals.Lightning cell reaction practically has no analogue in nature.Its speed and force with which the thread is released stinging enough to penetrate the hard shell of certain crustaceans!Large representatives Coelenterata attack fish and hermit crabs.But for the majority of Cnidaria source of food are small organisms like plankton and benthos.It should be noted that many cnidarians do not save from predators even stinging cells.With such a formidable weapon in the tentacles, they also become the object of hunting other animals.
eating "flowers" of the animal world?
Coral polyps form colonies in the seas and oceans.Anemones or sea anemones live single, sole attaching to rocks, shells, rocks and reefs.The tentacles and mouth polyps that belong to the class Anthozoa, usually located at the top, the bottom part is attached to the substrate.The mouth is surrounded by tentacles of sea anemones, which are knidotsity.Function stinging cells of sea anemone is an attack on the mining and defense against enemies.Anemones are able to paralyze the burning strands entangle and small animals.Some cnidarians stretched tentacles, which is necessary for sedentary lifestyle.
problem of food production also addresses the very fast action of neurotoxins stinging cells.Upon contact, they can immobilize prey and repel the attack of predators.
inhabited hydroid animals?
representative of the class Hydrozoa found in fresh water, the waters of Antarctica, deep ocean basins.They belong to this group hydra limnomeduzy, siphonophores other subclasses and groups.Most of them - predators that hunt using knidotsitov.Cnidarian stinging cells related to hydroids have significant differences in the size and strength of poison.There is a separation of functions between groups of organisms in the colonies of polyps: one fed, the other protected, others are used for breeding.Some jellyfish get their food drifting in the water stills tentacles, which gets plankton, other actively swimming in search of food.There coelenterates that are able to specifically hunt for prey, which signals the approach of the receptors on the surface of the body.
dangerous to knidotsity stsifo- and jellyfish?
Dimensions animals belonging to the class Scyphozoa, ranging from 12 mm to 2.4 m in diameter.Even in large forms no skeleton, head, respiratory organs.A typical representative of this group - translucent Aurelia eared - less toxic than other jellyfish.Adults feed on plankton, stick to the tentacles.Stsifomeduzy have many knidotsitov and receptors surrounding the mouth and tentacles.Their main purpose - to identify and paralyze the prey.
deadly to small animals are the stinging cells of a giant cyan (Cyanea arctica).And when in contact with a person knidotsity causes burns of varying severity.Most often there is a rash and redness from exposure to toxins that enter the skin.Jellyfish - the inhabitants of the warm waters of the seas and oceans - are able to move quickly.Some of them are harmful to humans: burns resulting from such a "communication" may be fatal.
Coelenterates and people
problems of man's relationship with animals, which are a type goad, is very diverse.Many divers and fans of beach rest on the ocean familiar with stinging coelenterates properties.Stinging cells characteristic of jellyfish floating in the water column.Even slight contact with many of them can lead to disease states, burns, skin irritation.To enjoy diving or snorkeling, you need only to comply with the rule that reads: "look but do not touch."The best remedy for burns jellyfish tentacles considered hot water, then cold compress and antihistamine medication intake.One of the difficult problems of interaction of population and coelenterates is the mining of coral for making jewelry, souvenirs.In recent years, scientists anxiety causes the death of polyps - the builders of the rich and complex underwater structures.They create an environment not only for themselves but also for other invertebrates and fish.Coral reefs in the warm oceans and seas around the world are experiencing a significant impact of climate change, salinity and other properties of the water.
colony of polyps grow very slowly, increasing by only a few millimeters per year.Without coral structures it is difficult to imagine the underwater world, which is so attracted by its unique beauty and charm.
