Features of the structure and vital activity of crustaceans. The value of crustaceans in nature and human life

The branch of biology, engaged in the study of animal organisms inhabiting the globe, is called zoology. One of its sections directly examines a group of multicellular animals - crustaceans. Their structure, features of vital activity, as well as the significance of crustaceans in nature and human life will be considered in this article.

Systematics of crustaceans

Among the invertebrate organisms inhabiting our planet, animals are isolated that combine into Type Arthropods. Crustaceans are one of the supraclasses of this taxon, whose representatives live mainly in fresh or sea water. Only some of them, for example, lice and land crabs, live on wet land sites. In the Superclass Crustaceans enter: a class of inferior crayfish and a class of higher (decapod) crayfish.

In turn, each of these taxa consists of smaller systematic groups - groups. Lower crustaceans serve as the basis of zooplankton, therefore they are of great importance in nature and human life. Essentially, being one of the first links in food supply chains, lower cancers are the fodder base for fish and aquatic mammals. Thanks to the representatives of the orders of the isopods, copepods and branched-bodied, marine inhabitants receive a high-grade protein feed, since the composition of the body of lower cancers includes easily digested polypeptides.

The class of higher crustaceans includes one detachment - decapod crustaceans, which is represented by animals such as crabs, lobsters, lobsters and shrimps.

Features of the structure of crustaceans

The division of animals into classes is based primarily on differences in the external structure of these organisms. In lower cancers, such as the Cyclops (order of copepods), daphnia (a branch of the branchy), the mocrica (order of the equinoxes), the body contains a variable number of segments (segments), and the abdomen lacks limbs. On its last segment there is a specific education - a fork. The body itself has a soft and thin chitinous membrane through which the internal organs of the animals show through.

Higher crustaceans, whose representatives have hard chitinous shell impregnated with lime, are also characterized by a strict division of the body into the cephalothorax and abdomen with a constant number of segments in them. Thus, river crayfish have 5 and 8 segments in the cephalothorax, respectively, and the abdomen has 6 segments. Also, the higher crayfish, unlike the lower crayfish, have swimming legs on the abdomen.

Metabolism and vital functions

As it was already said before, the life of crustaceans proceeds mainly in water. Therefore, they clearly manifest the so-called idioadaptations - adaptations to a specific habitat: breathing the entire surface of the body or gills, a streamlined body shape, a shell consisting of chitin and impregnated with a water-repellent substance - calcium carbonate.

Crustacean systems, such as the circulatory, respiratory and excretory, provide homeostasis - maintaining a normal level of metabolism. It should be noted that all crustaceans have an unclosed circulatory system, and the heart has the appearance of a pentagonal saccate organ with 3 pairs of valves. From it to the cephalothorax and abdomen, the arteries, through which the blood carries nutrients and oxygen to all organs of the animal, flow into the mixed body cavity, called myxocele. From it already venous blood enters the gills, where it is released from carbon dioxide and saturated with oxygen, turning into an arterial one. Through the holes in the pericardial bag, she enters directly into the heart.

Shchitni is a peculiar group of crustaceans

These animals, which are a group of freshwater inhabitants, can live in dry reservoirs. When the water evaporates, the shinen itself is buried in the soil and does not lose its viability for a certain time. Eggs deposited by the female on the bottom of the reservoir can last up to 15 years. They are easily transported by the wind along with soil particles, so the shields live almost everywhere except for Antarctica and African deserts.

The life cycle of crustaceans

Representatives of this superclass meet both its simple forms, for example, the direct development of river crayfish, as well as more complex ones, including larval stages. In this case, development is called indirect. It is characteristic for the orders of copepods and branched-bodied, and also occurs in higher cancers, for example, lobsters or lobsters. Crustaceans, whose representatives have pelagic or planktonic forms of larvae, so-called nauplii and zoae, are widespread in nature: they are inhabitants of the coastal waters of Australia, North America, and Europe. All phases of the life cycle of crustaceans are controlled by their endocrine system, represented by androgenic, post-commissural and sinus glands. They release hormones that regulate the processes of sexual maturation, molting, and the transformation of larvae into adult individuals.

The value of crustaceans in nature and human life

Animals belonging to the order of decapods, for example lobsters, lobsters, crabs, are valuable commercial species that provide human with delicacy and high-protein meat. Of great importance are representatives of inferior crayfish: cyclops, daphnia, water donkeys, which are a food for fish, for example, as valuable as salmon and sturgeon.

River crayfish, often called sanitation, cleanse the bottom of dead organic remains. Although the value of crustaceans in nature and human life is overwhelming in suppressive cases, some animals do harm, for example, carp lice cause a massive death of commercial fish species. And cyclops are intermediate hosts of parasitic worms: rishta and broad tapeworm.

We were convinced that these animals that are part of the Type Arthropod are an important link in the natural ecosystems of our planet and the value of crustaceans in nature and human life should not be underestimated. Some species of these animals (for example, broad-rooted river crayfish, mantis) are listed in the Red Book, and their destruction is punishable by law.