Approximately two-thirds of the species on Earth are arthropods. They live in fresh and s alt water bodies, underground and on its surface, and many of them are able to move through the air. What are the characteristics of arthropods? You will find examples of animals, their description and structural features in this article.
Who are arthropods?
Arthropods are one of the most numerous and diverse groups in the animal kingdom. It includes about two million species. Their number is increasing every year due to the discovery of new species.
The list of arthropods includes crustaceans, arachnids, insects and centipedes. They inhabit all climatic zones of the planet, from the hot tropics, up to the regions of the Arctic and Antarctic. Representatives of this group live in deserts, forests, swamps, ponds and other ecosystems. Some of them feel comfortable in human homes.
Since arthropods live in almost all environments and regionsof our planet, their appearance and adaptation to environmental conditions are very different. Their sizes range from a millimeter to several meters. The way of eating also varies greatly. Some species are exclusively predatory, others, on the contrary, are herbivorous. They can also be parasites, necrophages (scavengers), or filtrates.
What do arthropods have in common?
They are so different that the question involuntarily arises: why were they assigned to one group? In fact, arthropods also have common features. Their body and limbs are segmented and divided into sections (tagmas), or segments. That's where the name comes from.
In many species, the head and several departments merge into one, forming a cephalothorax. Limbs extend from the underside of the abdomen or cephalothorax. They breathe with lungs, tracheae or gills. The circulatory system is open and enters the body cavity. They reproduce by laying eggs or eggs. Larvae tend to be different from adults.
Arthropods are animals with bilateral symmetry. Outwardly, the right and left halves of their bodies look the same. All of them have an external skeleton. It is a thin but strong cuticle made of chitin. It does not stretch, so as it grows, the animal sheds it to grow a new one. This process is called molting.
Centipedes
Perhaps one of the most unpleasant groups of arthropods for humans is centipedes. These include various types of skolopendra, common flycatchers, drupes, nods, etc. They are mostly small (up to 10 cm), but some species grow up to 35centimeters long.
Their name is fully justified, because centipedes have up to two hundred pairs of limbs. They prefer damp places and live in forests under tree bark, under moss, rocks and fallen branches, but can live in dry and arid areas. The bathrooms of the apartments also attract them.
During the day, animals hide in secluded corners, and at night they come out to hunt. Centipedes are predators. They feed on flies, cockroaches, spiders, fleas and other small animals. Sensing danger, they curl up into a ring, and glands on their backs secrete poisonous or repellent substances for opponents: iodine, quinone and hydrocyanic acid. For humans and pets, their poison is not dangerous, if there is no allergy, then only a slight reddening will remain from the bite.
Arachnids
The class Arachnids covers not only spiders, but also ticks, salpugs, scorpions, flagellates, false scorpions, etc. Most of its representatives live on land, although some species of spiders and ticks live in water bodies. They are distributed in all regions of the planet, except for Antarctica. Scorpions inhabit mainly areas with a warm or hot climate. Some spiders and mites even live in polar and circumpolar regions.
In size, arachnids range from hundreds of microns (some mites) to 20-30 centimeters (scorpions, s altpugs, tarantulas). Their body is divided into cephalothorax and abdomen. They are characterized by the presence of leg tentacles (pedipal), oral jaws (chelicerae) andfour pairs of legs.
In scorpions, the second part of the body is elongated and resembles a tail. At the end of the "tail" is a small segment with a needle. It releases toxic substances. Their pedipals are enlarged and play the role of pincers for capturing prey.
Only jumping spiders and certain types of mites feed on plants. The rest of the arachnids are predators. They eat insects and small animals. Some hunt prey by stalking it, others build web-like traps.
They paralyze their prey with their bite, so almost all of them are venomous. Not all poisons are strong enough to infect a person. Bites of black widows, argiope, tarantulas, six-eyed sand spiders are considered dangerous.
Insects
Insects are the most numerous class of arthropods with bilateral body symmetry. More than one million species have been discovered. These are all kinds of bugs and butterflies, flies, ants, termites, cockroaches, moths, grasshoppers, etc.
The main feature of many insects compared to other arthropods is the ability to fly. Dragonflies and some flies reach speeds of up to 15 meters per second. Those insects that do not have wings run or jump (fleas, grasshoppers).
They live in completely different environments, even in water. Some live there all their lives (divers, whirlwinds, water striders), others only a certain period in development (dragonflies, caddisflies, hydrophiles). Their limbs are modified so that they allow animals to glide freely on the surface.water.
Insects live alone or in groups. They feed on both plant and animal food, dead organisms and the remains of animal life. In search of food, they are able to overcome hundreds of kilometers a day (locust).
Public insects can be combined into large groups, within which there is a clear hierarchy and division of responsibilities. So, for example, ants, bees, termites, bumblebees live.
Crustaceans
The group of crustaceans covers more than 70 thousand species, including crayfish, crabs, shrimps, lobsters and other animals. Most of them inhabit fresh and s alt water bodies. Woodlice and some crabs prefer wet areas.
All crustaceans have two pairs of antennae (antennae and antennules), and their limbs are bifurcated at the ends. They breathe mainly with gills. In some representatives, gas exchange occurs throughout the surface of the body. Sea ducks and sea acorns are immobile, attaching themselves to rocks, stones and other surfaces.
By the nature of nutrition, many crustaceans are filtrates. They eat small organisms such as plankton, detritus. In addition, they eat dead animals, cleaning water bodies. The crustaceans themselves are food for fish and aquatic mammals.
Man also eats them. In countries located by the sea, crustaceans occupy a large share of the fishery. And the sea duck is considered one of the most expensive delicacies in the world.
