Rodents - is it a class or a species? Are rodents a species or unit? Characteristics of rodents

The first representatives of the squad Rodents appeared in the Cretaceous era. And they became known to science from the beginning of the Paleocene. Paleontologists believe that the ancestors of rodents were insectivores.

Detachment of the Rodent: a general characteristic

Among the animals of this detachment there are representatives of completely different weight categories. The body length of the mouse is 5 cm. The capillary can reach 130 cm in length, and the mass of its body varies from 6 to 60 kg. Due to the wide variety of species, the external structure of the rodent body may differ. For example, limbs can have a different appearance. Rodents have 5- or 4-toed forelimbs and 3-, 4-, 5-toed posterior. The hair cover is very diverse - from dense and soft to pitted, bristle-shaped or even forming a needle. Coloring is also diverse. There are no sweat glands on the body, only the presence of sebaceous glands is characteristic. The location of the sweat glands is the soles. The number of nipples varies from 2 to 12 pairs.

According to the type of food, representatives of numerous families also differ. You can identify herbivorous, omnivorous, insectivorous and fish-eating rodents.

Features of the structure

Characteristic features are smooth large cerebral hemispheres; Imperfection of thermoregulation; The presence of two pairs of strongly enlarged middle incisors, which grow throughout life and do not have roots. In shape, these teeth look like chisels and are very sharp, incisors on the inside are covered with soft dentin, while the front part is covered with hard enamel. This feature of the structure allows the tool to self-sharpen if necessary. Fangs in rodents are absent, and between the incisors and molars are diastema (empty space). In total, the number of teeth in different species varies from 12 to 20.

Depending on the lifestyle and type of nutrition, the molars can be distinguished by the structure of the tooth surface. It can be tuberculate or cristate. Lips perform a protective function, protecting the mouth from various kinds of unnecessary particles. The structure of the masticatory muscles located behind the cheeks and closing the jaws allows, if necessary, to protrude the anterior jaw. It is the differences in the configuration of these muscles that served as a sign on which the rodents are classified. The stomach can be simple or multi-chambered. For all but sone, the presence of the caecum is characteristic, but there is no spiral fold in it.

Classification of the order of the rodent

The squad of the rodent is not finally classified. Until recently, the laggards, allocated today in a separate detachment, also belonged to it.

To date, more than 40 families are known, 30 of which include modern representatives of this detachment. Species diversity is very wide, in the order of the Rodent, according to various sources, there are 1600 to 2000 species.

The widespread distribution of various species of rodents allows one to speak of the numerical dominance of their representatives among mammals. 150 species from 11 modern families, including Flying Squirrels, Squirrels, Beaver, Hamster, Molehill, Mouse, Sonevy, Tushkonkovye, etc., inhabit open landscapes of temperate and subtropical belts, especially arid zones. For many species it is characteristic to maintain a semi-underground way of life, when only food is provided on the surface.

Wild and domestic rodents, leading night and day life, small and large - a great many of their representatives are settled around the world.

The value of rodents

It is known that rodents take an active part in soil formation. Their burrowing activity positively affects the productivity of plants.

The length of life depends on the size: small animals rodents live from 1.5 to 2 years, and large - from 4 to 7 years. The onset of puberty in small species occurs in 2-3 months, and in large - in 1-1,5 years. The number of rodents of the smallest size, which in a year are capable of giving birth to 6-8 times in 8-15 calves, can increase hundreds of times in some of the years. Then rodents cause enormous damage to agriculture. Among the detachment's animals there are dangerous ones, those that are carriers and agents of serious diseases. These are, for example, ground squirrels and groundhogs. Proteins, muskrats and nutria have valuable fur, and in this connection they have become an important object of fur trade. Two species and 5 subspecies of rodents are listed in the Red Book.

Typical representatives of the detachment

The families that make up the Rodion squad, listed below, include a variety of animals in their appearance and way of life.

• Sem. Squirrel: common squirrel, ground squirrel, chipmunk, Mexican meadow dog, marmot.
• Sem. Flying: flying.
• Sem. Hofer: flat gopher.
• Sem. Beaver: beaver.
• Sem. Dolonogovye: the long-legged.
• Sem. Hamsters: common hamster, Dzhungar hamster, common plague, voles, hoof lemmings, Siberian lemmings, large gerbils.
• Sem. Mole rats: ordinary mole rat.
• Sem. Mouse: mouse-baby, pasyuk.
• Sem. Snowy: garden dormouse.
• Sem. Selevinium: Selevinium.
• Sem. Mouse: a forest mouse.
• Sem. Touchetcock: fat-tailed jerboa, large jerboa.
• Sem. Porcupines: Indian porcupine.
• Sem. American porcupines: a tenacious porcupine.
• Sem. Piggy: Guinea pig, Patagonian Mara.
• Sem. Capillary: capillary.
• Sem. Chinchilla: Chinchilla, Viscah.
• Sem. Nutriium: nutria.

The evolutionary path of rodents

The fossilized remains of ancient rodents, most of them found in North America and Eurasia, were very small and outwardly resembled modern mice. Only single species were slightly more developed compared to the majority and reached the size of the beaver.

The first appeared sign, which began to distinguish rodents from other similar animals, was the structure of the jaws, or rather, the appearance of characteristic incisors. These animals were quite unpretentious and gradually adapted to different habitats, while the features of the structure, depending on the way of life, began to stand out more and more clearly.

Ancient small rodents moved by running, and then appeared such species that learned to jump. In parallel, a group of underground rodents separated, the structure of the skull, claws and claws of which became characteristic.

Some of the most common rodents - mice and rats - appeared much later. Representatives of ancient species of these animals were found in the European strata of the Pliocene.

Settlement of the representatives of the detachment is mainly connected with the person, after all the rodents were "stowaways" on ships on sea expeditions, and later traveled with camel caravans in the desert, and by trains on the railways. They live next to a person to this day. Very comfortable feel in homes and livestock farms, in grain stores and in storehouses with provisions.

Rodents: the names of genera of major pests

Rats are representatives of the genus rattus, numbering 63 species. These animals are settled around the globe. But 2 species of rats inflict particularly serious damage on humanity, damaging crops, destroying food products and carrying disease. This is a black and gray rat, often called a pasyuk. Both are bright representatives of human spongers. From the point of view of a way of life it is possible to reveal some differences between representatives of these species. Black is a more "whimsical" rat. The rodent loves warmth and dwells, as a rule, in human habitation, while the pasyuk quite comfortably feels outside the home, furrowing the expanses of villages and villages. The black rat got its ubiquitous distribution when traveling on ships. In Britain, it was these rodents that became carriers of the plague that claimed millions of human lives. The native land of the Pasyuk is China, from which in the first half of the XVIII century. The rodent got to Europe, pushing away the black rat. Both kinds of rodents are very dangerous. They can be carriers of plague, typhus, leptospirosis, toxoplasmosis.

Mice are relatively small rodents. Species with this name are found in several families. The most typical representatives of the temperate climatic zone are the mouse and the mouse; African continent - herbal mouse and striped field mouse; Australia - Asian wood-fiber and prickly rice hamster. But the most famous after all is the house mouse, despite its small size, which poses a serious threat to human health. Other mice affect the economic situation of countries, damaging crops of agricultural plants and stocks of food products. This problem is particularly acute in the tropics. Almost all mice are omnivorous, but preference is given to plant foods and only occasionally they use insects. Mice are considered one of the smallest mammals. A striking example is a dwarf hamster, whose weight is no more than 10 g.

Vole are close relatives of hamsters, rats and mice. Voles and lemmings are part of the characteristic subfamily, whose representatives inhabit the cold regions of the Northern Hemisphere. In the outer structure there are characteristic features: a short tail and a rounded nose. The largest animal of 99 species of this genus is the American musk rat, also called muskrat. These mammalian rodents adapted to life in the water, having acquired in the evolutionary process special morphological features. Being mostly herbivorous, the voles become a threat to the agriculture and food industry. These rodents are fed by many mammals and birds of prey, which indicates their ecological significance.

Interesting facts about rodents

• Rodents are so widely spread on the planet that all continents are flooded with the exception of Antarctica.
• The largest rodent inhabited the territory of South America 4 million years ago. The weight of individuals could reach 1 ton. To date, the largest representative of the detachment is capybara.
• One Malayan porcupine was in the Guinness Book of Records, having lived 27 years and 4 months.
• Japanese scientists-genetics have deduced a kind of the rodent-mutant. A distinctive feature of the laboratory mutant is that it is able to tweet as a sparrow.
• The image of the chipmunk is on the arms of the two cities of the Sverdlovsk region - Volchansk and Krasnoturinsk.
• In the Chinese calendar there is a year of the Mouse, and in the Zoroastrian - the year of the Beaver and the year of the Squirrel.
• The most popular rodents is the team of cartoon rescuers from the work of Walt Disney: chipmunata Chip and Dale, rat Rocky and mouse Gaik. Also widely known rodents with funny voices from the comedy film "Alvin and the Chipmunks".
• Professor Jenny Morton of Cambridge University conducted research on the effects of methamphetamine on mammals. Experiments were conducted on the mice. It was casually found out that loud music strengthened toxic properties of a preparation. Of the group of 40 individuals who listened to Bach, only 4 died during or immediately after the experiment. But of the 40 mice who listened to the music of The Prodigy, 7 immediately died on the spot. The point, of course, is not at all that individuals aesthetically distinguish what they have heard, but in the action of rhythmic pulsating noise, which provoked an increase in the toxic effect.
• Smart rats are alcoholics. This feature really distinguishes this species. Rodents, which more successfully overcome the maze, can not resist the "glass". Such an unusual conclusion was made by professors of the University of Concordia of Montreal. Those individuals who were well oriented in the labyrinth, quickly realized the relationship of alcohol and the feeling of euphoria that it causes. This is indicated by the fact that they, having smelled the smell of alcohol, began to lap him. But less intelligent rats did not catch this connection and did not even approach the glass, frightened by the unpleasant smell of alcohol.
• Using a virus that originates from HIV, scientists from the California Institute of Technology conducted amusing experiments, transmitting to animals some genes that possess certain properties from other creatures. In particular, an impressive experiment was conducted: a jellyfish gene was introduced into the unicellular mouse embryo, which determines its glow. Surprisingly, the mice with the alien genome were born with luminous green fluorescent light organs. The glow turned into a stable property of these mice, and further offspring also had this feature.

Home Rodents

Kids often dream of a pet. But only a few have the patience, energy and time to care. The most unpretentious in this regard can be called domestic rodents. Care for these funny little animals is minimal. The content does not require special conditions, and the cost is quite affordable.

As the first pet for a small child you need to choose just rodents. After all, the kid can feed himself a funny little animal, and take part in cleaning the cage.

Pet stores offer a great variety of pets such as rodents. The list of the most common is given below.

A huge number of hamsters, rats, mice, guinea pigs, gerbils, chinchillas, ornamental rabbits, chipmunks, ferrets and even squirrels are sold in stores. The most "comfortable" are, of course, hamsters, which differ calm and complaisant character. In addition, they are very easy to tame. Squirrels, chinchillas, rabbits and ferrets need more space, and care for them is more complex.

Given that rodents are carriers of many diseases, it is necessary to periodically conduct hygienic procedures aimed at their prevention. For example, newly acquired animals must remain in quarantine for a while, which is necessary in order to make sure that they are healthy. It is also important to periodically disinfect the equipment and disinsect the skin parasites.

Rats in New York

Despite the fact that mammals are the most evolutionarily developed class, rodents (like rats) are a by-product of civilization. They developed together with us, and the more human settlement - the more beautiful the rodents feel among people. Probably, that's why New York was chosen for the world capital of rats.

According to approximate information, in this city the number of rats is eight times higher than the number of people. Whatever methods of fighting rodents invented by the city authorities, these mammalian rodents still found a way to survive.

Unwanted neighbors become more and more large, strong and prolific over the years. Also interesting is that city rats are much more cunning than rural ones. They have learned to understand many things. For example, if one of the individuals died, after swallowing the bait, its relatives would never eat it. They studied underground communications and are able to move around the city on certain routes.

Rats live next door to a man for many centuries, multiplying with lightning speed. A rat at the age of 8 weeks is still asexual. A year later, it is capable of producing 50 offspring each year. They, like artists of the circus, can be pushed through a narrow hole, perfectly climb the vertical surface and swim. They have an excellent sense of smell and touch, are capable of jumping several meters in length and are resettled by social formations.

Recently it was found that many cats stopped attacking rats. Now they peacefully coexist with them, eating together and coexisting side by side. The reason for this is the equation of forces, which in the course of evolution in rats significantly multiplied.

Even the New Yorkers themselves stopped paying attention to the rats, they now complement the urban look. The rodents stopped hiding, they stroll about the edges of the sidewalks, generously leaving their central part to people.

Yes, rat bites no longer carry mortal danger, but still harm health. Children very often become victims of their bites. Annually, more than hundred bitten people enter the clinics of New York.

The characteristic of rodents only as pests is not entirely correct. Indeed, among them there are malicious pests that deserve to be exterminated by all possible means. But there are also such species, without which there would have been a catastrophic imbalance in the vital activity of many ecological systems. And many mouse-shaped rodents play the role of experimental animals in laboratories.

Thus, rodents, whose names are so diverse, and the numbers are so great, are very different in their significance, bringing to the life of man and the planet both catastrophic harm and colossal benefits.