A new study suggests that the first mygalomorph spiders appeared under the feet of dinosaurs about 120 million years ago. They then slowly spread around the world thanks to continental drift.
Tarantula spiders form an infraorder of spiders, which currently includes fifteen families, 321 genera and 2,651 species. You will find them everywhere except Antarctica, from the American continents to Africa, through Asia, Europe and Oceania. But one question has tormented researchers for a long time: how did they spread so much?
Females and juveniles rarely leave their burrows, while mature males travel only when looking for a mate. Thus, this behavior makes them more of a “homebody.”
Who is a spider: introduction
Spider.
Spiders are the eternal neighbors of people. Their role is often underestimated, considering them unpleasant creatures. But their role in nature is very great. There is a whole science, arachnology, that studies this type of animal.
Spiders are representatives of the Arthropod phylum, Arachnida class. Currently there are more than 42 tons of species and more than 1000 fossils.
There is a recognized disease - arachnophobia. Moreover, for the most part, people cannot explain the reason for their fear. Experts believe that it is associated with childhood trauma. Symptoms appear: headache, fainting, nausea and the desire to run.
Arachnophobia is one of the most common and difficult to treat diseases.
Spiders of Russia.
Internal structure of arachnids
The respiratory system of the cross spider is represented by pulmonary sacs and trachea. The pulmonary sacs and trachea of arachnids open outwards with special openings on the lateral parts of the segments. The pulmonary sacs contain numerous leaf-shaped folds in which blood capillaries pass.
The trachea is a system of branched tubes that connect directly to all organs where tissue gas exchange takes place.
The circulatory system of arachnids consists of a heart located on the dorsal side of the abdomen and a vessel through which blood moves from the heart to the front of the body. Since the circulatory system is not closed, blood returns to the heart from the mixed body cavity (mixocoel), where it washes the lung sacs and trachea and is enriched with oxygen.
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The excretory system of the cross spider consists of several pairs of tubes (Malpighian vessels) located in the body cavity. Of these, waste products enter the posterior intestine.
The nervous system of arachnids is characterized by the fusion of nerve ganglia with each other. In spiders, the entire nerve chain merges into one cephalothoracic ganglion. The organ of touch is the hairs covering the limbs. The organ of vision is 4 pairs of simple eyes.
Order Arthropods
Arthropods are a group that accounts for more than 80% of the planet's living creatures. Their difference is an exoskeleton made of chitin and paired jointed limbs.
The ancestors of arthropods are considered to be either worm-like or tracheal. However, there is an opinion that all representatives came from one ancestor - nematodes.
Representatives of arthropods.
One of the most famous classifications of origin divides them into three types:
- Tracheal;
- Crustaceans;
- Cheliceraceae.
Tracheal
This group of arthropods have respiratory organs, which made them adapted to life on land. The respiratory system has been improved, and the skin has been strengthened.
There are several representatives of this species.
A superclass of invertebrates that has a segmented body. They have a large number of legs and a body that is not divided into sections.
Centipedes
This is a subphylum that includes a wide variety of insects. According to the name, the number of their limbs is six. Lifestyle and nutrition are different.
Hexapods
Crustaceans
This group contains a large number of animals that live in various types of reservoirs. Although there are some species that can live on land or in humid conditions.
They have a chitinous exoskeleton that is periodically shed and their respiratory organs are gills. The group includes:
- crabs;
- lobsters;
- shrimps;
- crayfish;
- krill;
- lobsters.
Cheliceraceae
Cheliceraceae.
The largest part of this subgroup is represented by arachnids. These also include ticks and crustacean scorpions. They have a specific role in nature and for humans.
The subclass got its name from its limbs, chelicerae. These are oral appendages that are divided into two or three segments. But they are not designed for eating tough foods.
External structure and nutrition of arachnids
In spiders, the body segments merge to form the cephalothorax and abdomen, separated by an interception.
The body of arachnids is covered with a chitinized cuticle and underlying tissue (hypodermis), which has a cellular structure. Its derivatives are arachnoid and poisonous glands. The venom glands of the cross spider are located at the base of the upper jaws.
A distinctive feature of arachnids is the presence of six pairs of limbs . Of these, the first two pairs - the upper jaws and the tentacles - are adapted for capturing and grinding food. The remaining four pairs perform the functions of movement - these are walking legs.
During embryonic development, a large number of limbs are formed on the abdomen, but later they are transformed into arachnoid warts , opening by the ducts of the arachnoid glands. Hardening in air, the secretions of these glands turn into spider threads, from which the spider builds a trapping network.
After the insect has fallen into the net, the spider envelops it in a web, plunges the claws of its upper jaws into it and injects poison. Then he leaves his prey and hides in cover. The secretion of the poisonous glands not only kills insects, but acts as digestive juice. After about an hour, the spider returns to its prey and sucks out the semi-liquid, partially digested food. From a killed insect, only one chitinous cover remains.
Insects and spiders
These two types of arthropods are often confused. But they have much more differences than they have in common. Among insects, there are those that eat meat and those that are vegetarians. Spiders are mostly predators.
Spiders are definitely not insects! More differences in the structure and behavior of insects and spiders in the article at the link.
Spider Anatomy
Spider eyes
The number of eyes is not an indicator of good vision. And spiders are a prime example of this.
Spider legs
The limbs perform not only a walking role. They help in hunting.
Spider Reproduction
The method of reproduction of spiders is determined by their lifestyle and structural features.
These hairy creatures
Some people hate spiders. Perhaps because they are hairy. Tarantulas are the hairiest of all spiders. They use their hair as a defense mechanism. They can brush away clouds of belly hair with their hind paws. Each hair is covered with hundreds of microscopic hooks that cause itching when in contact with the skin, especially in the nose and eye areas.
The spider's legs are covered with hair. Each hair, in turn, can have up to 1000 extensions. About 160,000 contact points allow spiders to walk perpendicularly or upside down on glass.
Like humans, spiders' behavior is controlled by the central nervous system. To feed themselves, spiders rely on mechanoreceptors such as touch, vibration and air currents. Spiders have a sense of taste and smell, and they exhibit the ability to learn.
Most spiders are active at night and rely on touch and scent to help them find mates and recognize prey and predators. More than 1,000 hairs on the front of the legs are sensitive to chemical odors.
What types of spiders are there?
Large pink tarantula.
There are more than 40 thousand species of spiders. They can live in grass, near human habitation and in remote places.
There are very miniature spiders, but there are also large representatives that do not fit on a plate. But all species have the same structure.
Conventionally, types of spiders can be divided into:
- woody;
- domestic;
- safe;
- poisonous.
In Russia, according to the latest data, there are about 2,400 species. More and more of them are opened every year. They are distributed in different regions and climates.
A detailed acquaintance with the spider fauna of Russia.
Silk is stronger than bone
All spiders can produce silk. Spider silk is amazing. It is stronger than bones, tendons or cellulose (wood). Only steelmaking iron ore is stronger. Spider silk is strong because it is made up of multiple proteins and water, giving it incredible elasticity. A spider's silk thread must be about 86 km long before it breaks under its own weight.
Only spiders, as their name suggests, produce webs or webs to capture prey. Ground spiders have to constantly wander in search of prey. Webs come in different types, such as sheet, frame or ball. The spider hides behind one end of the web, jumping out only when the prey is trapped.
Orb webs are commonly seen in yards and woods almost all over the world. Radial threads converge at a central location. The frame carving outlines the canvas and serves as the starting point for the radial carving. Both types of threads serve as support for the sticky gripping coil. The spider feels the vibration of the caught prey. Usually it can jump out along a precise radial thread leading directly to the insect.
Spiders are extraordinary engineers. In just half an hour at night, using the sense of touch rather than sight, they can weave 20 meters of silk net. The web weighs no more than 0.1–0.5 milligrams, but can easily hold a spider weighing more than 500 milligrams.
Spiders flourished in ancient forests of the Carboniferous period about 300 million years ago. The fossil record shows that nets were used 100 million years ago. About 300 species have been described since the Tertiary period from samples of well-preserved Baltic and Dominican amber (fossilized tree resin) from 40 million years ago. Spiders are worthy of our admiration; they have stood the test of time on our blue planet.
Interesting Facts
Spiders inspire fear in people, but at the same time they inspire interest. Therefore, they are studied and even raised at home as pets.
Flying spiders
There is evidence that some species of spiders can fly. And this is not to instill fear in the impressionable. This method is a protection and a method of movement.
Spiders with a tail
There were individuals that had a tail. Unusual tailed spiders and their descendants.
Web
Spider web is a strong and stable material; it can stretch several times and return to its original position.
True representatives of blue bloods
The blood (more correctly called hemolymph) of spiders is rich in copper pigments, giving it a bluish tint. Blood cells play an important role in blood clotting, wound healing, and fighting infections. One molecule of spider hemolymph contains more than 600 amino acids, or protein building blocks.
About 30 species of spiders contain poison that is lethal to humans. Black widows, Australian funnel-web spiders, American browns, two species of European water spiders and the aggressive South American ctenid spiders contain venom that attacks and disturbs the human central nervous system. If bitten, the person must take an antidote to avoid death.
However, in most cases, spider bites are much less dangerous to humans than the poisonous stings of bees, wasps and hornets.
The spider's venom is designed to paralyze its prey - mainly insects. Defensive bites against large animals, including humans, are secondary.
The poison is injected through the fangs. The spider crunches its prey either immediately after wrapping it in silk, or sucks out its innards through holes in its fangs - like a straw draining the last drop from a soda bottle.
Other arachnids
Central Asia and Africa are home to large arthropods, which are unknowingly confused with spiders. In fact, these are salpugs or, as they are also called, camel spiders. Unlike spiders, these living creatures do not have poisonous glands or glands for creating webs, but they are armed with teeth.
Spiders cause a feeling of fear in many people, but this is more likely due to ignorance. In fact, these are quite harmless living creatures.
Interesting classification
Everyone knows that there are lovers of large tarantula spiders who classify their favorites depending on their speed characteristics. For example:
- For Dummies" . These are slow-moving members of this species that many people like to film. They can sit quietly on the palm of a person and move extremely slowly.
- For the “advanced” . These arthropods move quite quickly, so it’s unlikely to be captured on video.
- For professionals . They move so quickly that it is unlikely to notice in which direction the arthropod disappeared.
If we take into account such speed characteristics, it is not difficult to imagine how many species humanity does not yet know about.
Types of web
There are several types of different webs in the world. They are:
- Round . The most common. It has a minimum number of threads. Because of this weaving, it is hardly noticeable, but it is not perfectly elastic every time. Radical threads-webs emanate from its center, which are connected by spirals with a sticky base.
- Cone-shaped . Basically, the funnel spider weaves it in tall grass, and, waiting for prey, it hides in its narrow base.
- Zigzag.
- Gigantic . Its dimensions vary from 900 to 28 thousand square centimeters.
