Currently, there are over 44,000 species of spiders and only an expert can accurately determine a particular species by looking at the anatomy of a spider under a microscope. But if you familiarize yourself with the characteristic features of spiders, your guesses about the spider met will become more accurate. Unless, of course, you are scared and take a good look at that large, hairy spider in your bathroom (or tiny in your basement) and determine its physical features and habits. Most likely, you will be relieved to find out that this or that spider is not at all dangerous.
Blood circulation and respiration Edit
The heart carries 3-4 ostia. The terminal branches of the arteries pour hemolymph into the lacunae system, that is, between the internal organs, from where it enters the pericardial portion of the body cavity, and then through the ostia in the heart. Arachnoid hemolymph contains a respiratory pigment - hemocyanin.
The respiratory system of spiders is quite peculiar. They have lung bags that look like pages of a book, since there are plates. Open with breathing holes covered with covers. There are also regular tracheas that look like long tubes and transport oxygen through the respiratory openings (spiracles) to the tissues of the organs.
Nutrition, digestion and excretion Edit
All spiders are predators, feed mainly on insects. At the same time, more than 60 species of spiders belonging to 10 families were observed for occasional consumption of plant foods, mainly pollen and nectar. Many spiders catch prey using the web. Having caught prey, the spider kills it with poison and injects digestive juices into it. After some time (usually several hours), the spider sucks out the resulting nutrient solution.
Spiders have several sensory organs to sense the environment in which they live. Spiders have no ears. The spider hears with the help of tiny hairs of thrichobotria located on its legs. With the help of hairs, a spider is able to very accurately determine the place of sound emission, interpreting the movement of air produced by this sound.
The eyes of spiders of different families are very different. Spiders that hunt without a web of prey, like wolf spiders (Lycosidae), lynx spiders (Oxyopidae), and horse spiders (Salticidae), have very well-developed vision. Horse spiders can see almost as well as humans. Experiments have shown that they can even distinguish colors. Cave spiders that live in the dark do not see at all or see very poorly. They are completely dependent on sounds and sensations.
Orbiting spiders, for example, Araneus diadematus, have very small eyes. They practically do not need eyesight to catch prey. They have a very well developed sense mechanism, which helps to detect movements in their networks.
Spiders smell using special sensitive hair located on their legs. There is no taste sensation in the spider's mouth. The spider senses whether its prey is edible, using chemically sensitive hairs located on its legs.
Silk Production Edit
The web is more than 50% composed of fibroin protein with a molecular weight of 200-300 kDa. The web is made for various purposes: to build hunting nets and cocoons for eggs, flight in case of danger, etc. Six types of glands are known:
- glandula aggregata - produces sticky silk,
- glandula ampulleceae - the main and youngest for the production of threads for movement,
- glandula pyriformes - produces silk for fixing threads,
- glandula aciniformes - produces silk for braiding prey,
- glandula tubiliformes - produces silk for an egg bag,
- glandula coronatae - produces yarns for sticky yarn axes.
In a separate species of spiders, all types of glands do not occur simultaneously.
The web is an elastic material that breaks only when stretched 200-400%. Spiders often reuse spider web silk, eating trapping threads damaged by rain, wind, or insects. It is digested with the help of special enzymes.
Growth and Shedding Edit
Like all arthropods, spiders have a solid exoskeleton, which is almost not able to stretch as the animal grows (with the exception of the soft abdomen). Therefore, in order to grow, they need to periodically discard the old chitinous shell, instead of which a new larger one appears. Depending on the species, spiders can molt from 5 to 10 times in a lifetime. With age, the frequency of links decreases.
Before molting, spiders leave their shelters and refuse food. Legs and abdomen become darker. A new exoskeleton forms under the old.
Spiders are dioecious. Males are often smaller and more colorful than females. Males can be easily identified by pedipalps, or rather, by the oblong bulbs at their ends, which they use to enter sperm into the open genitals of female individuals.
Spider reproduction organs are located in front of the spinning organs. Males have various ways of showing a female that he is interested in mating. Some species of males offer a present, others “clink” their feet on the female’s net, and some perform a dance. If the signals are correct and the female is ready for pairing, she allows the cavalier to approach. Before mating, the males fill oblong bulbs (cymbiums) at the ends of the pedipalps with sperm, for which they create a small network. Then the males drop a few drops of sperm from the genitals onto the net and collect the sperm into the cymbiums.
After mating, there are frequent cases of devouring by a female male (see cannibalism of spiders).
The length of the body of different representatives varies significantly: from fractions of a millimeter to almost a dozen centimeters. The smallest spider - Patu digua reaches only 0.37 mm. The largest spiders are Blond's teraphosis tarantulas, whose body length can reach 9 cm, and leg span - up to 25 cm.
Spiders have only three types of pigments (visual pigments (English ommochrome), bilins and guanines), perhaps there are still undiscovered ones. Melanins, carotenoids and pterins, which are common among animals, are absent in spiders. In some species, the exocuticles of the paws and abdomen are formed by tanning and as a result they become brown. Bilins provide a brown color. Guanines are responsible for the white color, for example, in the cross (Araneus diadematus) Such births as: Tetragnatha, Leucauge, Argyrodes and Ther>. There are many species that have special flakes called guanicites. Structural colors in some spiders appear as a result of refraction, scattering, or interference of light, for example, modified flake bristles. White millet in representatives of the genus Argiope Is the result of the reflection of light by hairs, Lycosa and Josa there are parts of the body consisting of modified bristles that have the property of reflectors.
Spiders live all over the globe, but in the warm regions there are the most species. Almost all spiders are terrestrial animals. The exception is the silver spider, which lives in the water. A number of species of spiders prey on the surface of the water. Some spiders build nests, shelters and burrows, while others do not have a permanent habitat. Most spiders are nocturnal animals.
Detachment Spiders includes two suborders:
According to the World Spider Catalog, on August 8, 2017, the order is divided into 37 superfamilies, 112 families, 4057 genera and 46 806 species. Eleven families have an indefinite position - which means that their placement in superfamilies is possibly erroneous.
|Suborder / Infraorder||Superfamilies||Families||Childbirth||Species|
|Opisthothelae: Araneomorphae||26||95||3 696||43 834|
|Opisthothelae: Mygalomorphae||11||16||353||2 875|
The most ancient finds date from the Carboniferous period. The main material on the paleontology of spiders is represented by inclusions in amber. Often in such remains scenes from the life of spiders are captured: mating, catching prey, weaving a web, perhaps even taking care of the offspring. In addition, egg cocoons and hunting nets (sometimes with prey) are found in amber inclusions, the oldest known fossil web is about 100 million years old.
Most species of spiders bite people only in the event of defense, and only a few species can do more harm than a mosquito or a bee. According to some reports, the bite of a large cross is no less painful than the sting of a scorpion. Only some spiders are deadly to humans. Of the spiders living in Russia, karakurt.
In Cambodia and among the Piaroa Indians from southern Venezuela, fried tarantulas are considered a delicacy. Before preparing the tarantula, its burning hairs are removed.
Tarantulas are also widely used as exotic pets.
The poison of most spiders, fatal to insects and harmless to vertebrates, pollutes less, therefore, is an alternative to conventional pesticides. So, Australian spiders from the family Atracinae They produce poison, against which most of the insect pests common on Earth do not have immunity. These spiders feel great in captivity and easily give a poisonous “milk”. The spider genes responsible for the production of toxins can, through genetic engineering, be introduced into the genome of viruses that infect certain types of crop pests.
The possible use of spider venom for medical purposes for the treatment of cardiac arrhythmia, Alzheimer's disease, stroke and erectile dysfunction is being investigated.
Since the cobweb (“spider silk”) has a beautiful sheen, is very strong and wear-resistant, attempts are being made to make it, using genetic engineering, from goat milk and from plant leaves. Transparent web fibers are used by physicists working on optical communication systems to obtain a diffraction pattern on an interferogram in an N-slit interferometer.
Arachnophobia - a special case of zoophobia, fear of arthropods (mainly arachnids), is one of the most common phobias. Moreover, for some people, even the spider itself can cause a much greater fear, but the image of the spider.
In cinema, images of spiders are often used, for example, Spider-Man, Spiders (2000), Charlotte's Web, etc. In the Lord of the Rings movie trilogy, the image of the giant spider Shelob was made in appearance - Porrhothele antipodiana.