The nervous system of any living organism receives information about the environment through the senses. The arachnid class is no exception. In this article, we will talk in more detail about all the sense organs in arachnids, their meaning and location.
Sense organs of arachnids
Touch plays the most important role. In spiders, this organ is represented in the form of hairs (trichobothria), which are located throughout the body. Most of them are on pedipalps and walking legs. The structure of each hair is presented as follows:
- mobile hair attached to the bottom of the fossa on the integument of the body;
- in the fossa there is a group of sensitive cells with which the hair is connected.
Rice. 1. Organs of touch
Each oscillation of trichobothria accurately determines all types of mechanical movement. The organs of touch work so precisely that spiders easily catch the smallest swaying of the web or air, while distinguishing the nature of irritation.
Rice. 2 Spider Hair
The lyre-shaped organs, located on the surface of the whole body, perform the function of chemical sense organs. They are presented in the form of cracks on the body, in the depths of which sensitive cells are located. These are the so-called organs of smell. Taste-sensing cells are found on walking legs, leg tentacles, and the lateral part of the pharynx. However, these animals distinguish smells only at a close distance.
Organs of vision of arachnids
Compared to crustaceans, arachnids have a simple structure of the organs of vision. They are located in front of the cephalothorax and can be represented by three, four, less often one pair of eyes. The organs of vision of arachnids in each order and species are presented in their own way. So, for example, in scorpions, the median eyes are larger, and 2-5 pairs of smaller eyes are located on the sides. Spiders have four pairs of eyes arranged in two arcs. At the same time, the middle eyes of the anterior arch are larger than all the other eyes.
Fig.3. Eye location
Arachnids do not see very well. For example, scorpions of their own kind are distinguished only at a distance of 2-3 cm, and some types of spiders - at a distance of 20-30 cm.
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For some species of arachnids, vision plays a very important role. For example, jumping spiders with smeared eyes cease to distinguish between females and perform a dance characteristic of the mating season.
What have we learned?
Arachnids, like all animals, have sensory organs. The most important role for their life is played by touch. The eyes have a simple structure, despite their number, arachnids see poorly.
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The respiratory organs of Arachnida are varied. Some have lung sacs, others have tracheae, and others have both at the same time. Only lung sacs are found in scorpions, flagellates, and primitive spiders. In scorpions, on the abdominal surface of the 3rd - 6th segments of the anterior abdomen, there are 4 pairs of narrow slits - spiracles that lead to the lung sacs (Fig. 389). Numerous leaf-like folds parallel to each other protrude into the cavity of the sac, between which narrow slit-like spaces remain, air penetrates into the latter through the respiratory gap, and hemolymph circulates in the lung leaflets. The flagellated and lower spiders have only two pairs of lung sacs. In most other arachnids (solpugs, haymakers, false scorpions, some ticks), the respiratory organs are represented by tracheae (Fig. 399, Fig. 400). On the 1st - 2nd segments of the abdomen (in salpugs on the 1st segment of the chest) there are paired respiratory openings, or stigmas. From each stigma, a bundle of long, thin air tubes of ectodermal origin, blindly closed at the ends, extends into the body (they form as deep protrusions of the outer epithelium). In false scorpions and ticks, these tubes, or tracheas, are simple and do not branch; in haymakers, they form side branches.
Finally, in the order of spiders, both types of respiratory organs are found together. The lower spiders have only lungs; among 2 pairs they are located on the lower side of the abdomen. The rest of the spiders retain only one anterior pair of lungs, and behind the latter there is a pair of tracheal bundles (Fig. 400), which open outwards with two stigmas. Finally, one family of spiders (Caponiidae) has no lungs at all, and the only respiratory organs are 2 pairs of tracheas (Fig. 400).
The lungs and trachea of arachnids arose independently of each other. The lung sacs are undoubtedly more ancient organs. It is believed that the development of the lungs in the process of evolution was associated with a modification of the ventral gill limbs, which the aquatic ancestors of arachnids possessed and which were similar to the gill-bearing ventral legs of horseshoe crabs. Each of these limbs retracted into the body. At the same time, a cavity was formed for the lung leaflets (Fig. 401). The lateral edges of the stalk adhered to the body almost along its entire length, except for the area where the respiratory gap was preserved.
The abdominal wall of the lung sac, therefore, corresponds to the former limb itself, the anterior section of this wall corresponds to the base of the leg, and the lung leaflets originated from the gill plates located on the back of the abdominal legs of the ancestors. This interpretation is confirmed by the development of lung sacs. The first folded rudiments of the lung plates appear on the posterior wall of the corresponding rudimentary legs before the limb deepens and turns into the lower wall of the lung. The tracheae arose independently of them and later as organs more adapted to air breathing. In some small arachnids, including some mites, there are no respiratory organs, and breathing takes place through thin covers.
Question 1. What structural features are characteristic of representatives of the arachnid class?
Structural features of arachnids:
the body is divided into cephalothorax and abdomen;
no antennae;
on the cephalothorax 4 pairs of walking legs; two more pairs of limbs are transformed into pedipalps, which serve to capture and hold prey, and chelicerae - tools for grinding and crushing food;
there are no limbs on the abdomen;
there is an external chitinous skeleton;
respiratory organs can be of two types and be present together or separately: lung sacs and tracheae;
the excretory system is a pair of mostly branching Malpighian vessels - tubular tubules formed by protrusion of the midgut;
the circulatory system is not closed;
the nervous system is formed by the ventral nerve cord; supraesophageal ganglion, has a more complex structure than that of crustaceans;
eyes are simple.
Question 2. What departments does the body of a spider consist of; scorpion?
The body of the spider consists of a non-segmented cephalothorax and abdomen, connected by a thin stalk.
In the body of a scorpion, a cephalothorax and an abdomen, consisting of segments, are distinguished.
Question 3. How many limbs does a spider have? What are they called and what function do they perform?
The cephalothorax bears six pairs of limbs. Chelicerae - the first pair of limbs, consisting of 2-3 segments, ending in a claw, hook or stylet. Pedipalps (mandibles, leg tentacles) - the second pair of limbs - can perform several functions: the organ of touch, the lower jaw, walking legs, claws for capturing food; males may use them as a copulatory apparatus. The last four pairs of limbs are walking legs. The legs of spiders end in comb claws, which are necessary for making webs. The abdominal limbs have been transformed into spider warts.
Question 4. What sensory organs does a spider have?
Mechanical tactile stimuli, which are very important for arachnids, are perceived by differently arranged sensory hairs, which are especially numerous on the pedipalps. The organs of vision are represented by simple eyes; spiders most often have 8 eyes.
Question 5. How does the development of arachnids?
In the vast majority of arachnids, development is direct. Only ticks develop with metamorphosis. (Metamorphosis is a deep transformation of the structure of the body, during which the larva turns into an adult.) Arachnids have separate sexes. There is sexual dimorphism. In arachnids, internal fertilization appeared (due to the terrestrial lifestyle). The male pedipalp injects sperm into the female's seminal receptacles, the spermatozoa fertilize the eggs in the uterus, located in the abdomen. Most arachnids lay large, yolk-rich, cocoon-protected eggs. Embryonic development takes place in the cocoon, after which small spiders emerge from the cocoon.
Question 6. Make a table "Comparative characteristics of crustaceans and spiders" (work in small groups).
Comparative characteristics of crustaceans and spiders
Question 7. Describe the medical significance of ticks.
Most mites of medical importance are blood-sucking. Animals - hosts of ticks are mammals, birds and reptiles.
Together with the host’s blood, pathogens of various diseases penetrate into the tick’s body, which, when switching to another host, can be transmitted to it, which contributes to the circulation of pathogens. The life of ticks is quite long - from 6 months to 20-25 years.
Tick saliva has a local irritant and general toxic effect. Mass attacks of ticks can cause not only skin lesions, but also severe febrile conditions and nervous disorders. Of particular danger is the ability of ticks to be carriers of pathogens.
From the point of view of medicine, ticks of the Ixodes and Argas families, as well as the scabies mite of the Acariform family, are of the greatest importance from the point of view of medicine.
Question 8. What is the essence of partially external digestion in spiders?
Digestion in spiders is partially extracavitary. Therefore, in a complex digestive system, with many specialized departments, they are not necessary. In the digestive system of spiders, a pharynx and an intestine, which ends with an anus, are distinguished. The spider injects the secret of the salivary glands into the body of the killed prey, which has the ability to break down proteins. There is an external (outside the body of the spider) digestion of food into a liquid slurry, which is then absorbed by the spider.
Squad: Araneae = Spiders
Read more: Curious Facts About Spiders
The central nervous system of spiders is highly concentrated. The sense organs play an important role in their complex life. Prevailing importance, especially in the tenet forms, is the sense of touch. The trunk and appendages are covered with numerous tactile hairs. Hairs of a special structure - trichobothrium are found on the pedipalps and legs. There are up to 200 of them. With the help of trichobothria, the spider feels the most insignificant puffs of air, for example, from a flying fly. Trichobothria perceive rhythmic vibrations in a wide range of frequencies, but not directly as sound, but through the vibration of cobweb threads, that is, as tactile sensations. If you touch the web of a cross-spider with a sounding tuning fork, the spider will head towards it as if it were prey. However, the sound of the tuning fork not touching the web puts the spider to flight. It is believed that the sound is perceived by some other organs. It is known that spiders often enter the network at the sound of a musical instrument, such as a violin. With such a positive reaction, obviously, there is not an auditory, but a tactile sensation of the resonating threads of the web.
Another kind of tactile sense is the perception of the degree of tension of the web threads. When their tension changes in the experiment, the spider seeks its shelter, always moving along the most tense threads. The crosser runs much more quickly towards a heavy object that has fallen into the net than towards a light one. 
The organs of balance and hearing are unknown in spiders, but they have these senses. Having mastered the prey, the spider returns to the center of the web. If you place a fly in a net above the center, the spider will move upward towards it. Turning the web 90 or 180° can disorient the spider. Having finished with the fly, he begins to descend the net, as if to its center, and finds himself at the edge of the net. In this case, the feeling of heaviness and: balance prevails over the changed tactile sensations.
The presence of hearing in spiders is confirmed by a number of facts. Lycosid spiders react to the buzzing of a hidden fly that they cannot see, araneids raise their front legs to the sound of a certain tone. Some spiders make sounds, and in some cases their role in attracting sexes has been proven. Sound organs are stridulators, i.e. surfaces rubbing against each other with ribs or rows of setae. They occur on chelicerae and pedipalps or only on chelicerae, on contiguous parts of the cephalothorax and abdomen, and in other places. The sound apparatus is either only males, or both sexes. The latter is observed in some migalomorph spiders, which have rows of special setae (comb and lyre) on their chelicerae and pedipalps. The spider quickly rubs them against each other. The sounds made by small spiders (family Theridiidae, Linyphiidae, etc.) are very weak and are recorded only by special devices. Their height is 325-425 vibrations per second. Some migalomorphic spiders make sounds audible to humans - crackling, buzzing, hissing. In a number of cases, the sound is combined with a threat posture and apparently has a warning value.
The organs of smell are the tarsal organs on the tarsi of the forelegs and the lyre-shaped organs, which are present in large numbers on the trunk and appendages. Spiders distinguish the smells of volatile substances, but usually react at a close distance from the source of the smell. Males distinguish the tenet of a sexually mature female from the tenet of an immature female by smell. The role of smell in this case has been proven experimentally. If an ethereal extract is made from the cobweb or the torn off leg of a sexually mature female and poured into a saucer, then after the evaporation of the ether, the male planted in the saucer exhibits characteristic sexual arousal. The tarsal organs also serve as taste organs, with their help the spider in the experiment distinguishes between pure water and solutions of various substances. Apparently, these organs play a role in finding the drinking water needed by some spiders. Sensitive taste cells are found in the walls of the throat of spiders. In the experiment, spiders well distinguish pieces of elderberry core soaked in a nutrient solution from the same pieces soaked in water. The first are sucked out, and the second are removed from the nets.
The vision of spiders is imperfect, especially in the tenet forms. Stray spiders see better, especially active during the day. The eye is usually four pairs. The front medial eyes, called the main ones, are dark; the rest, secondary eyes, usually shiny due to the inner shell (mirror) reflecting light. The size and mutual position of the eyes are different in different systematic groups of spiders. More often they form two transverse rows, but they are arranged differently. Sometimes individual pairs of eyes are enlarged, for example, the four anterior eyes in jumping spiders, the medial posterior eyes in Dinops (family Dinopidae). In some cases, the number of eyes is reduced to six, four or two. Among the cave spiders there are blind ones. The eyes of web spiders are located so that they cover a large field of view, but they mainly distinguish between the strength and direction of light, capturing the movement of large objects. Many spiders sitting on nets notice an approaching person and fall on a web of thread. With a sharp change in the usual lighting of surrounding objects, mink spiders lose their orientation and cannot immediately find their lair. Side-walker spiders (family Thomisidae), lying in wait for prey on flowers, notice a cabbage butterfly at a distance of 20 cm, and a fly only at a distance of 3 cm. but do not distinguish the era form.
A kind of exception is represented by small jumping spiders (family Salticidae). Their long-focus main eyes produce a large image on the retina with a small field of view (as in a camera with a telephoto lens). Unlike other eyes, the visual elements of the retina are densely located here, due to which the vision is objective: at a distance of 8 cm, the spider sees the fly in detail. The small field of view of these eyes is compensated by a remarkable feature: they can move with the help of special muscles. The spider follows its prey with its eyes - a rare example among terrestrial arthropods. Side eyes do not distinguish the shape of objects, but are located in such a way that the spider notices any movement in front, behind itself and above itself. The anterior lateral eyes have a total binocular field of view of about 40°, due to which the spider perceives the volume of objects and the distance to them. The eyes of horses act as a single visual apparatus. If a fly approaches the spider from behind, it notices its movement with its rear eyes at a distance of 20-25 cm and turns towards it so that it enters the field of view of the front eyes. Now it is perceived more clearly and in space. Then the spider catches it with its main eyes, perceives it in close-up and begins to follow it with its eyes. At a distance of 8 cm, the object is recognized as prey, from 4 cm the spider begins to creep up and from 1.5 cm jumps at the fly with lightning speed with such accuracy that it rarely misses. Good vision of horses helps them to move in the grass, deftly jumping from leaf to leaf. With the help of the eyes, the male detects the female, and being blinded, does not recognize her and does not perform his characteristic mating dances. Placed in front of a mirror, the male racer reacts to his image as a rival, assumes a pose of threat or rushes at him.
Steeds and some other spiders distinguish the color of objects. This was established by several methods, including the development of conditioned reflexes. The spiders were exposed to flies under red and blue, and under red and green light. Red lighting was accompanied by electric shock irritation. After several repetitions of the experiment, the spider took the fly only under blue or green light. ....
distinguish at least 12 detachments, the most important of which are the detachments of Spiders, Scorpions, False Scorpions, Solpugs, Haymakers, Ticks.
Arachnids are distinguished by the fact that they lack antennae (antennales), and the mouth is surrounded by two pairs of peculiar limbs - chelicerae and mandibles, which in arachnids are called pedipalps. The body is divided into the cephalothorax and abdomen, but in ticks all sections are fused. walking legs four couples.
cross spiders these are ordinary representatives of the class Arachnida. cross spiders this is the collective name of several biological species of the genus Araneus of the family Orb-weaving spiders of the order Spiders. Cross-spiders are found in the warm season everywhere in the European part of Russia, in the Urals, in Western Siberia.
Cross spiders are predators that feed only on living insects. The spider-cross catches its prey with the help of a very complex, vertically located wheel-shaped trapping net(hence the name of the family - Orb-weaving spiders) . The spinning apparatus of spiders, which ensures the manufacture of such a complex structure, consists of external formations - arachnoid warts- and from the internal organs - spider glands. A drop of sticky liquid is released from the spider warts, which, when the spider moves, is drawn into the thinnest thread. These threads quickly thicken in the air, turning into a strong gossamer thread. The web is made up mainly of protein. fibroin. In terms of chemical composition, the web of spiders is close to the silk of silkworm caterpillars, but is more durable and elastic. The tensile load for the web is 40-261 kg per 1 sq mm of the thread section, and for silk it is only 33-43 kg per sq mm of the thread section.
To weave its trapping web, the Spider-cross first stretches especially strong threads in several places convenient for this, forming a supporting frame for the future network in the form of an irregular polygon. Then he moves along the upper horizontal thread to its middle and, going down from there, draws a strong vertical thread. Further from the middle of this thread, as from the center, the spider conducts radial threads in all directions, like the spokes of a wheel. This is the basis of the entire web. Then the spider starts spinning from the center spiral threads, attaching them to each radial thread with a drop of adhesive. In the middle of the web, where the spider itself then sits, the spiral threads are dry. Other spiral threads are sticky. Insects that fly onto the net stick to them with their wings and paws. The spider itself either hangs head down in the center of the web, or hides in
Class Arachnids Cross-spider
side under the leaf - there he has refuge. In this case, he stretches a strong signal a thread.
When a fly or other insect enters the net, the spider, feeling the signal thread trembling, rushes out of its ambush. By thrusting the claws of the chelicera with poison into the victim, the spider kills the victim and secretes digestive juices into her body. After that, he entangles a fly or other insect with a web and leaves it for a while.
Under the influence of the secreted digestive juices, the internal organs of the victim are quickly digested. After some time, the spider returns to the victim and sucks out all the nutrients from it. From the insect in the web, only an empty chitinous cover remains.
Making a trapping net is a series of interconnected unconscious actions. The ability to do so is instinctive and inherited. This is easy to verify by following the behavior of young spiders: when they emerge from the eggs, no one teaches them how to weave a trapping net, the spiders immediately weave their web very skillfully.
In addition to the wheel-shaped trapping net, other types of spiders have nets in the form of a random weave of threads, nets in the form of a hammock or canopy, funnel-shaped nets and other types of trapping nets. The trapping web of spiders is a kind of adaptation outside the body.
I must say that not all types of spiders weave trapping nets. Some actively search for and catch prey, others lie in wait for it from an ambush. But all spiders have the ability to secrete webs, and all spiders are made from webs. egg cocoon and spermatic nets.
External structure. The body of the Spider-cross is divided into cephalothorax and abdomen, which connects to the cephalothorax with a thin movable stalk. There are 6 pairs of limbs on the cephalothorax.
First pair of limbs chelicerae, which surround the mouth and serve to capture and puncture prey. Chelicerae consist of two segments, the final segment has the form of curved claws. At the base of the chelicerae are poison glands, whose ducts open at the tips of the claws. With chelicerae, spiders pierce the covers of victims and inject poison into the wound. Spider venom has a nerve-paralytic effect. In some species, for example, Karakurt, near the so-called tropical black widow, the poison is so strong that it can kill
Class Arachnids Cross-spider
even a large mammal (instantly!).
Second pair of cephalothoracic limbs pedipalps have the appearance of jointed limbs (they look like short legs sticking forward). The function of pedipalps is to feel and hold prey. In sexually mature males, the pedipalp is formed on the terminal segment copulatory apparatus, which the male fills with sperm before mating. During copulation, the male, using the copulatory apparatus, injects sperm into the female's seminal receptacle. The structure of the copulatory apparatus is species-specific (that is, each species has a different structure).
All arachnids have 4 pairs walking legs. The walking leg consists of seven segments: coxa, swivel, hips, cups, shins, pretarsus and paws armed with claws.
Arachnids have no antennae. On the front of the cephalothorax, the Cross-Spider has two rows of eight simple eyes. Other types of eyes may have three pairs, and even one pair.
Abdomen in spiders, it is not segmented and does not have true limbs. On the abdomen is a pair of lung sacs, two beams trachea and three couples gossamer warts. The spider warts of the Spider-Spider consist of a huge number (about 1000) gossamer glands, which produce various types of cobwebs - dry, wet, sticky (at least seven varieties of the most different purposes). Different types of webs perform different functions: one is for catching prey, another is for building a dwelling, and the third is used in the manufacture of a cocoon. Young spiders also settle on cobwebs of a special property.
On the ventral side of the abdomen, closer to the junction of the abdomen with the cephalothorax, sexual hole. In females, it is surrounded and partially covered by a chitinous plate. epigyna. The structure of the epigyne is species-specific.
Body covers. The body is covered with chitinous cuticle. The cuticle protects the body from external influences. The most superficial layer is called epicuticle and it is formed by fat-like substances, therefore the covers of spiders are not permeable to either water or gases. This allowed the spiders to colonize the most arid regions of the globe. The cuticle simultaneously performs the function
Class Arachnids Cross-spider
outdoor skeleton: Serves as a site for muscle attachment. Spiders molt periodically, i.e. shed the cuticle.
musculature arachnids consists of striated fibers that form powerful muscle bundles, i.e. the musculature is represented by separate bundles, and not by a bag like in worms.
body cavity. The body cavity of Arachnids is mixed - mixocoel.
Digestive system typical, consists of front, middle and rear intestines. The foregut is represented mouth, throat, short esophagus and stomach. The mouth is surrounded by chelicerae and pedipalps, with which spiders grab and hold prey. The pharynx is equipped with strong muscles for the absorption of food gruel. Ducts open into the foregut salivary glands, the secret of which effectively breaks down proteins. All spiders have the so-called extraintestinal digestion. This means that after killing the prey, digestive juices are introduced into the body of the victim and the food is digested outside the intestines, turning into a semi-liquid slurry, which is absorbed by the spider. In the stomach, and then in the middle intestine, food is absorbed. The midgut has long blind lateral protrusions, which increase the area of absorption and serve as a place for temporary storage of food mass. This is where the ducts open. liver. It secretes digestive enzymes and also ensures the absorption of nutrients. Intracellular digestion takes place in the liver cells. At the border of the middle and posterior sections, the excretory organs flow into the intestine - malpighian vessels. The hindgut ends anal hole located at the posterior end of the abdomen above the arachnoid warts.
Respiratory system. Some arachnids have respiratory organs pulmonary bags, other's tracheal system, the third - both those and others at the same time. Some small arachnids, including some mites, have no respiratory organs, breathing is carried out through thin covers. The lung sacs are more ancient (from an evolutionary point of view) formations than the tracheal system. It is believed that the gill limbs of the aquatic ancestors of arachnids plunged into the body and formed cavities with lung leaflets. The tracheal system arose independently and later than the lung sacs, as organs more adapted to air breathing. The tracheae are deep protrusions of the cuticle into the body. The tracheal system is perfectly developed in insects.
Class Arachnids Cross-spider
In the Cross-Spider, the respiratory organs are represented by a pair lung sacs, forming leaf-like folds on the ventral side of the abdomen, and two bundles trachea that open spiracles also on the underside of the abdomen.
circulatory system open, consists of hearts, located on the dorsal side of the abdomen, and several large blood vessels extending from it vessels. The heart has 3 pairs of ostia (holes). From the anterior end of the heart anterior aorta disintegrating into arteries. Terminal branches of arteries pour out hemolymph(this is the name of the blood in all arthropods) into the system cavities located between the internal organs. Hemolymph washes all internal organs, delivering nutrients and oxygen to them. Further, the hemolymph washes the lung sacs - gas exchange occurs, and from there it enters pericardium, and then through ostia- in the heart. The hemolymph of arachnids contains a blue respiratory pigment - hemocyanin, containing copper. Pouring into the secondary body cavity, the hemolymph mixes with the secondary cavity fluid, therefore they say that arthropods have a mixed body cavity - mixocell.
excretory system in arachnids is represented malpighian vessels, which open into the intestine between the midgut and hindgut. Malpighian vessels, or tubules, are blind protrusions of the intestine that provide absorption of metabolic products from the body cavity. In addition to Malpighian vessels, some arachnids also have coxal glands- paired saccular formations lying in the cephalothorax. Convoluted canals depart from the coxal glands, ending urinary bubbles and output ducts, which open at the base of the walking limbs (the first segment of the walking legs is called coxa, hence the name - coxal glands). The spider-cross has both coxal glands and malpighian vessels.
nervous system. Like all Arthropods, Arachnids have a nervous system - ladder type. But in Arachnids, there was a further concentration of the nervous system. A pair of supraesophageal nerve ganglia is called the "brain" in arachnids. It innervates (governs) the eyes, chelicerae and pedipalps. All cephalothoracic nerve ganglia of the nerve chain merged into one large nerve ganglion located under the esophagus. All abdominal nerve ganglia of the nerve chain also merged into one large abdominal ganglion.
Of all the sense organs, the most important for spiders is touch. Numerous tactile hairs - trichobothria- scattered in large numbers over the surface of the body, especially on the pedipalps and walking legs.
Class Arachnids Cross-spider
Each hair is movably attached to the bottom of a special hole in the integument and is connected to a group of sensitive cells located at its base. The hair perceives the slightest vibrations of the air or the web, sensitively reacting to what is happening, while the spider is able to distinguish the nature of the irritating factor by the intensity of the vibrations. Tactile hairs are specialized: some register chemical stimuli, others - mechanical, others - air pressure, fourth - perceive sound signals.
The organs of vision are represented simple eyes found in most arachnids. Spiders usually have 8 eyes. Spiders are myopic, their eyes perceive only light and shadow, the outlines of objects, but details and color are not available to them. There are organs of balance - statocysts.
Class Arachnids Cross-spider
performs copulation. The female at this moment is good-natured and relaxed. But, immediately after mating, the male must hastily leave, since the behavior of the spider after copulation changes dramatically: it becomes aggressive and very active. Therefore, slow males are often killed by the female and eaten. (Well, after mating, the male will still die. From an evolutionary point of view, the male is no longer needed: he has fulfilled his biological function.) This happens in almost all species of spiders. Therefore, in studies, females are most often found, while males are rare.
After copulation, the female continues to feed actively. In autumn, a female from a special web makes cocoon in which it lays several hundred eggs. She hides the cocoon in some secluded place, for example, under the bark of a tree, under a stone, in the cracks of a fence, etc., and the female herself dies. Cross-spider eggs overwinter. In the spring, young spiders emerge from the eggs, which begin an independent life. Shedding several times, the spiders grow and reach sexual maturity by the end of summer and start breeding.
reproduction and development. arachnids separate sexes. Fertilization internal. Most arachnids lay eggs, but live births have been observed in some arachnids. Development without metamorphosis.
The Cross-Spider has a well-defined sexual dimorphism: the female has a large abdomen, while mature males develop on pedipalps copulative bodies. In each species of spider, the copulatory organs of the male approach the epigyne of the female like a key to a lock, and the structure of the copulatory organs of the male and the epigyne of the female is species-specific.
Cross-spiders mate in late summer. Sexually mature males of trapping nets do not weave. They wander in search of the webs of females. Having found the trapping net of a sexually mature female, the male somewhere aside on the ground, or on some twig, or on a leaf weaves a small spermatic reticulum in the form of a hammock. On this mesh, the male from his genital opening, which is located on the ventral side of the abdomen closer to the junction of the abdomen with the cephalothorax, squeezes out a drop sperm. Then he sucks this drop into the pedipalps (like a syringe) and proceeds to seduce the female. The spider's eyesight is weak, so the male needs to be very careful so that the female does not mistake him for prey. To do this, the male, having caught some insect, wraps it in a web and presents this kind of gift to the female. Hiding behind this gift as a shield, the male very slowly and very carefully approaches his lady. Like all women, the spider is very curious. While she is looking at the presented gift, the male quickly climbs onto the female, puts his pedipalps with sperm on the female's genital opening and
Meaning. The role of spiders in nature is great. They act as second-order consumers in the ecosystem structure (i.e. consumers of organic matter). They destroy many harmful insects. They are food for insectivorous birds, toads, shrews, snakes.
Questions for self-control
Name the classification of the phylum Arthropoda.
What is the systematic position of the Spider-cross?
Where do cross spiders live?
What body shape do cross spiders have?
What is the body of a spider covered with?
What body cavity is characteristic of a spider?
What is the structure of the digestive system of a spider?
What are the digestive characteristics of spiders?
What is the structure of the circulatory system of a spider?
How does a spider breathe?
What is the structure of the excretory system of a spider?
What is the structure of the nervous system of a spider?
What is the structure of the reproductive system of a spider?
How does the cross-spider reproduce?
What is the importance of spiders?
Class Arachnids Cross-spider
Rice. Spider-cross: 1 - female, 2 - male and wheel-shaped trapping net.
Rice. Spider-cross weaves a trapping web
Class Arachnids Cross-spider
Rice. The internal structure of the Spider-cross.
1 - poisonous glands; 2 - throat; 3 - blind outgrowths of the intestine; 4 - malpighian vessels; 5 - heart; 6 - lung sac; 7 - ovary; 8 - oviduct; 9 - spider glands; 10 - pericardium; 11 - ostia in the heart.
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