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INTRODUCTIONToday; Phylum Arthropoda contain approximately 2/3 of all known species of animals. Therefore Phylum Arthropoda is the richest animal group in the world regarding to species number and also individual number. Also, insects which have a large species diversity in animal world are in this group. Class Arachnida which exists in phylum Arthropoda and has a large spectrum which includes different groups such as Spiders ,Scorpions, Uropygies, Solifugaes, Amblypygies, Opilionids, Acars, Pseudoscorpions, Palpigradies, Schzomids, Ricinuleies. Spiders can inhabit in all types of the habitats and ecosystems. Spiders have a large spreading area, from the poles to insides of the continents and from the surface of the sea to the 5000 m. elevations. However, most of the spiders live in lands, a few of spiders live in coasts or on the surface of fresh water or in it. Generally, they dwell in the gardens, on the walls, under the eaves of houses by setting up webs. Today, spiders, live in continental ecosystems are defined as effective predators of insects and arthropods.
MorphologySpiders have two parts to the body. These are prosoma and opisthosoma which are jointed with a pedicel. The first pair of members on prosoma, are cheliserae. A pair of poison glands are located on binding site of cheliserea to prosoma. The poison ducts of glands, connected to cheliserea, opens to pincers which are on the tip of cheliserea and is used as bitting needle. The poisons provide to eat preys more easily by causing paralysises. Second members are the pedipalps which are composed of six segments. Other members are the walking legs, there are 4 pairs of walking legs which are composed of seven segments. Segments from basal plate to tip of legs are coxa, trochanter, femur, patella, tibia, metetarsus, tarsus. In front of the head, generally 8 (sometimes 6) eyes arrange in 2 or 3 rows. Although opisthosoma has different sizes, it has not an important role in systematic. Folium which resembles to a hearth or a leave is situated on the dorsal. Anus is located on the back side of the opisthosoma, there are 3 pairs of spinerets just botom of it. The webs which emerge from the spinerets differs according to the species. Genital hole is located on front-middle part of the opisthosoma’s ventral. Tuber trache stigmas which are the opennings of respiratory system are situated on front-middle of spinerets.
PhenologySpiderlings, hatched from the eggs, are cared by female spider for a few days, and then leave from nest and spin their webs in certain habitats and inhabit there. This shows that spiders have ability of spining webs before maturing. Spiders are dioecious animals. The males have a pair of testises which lie down on both sides of the opisthoma like tubes. Testises open to out by a sexual hole which is located on the back epigastic furrow. Pedipalpus is the male copulatory organ. In the female reproduction system, ovaries resemble sacs which lie up from abdomen to back side. Spiders show sexual diamorphism. Generally male is smaller than female. Chemotaxis and touching organs are well-developed for mating on species those exhibit many different behaviors. They secrete chemicals called pheromone to attract the attention of opposite sex. At once time they can lay 300-3000 eggs. The eggs are carried in cocoon, sometimes connected to mother. The spiderlings stay in cocoon, until first moulting. Hatched spiderlings look like matures and a larva period is not seen. An immature spider moults 6-8 times until being mature. Spiders mature in certain periods of the year. Maturing generally begins at spring months and continues until autumn. Some species can mature during the year. Generally they mature in May and June. The life span of spiders can change for 1-2 up to 10 years. Spiders, which live long time generally inhabit in tropical regions. Spider is divided into two suborders as Orthognatha and Labidognatha. Spiders in Orthognatha have simple structures and survive in tropical and desert ecosystems.
Genital structureLabidognatha is divided into two groups regarding to genital organs having whether complex or not. Haplogyne and Entelegyne spiders are the groups of Labidognatha. However haplogynes generally have simple palps and epigyne, palps and epigyne of Entelegyne spiders get a key-lock property because of the complex structure with extra chitin. Both male and female have a genital hole lying down just at the hind of lungs in front-middle of opisthosoma. Pedipalp is the copulatory organ of male spiders. Femur, patella or tibia and pedipalps can make extensions called “Apophyse” from tip to front, which can changes in thickness and length. In spite of existing tracheas, they do not show branching out in all parts of body like insects. They spread especially in opisthosoma.
PhysiologyFeeding and digestive systemMost of the spiders are poliphage animals and their diet forms of the juices which they suck from the bodies of insects and other animals. Initial structure of the digestive system is the mouth and the following structure is a short pharynx. Pharynx opens to absorbtive stomach. There is a middle intestine which composed of saclike stuctures, cecums. Small intestine enlarges in the opisthosoma reigon where it connected to liver with a few slim ducts. Following part of the small intestine has a slim, flat and pipelike structure. It enlarges again near the end to form a sac and opens out through the anus. Intestine is wrapped with digestive glands and liver in opistoma region.
Respiratory systemRespiration is carried out with trachea and book lungs. Book lungs generally composed of two sacs. Each sac have 15-20 leavelike lamellas wrapped with slim vessels. Air is taken in from the holes opening out and by this way blood is refreshed. Altough, trachea exist in addition to book lungs, do not branche in all parts of the body as in insects. Particulary they branch into opisthosoma.
Nervous SystemA brain (a ganglion with 2 lobes) is located on head region and also a ganglion (subesephageal ganglion) group is located on breast region. Nervous cells are extended from the brain to ganglion. All above form nervous system. Although there are sense hairs on pedipalps and walking legs, main sense organs are admitted as eyes. Generally they have 8 eyes of which size and posture forms differ among species. Spiders can clearly see objects far from 10-15 cm distance of it.
Circulatory SystemThe circulatory system composed of 3 or 4 ostiumed hearts located on dorsal part of opisthosoma, arteries and veins, a series of body cavity and sinuses. The heart has a shape like a contractile tube which is composed of muscle, and covered by pericardium. The 3 or 4 pairs holes, extended from heart to the pericardium cavity, are called “ostium”. An artery extends from heart towards hind of the body, and an aorta opens out to front side. Aorta reaches to tissues and organs in prosoma by branching out. The colorless blood, which has amoeboid and cells circulates into body cavities are purified in book lungs. Purified blood comes pericardium by veins and then return to heart passing trough the ostiums.
Excretory SystemThe excretory system is composed of malpighian tubes and 2 coxal glands. Malpighian tubes are connected to small intestine. The two coxal glands open out from the binding site of basal plate to walking legs IV . Coxal glands had been lost in some species, therefore, it is hard to find the openings of the coxal glands in that species. Coxal glands are homologs of the antennal glands of fresh water lobsters. However, these glands resemble to nephridiums of the annelids, there is not any cilium in their ducts.
General ProportiesCamouflage, mocking and mimicrySpiders have other adaptations which are more effective than the adaptations against to changings in enverionmental conditions, in order to protect themselves from their enemies. These protective adaptations include the behaviors such as using camouflage colors or complexly mocking. Most of the spiders have dull body colors and do not attract the attention. However Micrommata virencans and Araniella cucurbitina clearly have green body colors, to see them in their habitats is very difficult, because they live on the leaf. When spiders felldown, they pull their legs towards body and act like dead. This behavior called catalepsy. Using this behavior in protecting from enemies is interesting because not only spiders mock, also insects mock spiders. For example, some of the fruit flies (Rhagoletis, Zonosemata) have dark marks on their wings which resemble the legs of the jumping spiders. So they look like moving spiders when they move their wings.
WinteringEighty-five percent of spiders spend winter particularly in debris of leaf, which provide an isolation from the cold. Throughout this period, legs are in a position wrapped to body and visible body surface is in a minimum level. The microhabitat under the debris protect spiders not only from high temperature changes but also from the drought. The spiders which are active in winter in the temperate zones are not resistant the cold but active in low temperatures compared with other spiders. The garden spiders are stable at 4˚C as the other spiders and die under -7˚C. The spiders, spend winter inactive, are more resistant to cold . Most of the (Araneus sp.) can live at -20˚C in unprotect habitats. It hasn’t clearly determined how can they survive in such a cold temperature. But the presence of the glycerol as antifreeze in spider hemoelenf and because of having a higher glycerol concentration in winter months compared to summer months are the clues for illuminating the matter. But also some impasses attract the attention.
AdaptationsSpiders have developed various adaptations against to unsuitable conditions such as cold temperature, moistness, flood and shortage. Today, winter ecology and resistance against to cold of spiders which are active in winters are being studied. Spiders increase their resistance against to cold by taking shelter in microhabitats and decreasing their metabolism rate.
Poisons of spidersAll spiders have poison glades on their cheliserea and inject their poisons into preys by the fangs on the tip of cheliserea. The nerotoxic poisons of spiders cause paralysis of the respiratory system. Deaths by poisons are seen on children because of respiration insufficiency. Spiders dwell in temperate zones are not very poisonous, their effects do not cause human deaths. But spiders live in tropical regions are very poisonous that they can cause serious problems for people. Spider species that have mortal effects on humans are mostly found in Araneidae, Argiopidae, Clubionoidae, Eresidae, Loxoscelidae, Lycosidae, Theriidae families. However tarantulas are giant spiders, they are less dangerous contrary to the common opinion.
POISONINGThe subtances cause death by effecting chemical and physiological structures of the body when taken in adequate amounts are called toxins or poisons and the clinic symptoms of damages that they do in the tissues are called poisoning. Effects of poisons can change depanding on their doses and taking routes. Features of the poisons such as molecular weight, binding capacity to proteins and features of the structures that they effect are important in poisoning. Poisons mainly affect the central nervous system. Related to this effect they hind the other systems in the body depanding on the features of the poisons. In acute poisonings, the sypmtoms such as decrease in irritability, hallusination and coma can be seen. In cronic poisoning, damages on nervous system such as decrease in sensing of organs can occur.
There are three routes of poisoning; 1. Orally; Food poisonings, poisonings with drugs, with chemical substances and with alcohol. 2. By respiration; Poisoning with carbondioxide and other poisonous gasses. 3. Absorbing by skin; Poisoning with the contacts of poisonous gasses, with pesticides and because of biting and stinging of snakes, scorpions, spiders and other venomous animals. It is important to know time and route of poisoning and also amount of the poison for the first aid in acute poisonings.
Spider BitesThere are large venom glands on the basal plate of cheliserea in spiders. Therefore, almost all of the 20.000 species of spiders are venomous. These glands open out from the tip segment of the cheliserea (this segment is called fang) which sink into prey and inject the poison. The musculars around the glands are important for injection. A few spider species are venomous for humans. Because, the fangs of most species which have effective poisons are too short or fragile to penetrate into human skin. But they can be effective for children and can cause deaths. Spiders in genus Phonoeutria which live in South America have the strongest neorotoxic poison ever known and they are very dangerous for humans. Spiders in genus Lactrodectus known as black widow spiders which have the poisons effective on the neuromuscular transmission form another poisonous group. Also, spiders in genus Loxoceles and in family Argyronetidae (water spiders ) have efffective poisones. Allmost all of the spider venoms are neurotoxic. These poisons effects to neurory system and related this effect , muscular rigitidies and deaths can be occur. Contary to common opinion, small spiders have stronger poisons when comprised with the poisons of big spiders. Tarantulas are not as posionous as they are known.
SymptomsImmediate pain, burning, swelling, redness and formication are the symptoms at the bite site. Double fangs marks may be seen at the site. Cramping pain and muscle rigidity in the stomach, chest and back are the symptoms in the patient. Headage, itching, sweating, dizziness, nausea and vommiting, paralysis expecially in the legs are the other symptoms. Because of the diffucult in respiration deaths can occur particullary in children. Also gangrenne is another important symptom of spider venoms.
First AidUp site of the biting area must tight with a string or a cloth to slow the circulation of the blood. The biting area must be washed with soap and water. Appling cold with ice wrapped in a cloth or a cold, wet clothes is effective to halt the pain and also acetaminophen may be given for to stop pain. It is important to apply an antibiotic cream against to infections, particularly in children. Ammoniac or permanganate, also can be used against to infections. After these measures, patient must be carried to a hospital for further treatments might be required depending on the effect of the poison.
WebsAll of spiders have the ability of producing filamentous webs those reflect the differences between species, therefore, webs are important for classification. Spiders can spin the webs between the branches of trees, leaf, into the bushes on the grasses and ground, under the stores on the walls of houses and in the cellars. Various types of spider webs resemble to the circular concave tents or convex tents, funnels, irregular and tights fishing nets are present. Spider webs are also use as a spreading vehicle . The silks those are produced by spiders are structural proteins called fibroin. Silks emerge from the spinnerets on the tip of the ophistosoma in a liquid form then became sticky fibers when they contact with air. Therefore insects immediately stick to the web when they touch it while flying.
CourtshipSpiders have developed various behaviors to communicate each other. Mechanic, chemical and visual signs are important for courting. Particularly receptors perceive the mechanic signs such as vibrations on the web are important. Sighs which are generated by web spiders by vibrating are specific for species and probably they are adequate for mating. Ground spiders also generate vibrating signs in the mating period. They deliver the vibrations through the solid objects such as soil and leaf or through the air as a sound.
SoundingAs in insects, spiders principally sound , a trumpet banging sound by using their legs and abdomen, a metal filing sound using their stidulation organs and also make sound by the vibration of abdomen and legs.
Agricultural struggleMost of the preys of the predators in agricultural ecosystem consist of insects have soft bodies such as Collembola, Diptera and Afids. There are two layers in agricultural ecosystems where the spiders are presented, surface zone of ground and vegetation zone. Different spiders groups are presented in any of the zones. Some pesticides which are used in agricultural areas cause important decreases on the spider populations. Pesticides effect not only the harmful insects but also the spiders which are the predators of these insects. Agricultural and chemical techniques must be chosen carefully and activity of the spiders in agricultural areas must be protected and developed.
Enemies of spidersSpiders have many enemies among the fishes, amphibians, reptilians, birds and particularly rodents among the vertebrates. Most of the fishes, particularly salmon trout can hunt spiders on the water surface. It is guessed that toads live on spiders. It is known that spiders are part of the nourishment list of the reptiles, but reptiles have not got much effects on spider populations. Only a few enemies of spiders are mammals, 1-2 % of the nourishment of the insectivorous such as hedgehogs and moles consist of spiders. Bats also eat spiders. But the essential enemies of spiders are themselves. Some species live on other spider species. Because of the cannibalism, there is a natural stabilization in the spider populations.
Referances
Brignoli, P. M., 1983. A Catalogue of the Araneae 1940-1981, Part I and II. Manchester University Press. Manchester. 754 p. Foelix, R. F., 1982. Biology of Spiders. Harvard University Press. Cambridge. 514 p. Nentwig, W., 1968. Non-webbuilding spiders: prey specialists or generalists. Oecologia (Berlin) 69: 571-576. Nentwig, W., 1987. Ecophysiology of spiders. Regensburg University, Institute of Zoology. Regensburg. 815 p. Tyschchenko, V. P., 1971, Identification Key to Spiders of the European USSR, Opred Faune USSR 105, Leningrad. 281 p. (in Russian).
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