Членистоногие

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Членистоногие Временный диапазон: Самый ранний кембрий ( Фортуниан ) -
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Subkingdom:	Eumetazoa
Clade:	ParaHoxozoa
Clade:	Bilateria
Clade:	Nephrozoa
(unranked):	Protostomia
Superphylum:	Ecdysozoa
(unranked):	Panarthropoda
(unranked):	Tactopoda
Phylum:	Arthropoda Gravenhorst, 1843
Subphyla, unplaced genera, and classes
show "Dinocaridida" † (paraphyletic, sometimes treated as lobopodians) Kerygmachelidae † Pambdelurion † (possible lobopodian) Mieridduryn † (possible opabiniid) Parvibellus † (possible "Siberiid Lobopodian") Opabiniidae † Radiodonta † Cucumericrus † (possible radiodont) Caryosyntrips † (possible radiodont) Bradoriida † Deuteropoda Artiopoda † Trilobita † Agnostida (possibly trilobites) † Nektaspida † Aglaspidida † Cheloniellida † Bushizheia † Erratus † Fengzhengia † Fuxianhuiida † Isoxyida † Kiisortoqia † Kylinxia † Megacheira † (possibly paraphyletic) Chelicerata Habeliida † Pycnogonida Megacheira? † Dibasterium † Offacolidae † Prosomapoda "Synziphosurina" (paraphyletic) Xiphosura Dekatriata Chasmataspidida † Houia † Winneshiekia † Eurypterida † Arachnida Phosphatocopina (possible stem mandibulate) † Mandibulata Hymenocarina † Euthycarcinoidea † Thylacocephala? † Myriapoda Symphyla Pauropoda Diplopoda Chilopoda Pancrustacea Oligostraca Ostracoda Mystacocarida Ichthyostraca Multicrustacea Cyclida † Thecostraca Tantulocarida Copepoda Malacostraca Allotriocarida Cephalocarida Branchiopoda Remipedia Hexapoda Collembola Protura Diplura Insecta Incertae sedis Aaveqaspis † Bennettarthra † Cambropachycope † Camptophyllia † Chuandianella † Goticaris † Marrellomorpha † Parioscorpio † Rhynimonstrum † Sarotrocercus † Strabopida † Wingertshellicus † Zhenghecaris †
Diversity
around 1,170,000 species.
Synonyms
Condylipoda Latreille, 1802

Arthropods ( / ˈ ɑːr θ r ə p ɒ d / ARTH -rə-pod ) беспозвоночные ​ в филоме членистоногих . Они обладают экзоскелетом с кутикулой из хитина , часто минерализованной с карбонатом кальция , телом с дифференцированными ( метамеричными ) сегментами и парными соединенными придатками . Чтобы продолжать расти, они должны пройти через стадии линьки , процесс, посредством которого они проливают свой экзоскелет , чтобы раскрыть новый. Они образуют чрезвычайно разнообразную группу до десяти миллионов видов.

Гемолимфа является аналогом крови для большинства членистоногих. Членистоногие имеют открытую систему кровообращения с полостью тела, называемой гемоцелью, через которое гемолимфа циркулирует внутренние органы . Как и их экстерьеры, внутренние органы членистоногих обычно построены из повторных сегментов. У них есть лестница, похожие на нервные системы , с парными вентральными нервными шнурами, проходящими по всем сегментам и образуют парные ганглии в каждом сегменте. Их головы образуются путем слияния различного количества сегментов, а их мозг образуется путем слияния ганглиев этих сегментов и окружения пищевода . Респираторные подбоя и экскреторные системы членистоногих варьируются в зависимости от их окружающей среды, как и от , к которому они принадлежат.

Arthropods use combinations of compound eyes and pigment-pit ocelli for vision. In most species, the ocelli can only detect the direction from which light is coming, and the compound eyes are the main source of information, but the main eyes of spiders are ocelli that can form images and, in a few cases, can swivel to track prey. Arthropods also have a wide range of chemical and mechanical sensors, mostly based on modifications of the many bristles known as setae that project through their cuticles. Similarly, their reproduction and development are varied; all terrestrial species use internal fertilization, but this is sometimes by indirect transfer of the sperm via an appendage or the ground, rather than by direct injection. Aquatic species use either internal or external fertilization. Almost all arthropods lay eggs, with many species giving birth to live young after the eggs have hatched inside the mother; but a few are genuinely viviparous, such as aphids. Arthropod hatchlings vary from miniature adults to grubs and caterpillars that lack jointed limbs and eventually undergo a total metamorphosis to produce the adult form. The level of maternal care for hatchlings varies from nonexistent to the prolonged care provided by social insects.

The evolutionary ancestry of arthropods dates back to the Cambrian period. The group is generally regarded as monophyletic, and many analyses support the placement of arthropods with cycloneuralians (or their constituent clades) in a superphylum Ecdysozoa. Overall, however, the basal relationships of animals are not yet well resolved. Likewise, the relationships between various arthropod groups are still actively debated. Today, arthropods contribute to the human food supply both directly as food, and more importantly, indirectly as pollinators of crops. Some species are known to spread severe disease to humans, livestock, and crops.

Etymology

The word arthropod comes from the Greek ἄρθρον árthron 'joint', and πούς pous (gen. ποδός podos) 'foot' or 'leg', which together mean "jointed leg", with the word "arthropodes" initially used in anatomical descriptions by Barthélemy Charles Joseph Dumortier published in 1832. The designation "Arthropoda" appears to have been first used in 1843 by the German zoologist Johann Ludwig Christian Gravenhorst (1777–1857). The origin of the name has been the subject of considerable confusion, with credit often given erroneously to Pierre André Latreille or Karl Theodor Ernst von Siebold instead, among various others.

Terrestrial arthropods are often called bugs. The term is also occasionally extended to colloquial names for freshwater or marine crustaceans (e.g., Balmain bug, Moreton Bay bug, mudbug) and used by physicians and bacteriologists for disease-causing germs (e.g., superbugs), but entomologists reserve this term for a narrow category of "true bugs", insects of the order Hemiptera.

Description

Arthropods are invertebrates with segmented bodies and jointed limbs. The exoskeleton or cuticles consists of chitin, a polymer of N-Acetylglucosamine. The cuticle of many crustaceans, beetle mites, the clades Penetini and Archaeoglenini inside the beetle subfamily Phrenapatinae, and millipedes (except for bristly millipedes) is also biomineralized with calcium carbonate. Calcification of the endosternite, an internal structure used for muscle attachments, also occur in some opiliones, and the pupal cuticle of the fly Bactrocera dorsalis contains calcium phosphate.

Diversity

Protaetia cuprea (copper chafer). Beetles are the most diverse order of arthropods.

Arthropoda is the largest animal phylum with the estimates of the number of arthropod species varying from 1,170,000 to 5 to 10 million and accounting for over 80 percent of all known living animal species. One arthropod sub-group, the insects, includes more described species than any other taxonomic class. The total number of species remains difficult to determine. This is due to the census modeling assumptions projected onto other regions in order to scale up from counts at specific locations applied to the whole world. A study in 1992 estimated that there were 500,000 species of animals and plants in Costa Rica alone, of which 365,000 were arthropods.

They are important members of marine, freshwater, land and air ecosystems and one of only two major animal groups that have adapted to life in dry environments; the other is amniotes, whose living members are reptiles, birds and mammals. Both the smallest and largest arthropods are crustaceans. The smallest belong to the class Tantulocarida, some of which are less than 100 micrometres (0.0039 in) long. The largest are species in the class Malacostraca, with the legs of the Japanese spider crab potentially spanning up to 4 metres (13 ft) and the American lobster reaching weights over 20 kg (44 lbs).

Segmentation

Head

_______________________

Thorax

_______________________

Abdomen

_______________________

Segments and tagmata of an arthropod

Structure of a biramous appendage.

The embryos of all arthropods are segmented, built from a series of repeated modules. The last common ancestor of living arthropods probably consisted of a series of undifferentiated segments, each with a pair of appendages that functioned as limbs. However, all known living and fossil arthropods have grouped segments into tagmata in which segments and their limbs are specialized in various ways.

The three-part appearance of many insect bodies and the two-part appearance of spiders is a result of this grouping. There are no external signs of segmentation in mites. Arthropods also have two body elements that are not part of this serially repeated pattern of segments, an ocular somite at the front, where the mouth and eyes originated, and a telson at the rear, behind the anus.

Originally it seems that each appendage-bearing segment had two separate pairs of appendages: an upper, unsegmented exite and a lower, segmented endopod. These would later fuse into a single pair of biramous appendages united by a basal segment (protopod or basipod), with the upper branch acting as a gill while the lower branch was used for locomotion. The appendages of most crustaceans and some extinct taxa such as trilobites have another segmented branch known as exopods, but whether these structures have a single origin remain controversial. In some segments of all known arthropods the appendages have been modified, for example to form gills, mouth-parts, antennae for collecting information, or claws for grasping; arthropods are "like Swiss Army knives, each equipped with a unique set of specialized tools." In many arthropods, appendages have vanished from some regions of the body; it is particularly common for abdominal appendages to have disappeared or be highly modified.

Alignment of anterior body segments and appendages across various arthropod taxa, based on the observations until the mid 2010s. Head regions in black.

The most conspicuous specialization of segments is in the head. The four major groups of arthropods – Chelicerata (sea spiders, horseshoe crabs and arachnids), Myriapoda (symphylans, pauropods, millipedes and centipedes), Pancrustacea (oligostracans, copepods, malacostracans, branchiopods, hexapods, etc.), and the extinct Trilobita – have heads formed of various combinations of segments, with appendages that are missing or specialized in different ways. Despite myriapods and hexapods both having similar head combinations, hexapods are deeply nested within crustacea while myriapods are not, so these traits are believed to have evolved separately. In addition, some extinct arthropods, such as Marrella, belong to none of these groups, as their heads are formed by their own particular combinations of segments and specialized appendages.

Working out the evolutionary stages by which all these different combinations could have appeared is so difficult that it has long been known as "The arthropod head problem". In 1960, R. E. Snodgrass even hoped it would not be solved, as he found trying to work out solutions to be fun.

Exoskeleton

Main article: Arthropod exoskeleton

Illustration of an idealized arthropod exoskeleton.

Arthropod exoskeletons are made of cuticle, a non-cellular material secreted by the epidermis. Their cuticles vary in the details of their structure, but generally consist of three main layers: the epicuticle, a thin outer waxy coat that moisture-proofs the other layers and gives them some protection; the exocuticle, which consists of chitin and chemically hardened proteins; and the endocuticle, which consists of chitin and unhardened proteins. The exocuticle and endocuticle together are known as the procuticle. Each body segment and limb section is encased in hardened cuticle. The joints between body segments and between limb sections are covered by flexible cuticle.

The exoskeletons of most aquatic crustaceans are biomineralized with calcium carbonate extracted from the water. Some terrestrial crustaceans have developed means of storing the mineral, since on land they cannot rely on a steady supply of dissolved calcium carbonate. Biomineralization generally affects the exocuticle and the outer part of the endocuticle. Two recent hypotheses about the evolution of biomineralization in arthropods and other groups of animals propose that it provides tougher defensive armor, and that it allows animals to grow larger and stronger by providing more rigid skeletons; and in either case a mineral-organic composite exoskeleton is cheaper to build than an all-organic one of comparable strength.

The cuticle may have setae (bristles) growing from special cells in the epidermis. Setae are as varied in form and function as appendages. For example, they are often used as sensors to detect air or water currents, or contact with objects; aquatic arthropods use feather-like setae to increase the surface area of swimming appendages and to filter food particles out of water; aquatic insects, which are air-breathers, use thick felt-like coats of setae to trap air, extending the time they can spend under water; heavy, rigid setae serve as defensive spines.

Although all arthropods use muscles attached to the inside of the exoskeleton to flex their limbs, some still use hydraulic pressure to extend them, a system inherited from their pre-arthropod ancestors; for example, all spiders extend their legs hydraulically and can generate pressures up to eight times their resting level.

Moulting

Main article: Ecdysis

Cicada climbing out of its exuviae while attached to tree

The exoskeleton cannot stretch and thus restricts growth. Arthropods, therefore, replace their exoskeletons by undergoing ecdysis (moulting), or shedding the old exoskeleton, the exuviae, after growing a new one that is not yet hardened. Moulting cycles run nearly continuously until an arthropod reaches full size. The developmental stages between each moult (ecdysis) until sexual maturity is reached is called an instar. Differences between instars can often be seen in altered body proportions, colors, patterns, changes in the number of body segments or head width. After moulting, i.e. shedding their exoskeleton, the juvenile arthropods continue in their life cycle until they either pupate or moult again.

In the initial phase of moulting, the animal stops feeding and its epidermis releases moulting fluid, a mixture of enzymes that digests the endocuticle and thus detaches the old cuticle. This phase begins when the epidermis has secreted a new epicuticle to protect it from the enzymes, and the epidermis secretes the new exocuticle while the old cuticle is detaching. When this stage is complete, the animal makes its body swell by taking in a large quantity of water or air, and this makes the old cuticle split along predefined weaknesses where the old exocuticle was thinnest. It commonly takes several minutes for the animal to struggle out of the old cuticle. At this point, the new one is wrinkled and so soft that the animal cannot support itself and finds it very difficult to move, and the new endocuticle has not yet formed. The animal continues to pump itself up to stretch the new cuticle as much as possible, then hardens the new exocuticle and eliminates the excess air or water. By the end of this phase, the new endocuticle has formed. Many arthropods then eat the discarded cuticle to reclaim its materials.

Because arthropods are unprotected and nearly immobilized until the new cuticle has hardened, they are in danger both of being trapped in the old cuticle and of being attacked by predators. Moulting may be responsible for 80 to 90% of all arthropod deaths.

Internal organs

  = heart

  = gut

  = brain / ganglia

 O = eye

Basic arthropod body structure

Arthropod bodies are also segmented internally, and the nervous, muscular, circulatory, and excretory systems have repeated components. Arthropods come from a lineage of animals that have a coelom, a membrane-lined cavity between the gut and the body wall that accommodates the internal organs. The strong, segmented limbs of arthropods eliminate the need for one of the coelom's main ancestral functions, as a hydrostatic skeleton, which muscles compress in order to change the animal's shape and thus enable it to move. Hence the coelom of the arthropod is reduced to small areas around the reproductive and excretory systems. Its place is largely taken by a hemocoel, a cavity that runs most of the length of the body and through which blood flows.

Respiration and circulation

See also: Hemolymph and hemocyte

Respiration and circulation in a myodocopid ostracod. Simplified transverse section through anterior body and carapace, showing gaseous diffusion through the inner lamella of the carapace (yellow arrows)

Arthropods have open circulatory systems. Most have a few short, open-ended arteries. In chelicerates and crustaceans, the blood carries oxygen to the tissues, while hexapods use a separate system of tracheae. Many crustaceans and a few chelicerates and tracheates use respiratory pigments to assist oxygen transport. The most common respiratory pigment in arthropods is copper-based hemocyanin; this is used by many crustaceans and a few centipedes. A few crustaceans and insects use iron-based hemoglobin, the respiratory pigment used by vertebrates. As with other invertebrates, the respiratory pigments of those arthropods that have them are generally dissolved in the blood and rarely enclosed in corpuscles as they are in vertebrates.

The heart is a muscular tube that runs just under the back and for most of the length of the hemocoel. It contracts in ripples that run from rear to front, pushing blood forwards. Sections not being squeezed by the heart muscle are expanded either by elastic ligaments or by small muscles, in either case connecting the heart to the body wall. Along the heart run a series of paired ostia, non-return valves that allow blood to enter the heart but prevent it from leaving before it reaches the front.

Arthropods have a wide variety of respiratory systems. Small species often do not have any, since their high ratio of surface area to volume enables simple diffusion through the body surface to supply enough oxygen. Crustacea usually have gills that are modified appendages. Many arachnids have book lungs. Tracheae, systems of branching tunnels that run from the openings in the body walls, deliver oxygen directly to individual cells in many insects, myriapods and arachnids.

Nervous system

Central nervous system of a nectiopod remipede, showing the presence of both deutocerebrum (dc) and ventral nerve cord (vnc) organized by segmented ganglia.

Living arthropods have paired main nerve cords running along their bodies below the gut, and in each segment the cords form a pair of ganglia from which sensory and motor nerves run to other parts of the segment. Although the pairs of ganglia in each segment often appear physically fused, they are connected by commissures (relatively large bundles of nerves), which give arthropod nervous systems a characteristic ladder-like appearance. The brain is in the head, encircling and mainly above the esophagus. It consists of the fused ganglia of the acron and one or two of the foremost segments that form the head – a total of three pairs of ganglia in most arthropods, but only two in chelicerates, which do not have antennae or the ganglion connected to them. The ganglia of other head segments are often close to the brain and function as part of it. In insects these other head ganglia combine into a pair of subesophageal ganglia, under and behind the esophagus. Spiders take this process a step further, as all the segmental ganglia are incorporated into the subesophageal ganglia, which occupy most of the space in the cephalothorax (front "super-segment").

Excretory system

There are two different types of arthropod excretory systems. In aquatic arthropods, the end-product of biochemical reactions that metabolise nitrogen is ammonia, which is so toxic that it needs to be diluted as much as possible with water. The ammonia is then eliminated via any permeable membrane, mainly through the gills. All crustaceans use this system, and its high consumption of water may be responsible for the relative lack of success of crustaceans as land animals. Various groups of terrestrial arthropods have independently developed a different system: the end-product of nitrogen metabolism is uric acid, which can be excreted as dry material; the Malpighian tubule system filters the uric acid and other nitrogenous waste out of the blood in the hemocoel, and dumps these materials into the hindgut, from which they are expelled as feces. Most aquatic arthropods and some terrestrial ones also have organs called nephridia ("little kidneys"), which extract other wastes for excretion as urine.

Senses

Long bristles (setae) of a Tliltocatl albopilosus tarantula

The stiff cuticles of arthropods would block out information about the outside world, except that they are penetrated by many sensors or connections from sensors to the nervous system. In fact, arthropods have modified their cuticles into elaborate arrays of sensors. Various touch sensors, mostly setae, respond to different levels of force, from strong contact to very weak air currents. Chemical sensors provide equivalents of taste and smell, often by means of setae. Pressure sensors often take the form of membranes that function as eardrums, but are connected directly to nerves rather than to auditory ossicles. The antennae of most hexapods include sensor packages that monitor humidity, moisture and temperature.

Most arthropods lack balance and acceleration sensors, and rely on their eyes to tell them which way is up. The self-righting behavior of cockroaches is triggered when pressure sensors on the underside of the feet report no pressure. However, many malacostracan crustaceans have statocysts, which provide the same sort of information as the balance and motion sensors of the vertebrate inner ear.

The proprioceptors of arthropods, sensors that report the force exerted by muscles and the degree of bending in the body and joints, are well understood. However, little is known about what other internal sensors arthropods may have.

Optical

Main article: Arthropod eye

Arthropod eyes

Head of a wasp with three ocelli (center), and compound eyes at the left and right

Most arthropods have sophisticated visual systems that include one or more usually both of compound eyes and pigment-cup ocelli ("little eyes"). In most cases ocelli are only capable of detecting the direction from which light is coming, using the shadow cast by the walls of the cup. However, the main eyes of spiders are pigment-cup ocelli that are capable of forming images, and those of jumping spiders can rotate to track prey.

Compound eyes consist of fifteen to several thousand independent ommatidia, columns that are usually hexagonal in cross section. Each ommatidium is an independent sensor, with its own light-sensitive cells and often with its own lens and cornea. Compound eyes have a wide field of view, and can detect fast movement and, in some cases, the polarization of light. On the other hand, the relatively large size of ommatidia makes the images rather coarse, and compound eyes are shorter-sighted than those of birds and mammals – although this is not a severe disadvantage, as objects and events within 20 cm (8 in) are most important to most arthropods. Several arthropods have color vision, and that of some insects has been studied in detail; for example, the ommatidia of bees contain receptors for both green and ultra-violet.

Olfaction

Further information: Insect olfaction

Reproduction and development

Aphid giving birth to live young from an unfertilized egg

Harvestmen mating

A few arthropods, such as barnacles, are hermaphroditic, that is, each can have the organs of both sexes. However, individuals of most species remain of one sex their entire lives. A few species of insects and crustaceans can reproduce by parthenogenesis, especially if conditions favor a "population explosion". However, most arthropods rely on sexual reproduction, and parthenogenetic species often revert to sexual reproduction when conditions become less favorable. The ability to undergo meiosis is widespread among arthropods including both those that reproduce sexually and those that reproduce parthenogenetically. Although meiosis is a major characteristic of arthropods, understanding of its fundamental adaptive benefit has long been regarded as an unresolved problem, that appears to have remained unsettled.

Aquatic arthropods may breed by external fertilization, as for example horseshoe crabs do, or by internal fertilization, where the ova remain in the female's body and the sperm must somehow be inserted. All known terrestrial arthropods use internal fertilization. Opiliones (harvestmen), millipedes, and some crustaceans use modified appendages such as gonopods or penises to transfer the sperm directly to the female. However, most male terrestrial arthropods produce spermatophores, waterproof packets of sperm, which the females take into their bodies. A few such species rely on females to find spermatophores that have already been deposited on the ground, but in most cases males only deposit spermatophores when complex courtship rituals look likely to be successful.

The nauplius larva of a penaeid shrimp

Most arthropods lay eggs, but scorpions are ovoviviparous: they produce live young after the eggs have hatched inside the mother, and are noted for prolonged maternal care. Newly born arthropods have diverse forms, and insects alone cover the range of extremes. Some hatch as apparently miniature adults (direct development), and in some cases, such as silverfish, the hatchlings do not feed and may be helpless until after their first moult. Many insects hatch as grubs or caterpillars, which do not have segmented limbs or hardened cuticles, and metamorphose into adult forms by entering an inactive phase in which the larval tissues are broken down and re-used to build the adult body. Dragonfly larvae have the typical cuticles and jointed limbs of arthropods but are flightless water-breathers with extendable jaws. Crustaceans commonly hatch as tiny nauplius larvae that have only three segments and pairs of appendages.

Evolutionary history

See also: Phylogeny of insects

Last common ancestor

Based on the distribution of shared plesiomorphic features in extant and fossil taxa, the last common ancestor of all arthropods is inferred to have been as a modular organism with each module covered by its own sclerite (armor plate) and bearing a pair of biramous limbs. However, whether the ancestral limb was uniramous or biramous is far from a settled debate. This Ur-arthropod had a ventral mouth, pre-oral antennae and dorsal eyes at the front of the body. It was assumed to have been a non-discriminatory sediment feeder, processing whatever sediment came its way for food, but fossil findings hint that the last common ancestor of both arthropods and Priapulida shared the same specialized mouth apparatus; a circular mouth with rings of teeth used for capturing animal prey.

Fossil record

Marrella, one of the puzzling arthropods from the Burgess Shale

It has been proposed that the Ediacaran animals Parvancorina and Spriggina, from around 555 million years ago, were arthropods, but later study shows that their affinities of being origin of arthropods are not reliable. Small arthropods with bivalve-like shells have been found in Early Cambrian fossil beds dating 541 to 539 million years ago in China and Australia. The earliest Cambrian trilobite fossils are about 520 million years old, but the class was already quite diverse and worldwide, suggesting that they had been around for quite some time. In the Maotianshan shales, which date back to 518 million years ago, arthropods such as Kylinxia and Erratus have been found that seem to represent transitional fossils between stem (e.g. Radiodonta such as Anomalocaris) and true arthropods. Re-examination in the 1970s of the Burgess Shale fossils from about 505 million years ago identified many arthropods, some of which could not be assigned to any of the well-known groups, and thus intensified the debate about the Cambrian explosion. A fossil of Marrella from the Burgess Shale has provided the earliest clear evidence of moulting.

Kylinxia may be a key transitional fossil between stem-arthropods and true arthropods.

Yicaris is one of the earliest crustaceans that have been discovered.

The earliest fossil of likely pancrustacean larvae date from about 514 million years ago in the Cambrian, followed by unique taxa like Yicaris and Wujicaris. The purported pancrustacean/crustacean affinity of some cambrian arthropods (e.g. Phosphatocopina, Bradoriida and Hymenocarine taxa like waptiids) were disputed by subsequent studies, as they might branch before the mandibulate crown-group. Within the pancrustacean crown-group, only Malacostraca, Branchiopoda and Pentastomida have Cambrian fossil records. Crustacean fossils are common from the Ordovician period onwards. They have remained almost entirely aquatic, possibly because they never developed excretory systems that conserve water.

Arthropods provide the earliest identifiable fossils of land animals, from about 419 million years ago in the Late Silurian, and terrestrial tracks from about 450 million years ago appear to have been made by arthropods. Arthropods possessed attributes that were easy coopted for life on land; their existing jointed exoskeletons provided protection against desiccation, support against gravity and a means of locomotion that was not dependent on water. Around the same time the aquatic, scorpion-like eurypterids became the largest ever arthropods, some as long as 2.5 m (8 ft 2 in).

The oldest known arachnid is the trigonotarbid Palaeotarbus jerami, from about 420 million years ago in the Silurian period. Attercopus fimbriunguis, from 386 million years ago in the Devonian period, bears the earliest known silk-producing spigots, but its lack of spinnerets means it was not one of the true spiders, which first appear in the Late Carboniferous over 299 million years ago. The Jurassic and Cretaceous periods provide a large number of fossil spiders, including representatives of many modern families. The oldest known scorpion is Dolichophonus, dated back to 436 million years ago. Lots of Silurian and Devonian scorpions were previously thought to be gill-breathing, hence the idea that scorpions were primitively aquatic and evolved air-breathing book lungs later on. However subsequent studies reveal most of them lacking reliable evidence for an aquatic lifestyle, while exceptional aquatic taxa (e.g. Waeringoscorpio) most likely derived from terrestrial scorpion ancestors.

The oldest fossil record of hexapod is obscure, as most of the candidates are poorly preserved and their hexapod affinities had been disputed. An iconic example is the Devonian Rhyniognatha hirsti, dated at 396 to 407 million years ago, its mandibles are thought to be a type found only in winged insects, which suggests that the earliest insects appeared in the Silurian period. However later study shows that Rhyniognatha most likely represent a myriapod, not even a hexapod. The unequivocal oldest known hexapod and insect is the springtail Rhyniella, from about 410 million years ago in the Devonian period, and the palaeodictyopteran Delitzschala bitterfeldensis, from about 325 million years ago in the Carboniferous period, respectively. The Mazon Creek lagerstätten from the Late Carboniferous, about 300 million years ago, include about 200 species, some gigantic by modern standards, and indicate that insects had occupied their main modern ecological niches as herbivores, detritivores and insectivores. Social termites and ants first appear in the Early Cretaceous, and advanced social bees have been found in Late Cretaceous rocks but did not become abundant until the Middle Cenozoic.

Evolutionary relationships to other animal phyla

The velvet worm (Onychophora) is closely related to arthropods

From 1952 to 1977, zoologist Sidnie Manton and others argued that arthropods are polyphyletic, in other words, that they do not share a common ancestor that was itself an arthropod. Instead, they proposed that three separate groups of "arthropods" evolved separately from common worm-like ancestors: the chelicerates, including spiders and scorpions; the crustaceans; and the uniramia, consisting of onychophorans, myriapods and hexapods. These arguments usually bypassed trilobites, as the evolutionary relationships of this class were unclear. Proponents of polyphyly argued the following: that the similarities between these groups are the results of convergent evolution, as natural consequences of having rigid, segmented exoskeletons; that the three groups use different chemical means of hardening the cuticle; that there were significant differences in the construction of their compound eyes; that it is hard to see how such different configurations of segments and appendages in the head could have evolved from the same ancestor; and that crustaceans have biramous limbs with separate gill and leg branches, while the other two groups have uniramous limbs in which the single branch serves as a leg.

	onychophorans   includes Aysheaia and Peripatus       armored lobopods   includes Hallucigenia and Microdictyon   dinocarids (s.l.)     anomalocarid-   includes modern tardigrades as well as extinct animals like Kerygmachela and Opabinia like taxa (s.l.)   anomalocarids (s.s.)   Anomalocaris   arthropods   includes living groups and extinct forms such as trilobites

Simplified summary of Budd's (1996) "broad-scale" cladogram

Further analysis and discoveries in the 1990s reversed this view, and led to acceptance that arthropods are monophyletic, in other words they are inferred to share a common ancestor that was itself an arthropod. For example, Graham Budd's analyses of Kerygmachela in 1993 and of Opabinia in 1996 convinced him that these animals were similar to onychophorans and to various Early Cambrian "lobopods", and he presented an "evolutionary family tree" that showed these as "aunts" and "cousins" of all arthropods. These changes made the scope of the term "arthropod" unclear, and Claus Nielsen proposed that the wider group should be labelled "Panarthropoda" ("all the arthropods") while the animals with jointed limbs and hardened cuticles should be called "Euarthropoda" ("true arthropods").

A contrary view was presented in 2003, when Jan Bergström and Hou Xian-guang argued that, if arthropods were a "sister-group" to any of the anomalocarids, they must have lost and then re-evolved features that were well-developed in the anomalocarids. The earliest known arthropods ate mud in order to extract food particles from it, and possessed variable numbers of segments with unspecialized appendages that functioned as both gills and legs. Anomalocarids were, by the standards of the time, huge and sophisticated predators with specialized mouths and grasping appendages, fixed numbers of segments some of which were specialized, tail fins, and gills that were very different from those of arthropods. In 2006, they suggested that arthropods were more closely related to lobopods and tardigrades than to anomalocarids. In 2014, it was found that tardigrades were more closely related to arthropods than velvet worms.

Protostomes	Chaetognatha Spiralia (annelids, molluscs, brachiopods, etc.) Ecdysozoa Nematoida (nematodes and close relatives) Scalidophora (priapulids and Kinorhyncha, and Loricifera) Panarthropoda Onychophorans Tactopoda Tardigrades Euarthropoda Chelicerates Mandibulata †Euthycarcinoids Myriapods Pancrustacea Crustaceans Hexapods
Relationships of Ecdysozoa to each other and to annelids, etc., including euthycarcinoids

Higher up the "family tree", the Annelida have traditionally been considered the closest relatives of the Panarthropoda, since both groups have segmented bodies, and the combination of these groups was labelled Articulata. There had been competing proposals that arthropods were closely related to other groups such as nematodes, priapulids and tardigrades, but these remained minority views because it was difficult to specify in detail the relationships between these groups.

In the 1990s, molecular phylogenetic analyses of DNA sequences produced a coherent scheme showing arthropods as members of a superphylum labelled Ecdysozoa ("animals that moult"), which contained nematodes, priapulids and tardigrades but excluded annelids. This was backed up by studies of the anatomy and development of these animals, which showed that many of the features that supported the Articulata hypothesis showed significant differences between annelids and the earliest Panarthropods in their details, and some were hardly present at all in arthropods. This hypothesis groups annelids with molluscs and brachiopods in another superphylum, Lophotrochozoa.

If the Ecdysozoa hypothesis is correct, then segmentation of arthropods and annelids either has evolved convergently or has been inherited from a much older ancestor and subsequently lost in several other lineages, such as the non-arthropod members of the Ecdysozoa.

Evolution of fossil arthropods

Further information: Deuteropoda

Arthropod fossil phylogeny

Членистоногие giant lobopodians † gilled lobopodians † Radiodonta † Второпода Chelicerata Мегачера † Artiopoda † В Иисусе † Жемчужина

Суммировала кладограмму взаимосвязей между вымершими группами членистоногих. Для получения дополнительной информации см. Deuteropoda .

Aside from the four major living groups (crustaceans, chelicerates, myriapods and hexapods), a number of fossil forms, mostly from the early Cambrian period, are difficult to place taxonomically, either from lack of obvious affinity to any of the main groups or from clear affinity to several of them. Marrella was the first one to be recognized as significantly different from the well-known groups.

Современные интерпретации базальной, вымершей группы ствола членистоногих признали следующие группы, от большинства базальных до большинства корон.

• « Гигантские » или «сибирид лобоподиан» , такие как Цзяньшаноподия , Сибир и Мегадиктион , являются наиболее базальными в чёрподе общей группы.
• «Gilled Lobopodians » , такие как Kerygmachela , Pampdelurion и Opabinia , являются вторым наиболее базальным сортом.
• Radiodonta , которая , традиционно известная как аномалокаридиды, занимает третью позицию и считается монофилетическим .
• Возможная сборка «верхней группы ствола» более неопределенной позиции но содержится в Deuteropoda : Fuxianhuiida включая , Megacheira и множественные «двустворчатые формы», изоксида и гименокарину .

Deuteropoda -недавно созданная клада , объединяющая черпотовые членистоногих корон (живая) с этими возможными таксонами «верхняя группа» ствола. Клада определяется важными изменениями в структуре области головы, такими как появление дифференцированной пары деутоцеребральных придаток, которая исключает больше базальных таксонов, таких как радиодонты и «жареные лобоподианцы».

Споры остаются в отношении позиций различных вымерших групповых групп членистоногих. Некоторые исследования восстанавливают мегачеру, как тесно связаны с хелисеры, в то время как другие восстанавливают их как за пределами группы, содержащей хелицерат и мандибулата в качестве эуартроподов стволовой группы. Размещение Artiopoda ( которая содержит вымершие трилобиты и аналогичные формы) также является частым предметом спора. Основные гипотезы позиционируют их в кладке арахноморфы с хелицератами. Однако одной из более новых гипотез является то, что Chelicerae возникли из той же пары придаток, которые превратились в антенны у предков Мандибулаты , которые будут помещать трилобиты, которые имели антенны, ближе к Мандибулате, чем хелицерата, в клад -антенналата . группы . Предполагается, что в некоторых недавних исследованиях Fuxianhuiids, как правило, предполагают, что являются членистоногими стволовой , Было продемонстрировано, что Hymenocarina группа двустворенных членистоногих, ранее считавшейся членами группы STEM-группы, была продемонстрирована мандибулированием на основе присутствия мандибов.

• Radiodonts, Opabiniids, Gilled Lobopodians и более традиционные лобоподианцы-все это примеры базальных линий членистоногих стволовых групп от кембрии
• 
  Anomalocaris
  ( Radiodonta )
• 
  Опабиния
  ( Opabiniidae )
• 
  Керигмачела
  ( Kerygmachelidae )
• 
  Факты
  ( Luolishaniidae )

• Marellomorphs, Megacherians, Funxianhuiids и фосфатокопины - некоторые примеры кембрийских членистоногих, классификация которых остается трудной
• 
  Marrella
  ( Marrellomorpha )
• 
  Следуйте
  ( Мегачера )
• 
  Fuxianhuia
  ( Fuxianhuida )
• 
  Дабашанелла
  ( Фосфатокопина )

• Другие примеры теперь вымерших групп членистоногих включают
• 
  Акутромус
  ( Eurypterida )
• 
  ношение Апанкуры
  ( Euthycarcinoidea )
• 
  Тримерус
  ( Артиопода )
• 
  CONCAVICARIS
  ( Тилакоцефала )

Эволюция и классификация живых членистоногие

См. Также: Список заказов членистоногих

Phylum Chrothonicoda, как правило, подразделяется на четыре субфилы , из которых один вымер :

1. Артиоподы являются вымершей группой бывших многочисленных морских животных , которые исчезли в рамках пермского и триасного вымирания , хотя до этого удара в упадке были в упадке, что было сокращено до одного порядка в позднем девонском вымирании . Они содержат группы, такие как трилобиты .
2. Хелицераты составляют морские морские пауки и подковообразные крабы , а также наземные арахниды, такие как клещи , уборщики , пауки , скорпионы и связанные с ними организмы, характеризуемые наличием Chelicerae , придатками чуть выше/перед ртами . Chelicerae появляются в скорпионах и подковообразных крабах как крошечные когти , которые они используют в кормлении, но у пауков развивались как клыки , которые вводят яд .
3. Множество мириподов включают Millipedes , Mentipedes , Pauropods и Symphylans , характеризующие многочисленные сегменты тела , каждая из которых с одной или двумя парами ног (или в некоторых случаях без ног). Все члены исключительно на земле.
4. Pancrustaceans включают остракоды , саралы , кобородообразные , малакостраканы , цефалокариданы , ветвиные , переоборудованные и гексаподы . Большинство групп в первую очередь являются водными (двумя заметными исключениями являются леса и гексапод, которые являются чисто наземными ) и характеризуются наличием бириамных придатков. Наиболее распространенной группой пансустакейцев являются наземные гексапод, которые включают насекомых , диплораны , весенние хвосты и протранцы , с шестью грудными ногами.

Филогения . основных существующих членисторонних групп была областью, представляющей значительный интерес и спор Недавние исследования убедительно свидетельствуют о том, что ракообразные, как это традиционно определено, является парафилетическим , с гексаподой, развивающимися внутри него, Так что ракообразные и гексапода образуют кладу, Pancrustacea . Положение мириаподы , челицераты и пансустачеи остается неясной по состоянию на апрель 2012 года Полем В некоторых исследованиях мириапода сгруппирована с Chelicerata (образуя мириохелата ); В других исследованиях мириапода сгруппирована с Pancrustacea (формирование Mandibulata ), или Myriapoda может быть сестрой Chelicerata Plus Pancrustacea.

Следующая кладограмма показывает внутренние отношения между всеми живыми классами членистоногих с конца 2010 -х годов, а также предполагаемое время для некоторых клад:

Членистоногие	Chelicerata Пикногонида Просомапода Xiphosura Арахнид Жемчужина Мириапода Чилопода Преследовать Эдафопода Симфила Павел есть Diplopoda PANCRUSTACEA Олигострака Остракода Мистакокарида IchthyoStraca Altocrustacea Многоцветая Hexanauplia МОПЕПОДА Тантулокарида Thecostraca Малакостра Аллотриокарида Цефалокарида Аталасокарида Branchiopoda Лабиокарида Remipedia Гексапода Эллиплура Коллембола Защита Cercophora Диплора Инсекта 440 мю 470 мю 493 Mya	Ракообразные Эндогнаты

Субфила	Классы	Члены	Пример видов
Chelicerata	Пикногонида Xiphosura Арахнид	Морские пауки Подковообразные крабы Урожайности , солифуги , клещи , скорпионы , пауки , клещи и т. Д.	Platycryptus undatus ( Arachnida , Araneae )
Мириапода	Симфила Павел есть Diplopoda Чилопода	псевдоцеттипед Гексамероцератаны , тетрамероцератаны Залив за щели , таблетки, мельницы , залив с плоскими списками и т. Д. Scutigeromorphs , Lithobiomorphs , Scolopendromorphs и т. Д.	ArchispiroStreptus Gigas ( Diplopoda , Spirostreptida )
Ракообразные	Остракода Мистакокарида Пентастомида Ветви Thecostraca МОПЕПОДА Малакостра Цефалокарида Branchiopoda Remipedia	Семена креветки Мистакокариданы Языковые черви рыбные вши Сарнаки и т. д. Каланоиды , циклопоиды , мизофриоиды , сифоностоматоиды и т. Д. Креветки богомола , скелетные креветки , вудличе , креветки , крабы , омары , криль и т. Д. Подкова креветки фея , креветки головастика , водолаза , креветки из моллюсков переоборудовано	Ocypode Ceratophthalma ( Malaconkey , Decapeda )
Гексапода	Инсекта Энтогната	насекомые весенние хвосты и т. д.	Сатурния Павония ( Insecta , Lepidoptera )

Взаимодействие с людьми

Основная статья: членистоногие в культуре

Смотрите также: насекомые как еда

Насекомые и скорпионы в продаже в продовольственном киоске в Бангкоке , Таиланд

Ракообразные, такие как крабы , лобстеры , раки , креветки и креветки , давно являются частью человеческой кухни и в настоящее время выводятся в коммерческих целях. Насекомые и их личинки, по крайней мере, такие же питательные, как мясо, и их едят как сырые, так и приготовлены во многих культурах, хотя и не большинство европейских, индуистских и исламских культур. Приготовленные тарантулы считаются деликатесом в Камбодже , и индейцами Пиароа из Южной Венесуэлы , после того, как очень раздражительные волосы - главная система защиты паука - удаляются. Люди также непреднамеренно едят членистоногие в других продуктах, А правила безопасности пищевых продуктов устанавливают приемлемые уровни загрязнения для различных видов пищевых материалов. Преднамеренное выращивание членистоногих и других мелких животных для еды человека, называемое Миниливестоком , теперь появляется в животноводстве как экологически здравая концепция. Коммерческое размножение бабочек обеспечивает Lepidoptera Stock для консерваторий -бабочек , образовательных экспонатов, школ, исследовательских учреждений и культурных мероприятий.

Тем не менее, наибольшим вкладом членистоногих в поставки продуктов питания человека является опыление : исследование 2008 года изучало 100 культур, которые ФАО перечисляет как выращенные для пищевых продуктов, и, по оценкам, экономическая стоимость опыления как 153 миллиарда евро, или 9,5 процента от стоимости мирового сельского хозяйства. Производство, используемое для еды человека в 2005 году. Помимо опыления, пчелы производят мед , который является основой быстро растущей промышленности и международной торговли.

красная краситель Кохинеальная , произведенная из центральной американской виды насекомых, была экономически важна для ацтеков и майя . В то время как регион находился под контролем испанского языка , он стал , вторым наиболее хлебительным экспортом Мексики и теперь восстанавливает часть земли, которую он потерял для синтетических конкурентов. Shellac , смола, секретируемая видом насекомых, уроженца в Южной Азии, исторически использовалась в больших количествах для многих применений, в которых она в основном заменялась синтетическими смолами, но все еще используется в деревообработке и в качестве пищевой добавки . Кровь крабов подковообразных содержит агент свертывания, лизат амебоцитов Limulus , который в настоящее время используется для проверки того, что антибиотики и машины для почек свободны от опасных бактерий , а также для обнаружения спинного менингита и некоторых раковых заболеваний . Судебная энтомология использует доказательства, предоставленные членистоногими для установления времени, а иногда и места смерти человека, а в некоторых случаях причина. Недавно насекомые также привлекли внимание как потенциальные источники лекарств и других лекарственных веществ.

Относительная простота плана тела членистоногих, позволяющая им двигаться на различных поверхностях как на суше, так и в воде, сделала их полезными в качестве моделей для робототехники . Избыточность, предоставленная сегментами, позволяет членистоногим и биомиметическим роботам перемещаться нормально даже при поврежденных или потерянных придатках.

Болезни, передаваемые насекомыми

Болезнь	Насекомое	Дела в год	Смерть в год
Малярия	Anopheles Mosquito	267 м	От 1 до 2 м
Лихорадка денге	Aedes Mosquito	?	?
Желтая лихорадка	Aedes Mosquito	4,432	1,177
Филариаз	Culex Mosquito	250 м	неизвестный

Хотя членистоногие являются наиболее многочисленным филомом на Земле, а тысячи видов членистоногих ядовиты, они наносят относительно мало серьезных укусов и укусов на людей. Гораздо более серьезные влияние на людей заболеваний, таких как малярия, несущая кровеносники насекомых. Другие кровеносники насекомые заражают скот болезнями, которые убивают многих животных и значительно снижают полезность других. Клещи могут вызвать паралич клещей и несколько паразитовых заболеваний у людей. Некоторые из близкородственных клещей также заражают людей, вызывая интенсивный зуд, и другие вызывают аллергические заболевания, включая сеную лихорадку , астму и экзему .

Многие виды членистоногих, в основном насекомых, но также и клещи, являются сельскохозяйственными и лесными вредителями. Mite Депутатор Varroa стал самой большой проблемой, с которой сталкиваются пчеловоды по всему миру. Усилия по борьбе с вредителями членистоногих путем крупномасштабного использования пестицидов вызвали долгосрочные последствия на здоровье человека и биоразнообразие . Увеличение устойчивости членистоногих пестицидов привело к разработке интегрированного лечения вредителей с использованием широкого спектра мер, включая биологический контроль . Хищные клещи могут быть полезны для контроля некоторых вредителей клещей.

Смотрите также

• Дорсальная доля
• Беспозвоночная палеонтология
• Минибаз

Ссылки

Библиография

• Гулд, С.Дж. (1990). Прекрасная жизнь: сланец Берджесса и природа истории . Радиус Хатчинсона. Bibcode : 1989wlbs.book ..... g . ISBN  978-0-09-174271-3 .
• Рупперт, EE; Р.С. Фокс; Rd Barnes (2004). Зоология беспозвоночных (7 -е изд.). Брукс/Коул . ISBN  978-0-03-025982-1 .

Внешние ссылки

• «Членистоногие» в энциклопедии жизни
• Глава ядовитых членистоногие в Соединенных Штатах Агентства по охране окружающей среды и Университета Флориды / Институт продовольственных и сельскохозяйственных наук Национальное руководство по обучению аппликаторам общественного здравоохранения
• Членистоногие - формы жизни насекомых с членистоногими