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Arthropod

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Arthropoda
Temporal range: 538.8 –0 
Ma
Earliest Cambrian (Fortunian)–Recent
AnomalocarisAtlantic horseshoe crabPenaeus monodonIsoxysAraneus diadematusChelonibia testudinariaLeanchoiliaScolopendra cataractaDicyrtominaElrathiaJuliformiaCarniolan honey beeArthropoda collage.png
About this image
Scientific classification e
Kingdom: Animalia
Subkingdom: Eumetazoa
Clade: ParaHoxozoa
Clade: Bilateria
Clade: Nephrozoa
(unranked): Protostomia
Superphylum: Ecdysozoa
(unranked): Panarthropoda
(unranked): Tactopoda
Phylum: Arthropoda
von Siebold, 1848[1]
Subphyla, unplaced genera, and classes
Diversity
around 1,170,000 species.
Synonyms

Condylipoda Latreille, 1802

Arthropods (

mineralised with calcium carbonate. The arthropod body plan consists of segments, each with a pair of appendages. Arthropods are bilaterally symmetrical and their body possesses an external skeleton. In order to keep growing, they must go through stages of moulting, a process by which they shed their exoskeleton to reveal a new one. Some species have wings
. They are an extremely diverse group, with up to 10 million species.

The

ganglia in each segment. Their heads are formed by fusion of varying numbers of segments, and their brains are formed by fusion of the ganglia of these segments and encircle the esophagus. The respiratory and excretory systems of arthropods vary, depending as much on their environment as on the subphylum
to which they belong.

Arthropods use combinations of

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, but many species give birth to live young after the eggs have hatched inside the mother, and 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

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

gen. podos (ποδός)), i.e. "foot" or "leg", which together mean "jointed leg".[11] The designation "Arthropoda" was coined in 1848 by the German physiologist and zoologist Karl Theodor Ernst von Siebold (1804–1885).[12][13]

In common parlance, terrestrial arthropods are often called bugs.

true bugs", insects of the order Hemiptera[16]
(which does not include ants, bees, beetles, butterflies or moths).

Description

Arthropods are invertebrates with segmented bodies and jointed limbs.[17] The exoskeleton or cuticles consists of chitin, a polymer of glucosamine.[18] The cuticle of many crustaceans, beetle mites, 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.[19]

Diversity

Estimates of the number of arthropod species vary between 1,170,000 and 5 to 10 million and account for over 80 percent of all known living animal species.[20][21] The 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.[22]

They are important members of marine, freshwater, land and air

malacostracans are much larger; for example, the legs of the Japanese spider crab may span up to 4 metres (13 ft),[24] with the heaviest of all living arthropods being the American lobster
, topping out at over 20 kg (44 lbs).

Segmentation

_______________________
_______________________
_______________________
Segments and tagmata of an arthropod[23]
biramous appendage.[26]

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.[23]

The three-part appearance of many insect bodies and the two-part appearance of spiders is a result of this grouping;[27] in fact there are no external signs of segmentation in mites.[23] 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,[23][28] 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

trilobites have another segmented branch known as exopods, but whether these structures have a single origin remain controversial.[31][32][26] In some segments of all known arthropods the appendages have been modified, for example to form gills, mouth-parts, antennae for collecting information,[27] or claws for grasping;[33] arthropods are "like Swiss Army knives, each equipped with a unique set of specialized tools."[23] 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.[23]

Alignment of anterior body segments and appendages across various arthropod taxa, based on the observations until mid 2010s. Head regions in black.[28][34]

The most conspicuous specialization of segments is in the head. The four major groups of arthropods –

Trilobita – have heads formed of various combinations of segments, with appendages that are missing or specialized in different ways.[23] 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.[35]

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".[36] In 1960, R. E. Snodgrass even hoped it would not be solved, as he found trying to work out solutions to be fun.[Note 2]

Exoskeleton

Arthropod exoskeletons are made of

procuticle.[38] 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.[23]

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.[39] Biomineralization generally affects the exocuticle and the outer part of the endocuticle.[38] Two recent hypotheses about the evolution of biomineralization in arthropods and other groups of animals propose that it provides tougher defensive armor,[40] and that it allows animals to grow larger and stronger by providing more rigid skeletons;[41] and in either case a mineral-organic composite exoskeleton is cheaper to build than an all-organic one of comparable strength.[41][42]

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

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.[23]

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;[43] for example, all spiders extend their legs hydraulically and can generate pressures up to eight times their resting level.[44]

Moulting

The exoskeleton cannot stretch and thus restricts growth. Arthropods, therefore, replace their exoskeletons by undergoing ecdysis (moulting), or shedding the old exoskeleton after growing a new one that is not yet hardened. Moulting cycles run nearly continuously until an arthropod reaches full size.[45]

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

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.[45]

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.[45]

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.

hemocoel, a cavity that runs most of the length of the body and through which blood flows.[46]

Respiration and circulation

Arthropods have open

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.[46]

The heart is typically 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

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.[46]

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.[47] 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.[48]

Nervous system

Living arthropods have paired main nerve cords running along their bodies below the gut, and in each segment the cords form 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").[49]

Excretory system

There are two different types of arthropod excretory systems. In aquatic arthropods, the end-product of biochemical reactions that

nephridia ("little kidneys"), which extract other wastes for excretion as urine.[50]

Senses

The stiff

auditory ossicles. The antennae of most hexapods include sensor packages that monitor humidity, moisture and temperature.[51]

Most arthropods lack balance and

malacostracan crustaceans have statocysts, which provide the same sort of information as the balance and motion sensors of the vertebrate inner ear.[51]

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.[51]

Optical

Most arthropods have sophisticated visual systems that include one or more usually both of

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,[51] and those of jumping spiders can rotate to track prey.[52]

Compound eyes consist of fifteen to several thousand independent

Olfaction

Reproduction and development

A few arthropods, such as

hermaphroditic, that is, each can have the organs of both sexes. However, individuals of most species remain of one sex their entire lives.[54] 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.[55] The ability to undergo meiosis is widespread among arthropods including both those that reproduce sexually and those that reproduce parthenogenetically.[56] Although meiosis is a major characteristic of arthropods, understanding of its fundamental adaptive benefit has long been regarded as an unresolved problem,[57]
that appears to have remained unsettled.

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.[54]

penaeid shrimp

Most arthropods lay eggs,

nauplius larvae that have only three segments and pairs of appendages.[54]

Evolutionary history

Last common ancestor

Based on the distribution of shared

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.[61] However, whether the ancestral limb was uniramous or biramous
is far from a settled debate. This Ur-arthropod had a
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,[61] 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.[62]

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,[63][64][65] but later study shows that their affinities of being origin of arthropods are not reliable.[66] 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.[67][68][69][70] The earliest Cambrian trilobite fossils are about 530 million years old, but the class was already quite diverse and worldwide, suggesting that they had been around for quite some time.[71] In the Maotianshan shales, which date to between 530 and 520 million years ago, fossils of arthropods such as Kylinxia and Erratus have been found that seem to show a transitional split between lobopodia and other more primitive stem arthropods.[72][30] 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.[73][74][75] A fossil of Marrella from the Burgess Shale has provided the earliest clear evidence of moulting.[76]

The earliest fossil crustaceans date from about 511 million years ago in the Cambrian,[77] and fossil shrimp from about 500 million years ago apparently formed a tight-knit procession across the seabed.[78] Crustacean fossils are common from the Ordovician period onwards.[79] They have remained almost entirely aquatic, possibly because they never developed excretory systems that conserve water.[50] In 2020 scientists announced the discovery of Kylinxia, a five-eyed ~5 cm long shrimp-like animal living 518 Mya that – with multiple distinctive features – appears to be a key ‘missing link’ of the evolution from Anomalocaris to true arthropods and could be at the evolutionary root of true arthropods.[72][2]

Arthropods provide the earliest identifiable fossils of land animals, from about 419 million years ago in the Late Silurian,[47] and terrestrial tracks from about 450 million years ago appear to have been made by arthropods.[80] 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.[81] 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).[82]

The oldest known

spinnerets means it was not one of the true spiders,[85] which first appear in the Late Carboniferous over 299 million years ago.[86] The Jurassic and Cretaceous periods provide a large number of fossil spiders, including representatives of many modern families.[87] Fossils of aquatic scorpions with gills appear in the Silurian and Devonian periods, and the earliest fossil of an air-breathing scorpion with book lungs dates from the Early Carboniferous period.[88]

The oldest possible insect fossil is 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.[91]

Evolutionary family tree

velvet worm (Onychophora) is closely related to arthropods[92]

From 1952 to 1977, zoologist

uniramous limbs in which the single branch serves as a leg.[93]

onychophorans,
including Aysheaia and Peripatus

armored

lobopods,
including Hallucigenia and Microdictyon

anomalocarid-like taxa,
including modern tardigrades as
well as extinct animals like
Kerygmachela and Opabinia

Anomalocaris

arthropods,
including living groups and
extinct forms such as trilobites

Simplified summary of Budd's "broad-scale" cladogram (1996)
[92]

Further analysis and discoveries in the 1990s reversed this view, and led to acceptance that arthropods are

lobopods", and he presented an "evolutionary family tree" that showed these as "aunts" and "cousins" of all arthropods.[92][96] 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").[97]

A contrary view was presented in 2003, when Jan Bergström and Xian-Guang Hou 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.[98] In 2014, research indicated that tardigrades were more closely related to arthropods than velvet worms.[99]

Protostomes

Chaetognatha

molluscs, brachiopods
, etc.)

Ecdysozoa

Nematoida (nematodes and close relatives)

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.,
[100] including euthycarcinoids[101]

Higher up the "family tree", the

priapulids and tardigrades
, but these remained minority views because it was difficult to specify in detail the relationships between these groups.

In the 1990s,

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.[102][100]

Phylogeny of stem-group arthropods

Modern interpretations of the basal, extinct

stem-group of Arthropoda recognised the following groups, from most basal to most crownward:[1][103]

The

deutocerebral appendage pair.[1]

However, recent analyses since late 2010s also show that these "upper stem-groups" might be inside the crown-group:

Chelicerates,[104][105] some bivalved forms such as Hymenocarina are consistently shown to be mandibulates,[103] and similarly Fuxianhuiida might also be mandibulates as well.[106]

The following cladogram shows the probable relationships between crown-group Arthropoda and stem-group Arthropoda according to O’Flynn et al. 2022, including two new fossils found to be the most early branches of Deuteropoda[104][105] (the "upper stem-groups" in previous studies[1] are marked in asterisk, living groups are marked in bold):

Panarthropoda

Onychophora

Tardigrada

"Lobopodia"

Arthropoda

Siberion

Megadictyon

Jianshanopodia

Kerygmachela

Pambdelurion

Opabinia

Radiodonta

Deuteropoda

Kylinxia

Fengzhengia

Chelicerata

Megacheira *

'great appendage' bivalved forms *

Isoxyida *

Artiopoda

Mandibulata

Euthycarcinoidea

Fuxianhuiida *

Myriapoda

Hymenocarina *

Pancrustacea

total‑group

Note that the subphylum

trilobites, is closer to mandibulates than to chelicerates in the cladogram above,[104][105] but older analyses place them as the sister group of chelicerates[103] united under the clade Arachnomorpha
.

Phylogeny of living arthropods

The following cladogram shows the internal relationships between all the living classes of arthropods as of late 2010s,[107][108] as well as the estimated timing for some of the clades:[109]

Arthropoda
Chelicerata

Pycnogonida

Euchelicerata

Xiphosura

Arachnida

Mandibulata
Myriapoda

Chilopoda

Progoneata
Edafopoda

Symphyla

Pauropoda

Diplopoda

Pancrustacea
Oligostraca

Ostracoda

Mystacocarida

Ichthyostraca

Branchiura

Pentastomida

Altocrustacea
Multicrustacea
Hexanauplia

Copepoda

Tantulocarida

Thecostraca

Malacostraca

Allotriocarida

Cephalocarida

Athalassocarida

Branchiopoda

Labiocarida

Remipedia

Hexapoda
Elliplura

Collembola

Protura

Cercophora

Diplura

Insecta

440 mya
470 mya
493 mya

Classification

The phylum Arthropoda is typically

extinct:[110]

  1. trilobites
    .
  2. harvestmen, spiders, scorpions and related organisms characterized by the presence of chelicerae, appendages just above/in front of the mouthparts. Chelicerae appear in scorpions and horseshoe crabs as tiny claws that they use in feeding, but those of spiders have developed as fangs
    that inject venom.
  3. body segments
    each of which bearing one or two pairs of legs (or in a few cases being legless). All members are exclusively terrestrial.
  4. legs.

Aside from these major groups, 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.[35]

The phylogeny of the major extant arthropod groups has been an area of considerable interest and dispute.[111] Recent studies strongly suggest that Crustacea, as traditionally defined, is paraphyletic, with Hexapoda having evolved from within it,[112][113] so that Crustacea and Hexapoda form a clade, Pancrustacea. The position of Myriapoda, Chelicerata and Pancrustacea remains unclear as of April 2012. In some studies, Myriapoda is grouped with Chelicerata (forming Myriochelata);[114][115] in other studies, Myriapoda is grouped with Pancrustacea (forming Mandibulata),[112] or Myriapoda may be sister to Chelicerata plus Pancrustacea.[113]

Panarthropoda

Onychophora

Tactopoda

Tardigrada

Euarthropoda

Chelicerata

Mandibulata

Myriapoda

Pancrustacea

Ostracoda, Branchiura, Pentastomida, Mystacocarida

Copepoda, Malacostraca, Thecostraca

Branchiopoda, Cephalocarida

Hexapoda, Remipedia

traditional
Crustacea
Phylogenetic relationships of the major extant arthropod groups according to Regier et al. (2010);[112] traditional subphyla in bold

The placement of the extinct trilobites is also a frequent subject of dispute.[116] One of the newer hypotheses is that the chelicerae have originated from the same pair of appendages that evolved into antennae in the ancestors of Mandibulata, which would place trilobites, which had antennae, closer to Mandibulata than Chelicerata.[117]

Since the

better source needed
]

Subphyla Classes Members Example species
Chelicerata
Arachnida
etc.
Araneae
)
Myriapoda
Chilopoda
Scolopendromorphs
, etc.
Diplopoda, Spirostreptida
)
Crustacea

Clam Shrimp
Remipedes

Ocypode ceratophthalma
(Malacostraca, Decapoda
)
Hexapoda
Insecta
Entognatha
Springtails
, etc.
Insecta, Lepidoptera
)

Interaction with humans

Insects and scorpions on sale in a food stall in Bangkok
, Thailand

butterfly conservatories
, educational exhibits, schools, research facilities, and cultural events.

However, the greatest contribution of arthropods to human food supply is by pollination: a 2008 study examined the 100 crops that FAO lists as grown for food, and estimated pollination's economic value as €153 billion, or 9.5 per cent of the value of world agricultural production used for human food in 2005.[131] Besides pollinating, bees produce honey, which is the basis of a rapidly growing industry and international trade.[132]

The red dye

spinal meningitis and some cancers.[136] Forensic entomology uses evidence provided by arthropods to establish the time and sometimes the place of death of a human, and in some cases the cause.[137] Recently insects have also gained attention as potential sources of drugs and other medicinal substances.[138]

The relative simplicity of the arthropods' body plan, allowing them to move on a variety of surfaces both on land and in water, have made them useful as models for

biomimetic robots to move normally even with damaged or lost appendages.[139][140]

Diseases transmitted by insects
Disease[141] Insect Cases per year Deaths per year
Malaria Anopheles mosquito 267 M 1 to 2 M
Dengue fever Aedes mosquito ? ?
Yellow fever Aedes mosquito 4,432 1,177
Filariasis Culex mosquito 250 M unknown

Although arthropods are the most numerous phylum on Earth, and thousands of arthropod species are venomous, they inflict relatively few serious bites and stings on humans. Far more serious are the effects on humans of diseases like

Many species of arthropods, principally insects but also mites, are agricultural and forest pests.

Predatory mites may be useful in controlling some mite pests.[149][150]

As predators

Even amongst arthropods usually thought of as obligate

biocontrol of Ephestia kuehniella) could survive on flowers but never completed the life cycle, so a meta-analysis[151] was done to find such an overall trend in previously published data, if it existed. In some cases floral resources are outright necessary.[151] Overall, floral resources (and an imitation, i.e. sugar water) increase longevity and fecundity, meaning even predatory population numbers can depend on non-prey food abundance.[151] Thus biocontrol success may surprisingly depend on nearby flowers.[151]

See also

Notes

  1. pillbugs),[15] but argues that "including legless creatures such as worms, slugs, and snails among the bugs stretches the word too much".[16]
  2. ^ "It would be too bad if the question of head segmentation ever should be finally settled; it has been for so long such fertile ground for theorizing that arthropodists would miss it as a field for mental exercise."[37]
  3. ^ The fossil was originally named Eotarbus but was renamed when it was realized that a Carboniferous arachnid had already been named Eotarbus.[84]
  4. ^ For a mention of insect contamination in an international food quality standard, see sections 3.1.2 and 3.1.3 of Codex 152 of 1985 of the Codex Alimentarius[127]
  5. ^ For examples of quantified acceptable insect contamination levels in food see the last entry (on "Wheat Flour") and the definition of "Extraneous material" in Codex Alimentarius,[128] and the standards published by the FDA.[129]

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Bibliography

External links