Arthropod

Arthropods
Temporal range: 540–0 Ma Cambrian–Holocene
Arthropoda.jpg
Extinct and modern arthropods
Scientific classification e
Kingdom:Animalia
Superphylum:Ecdysozoa
(unranked):Panarthropoda
(unranked):Tactopoda
Phylum:Arthropoda
Lankester, 1904[1]
Subphyla, unplaced genera, and classes
Synonyms

Condylipoda Latreille, 1802

An arthropod (d/, from Greek ἄρθρον arthron, "joint" and πούς pous, "foot") is an invertebrate animal having an exoskeleton (external skeleton), a segmented body, and paired jointed appendages. Arthropods form the phylum Euarthropoda,[1][3] which includes insects, arachnids, myriapods, and crustaceans. The term Arthropoda as originally proposed refers to a proposed grouping of Euarthropods and the phylum Onychophora.Arthropods are characterized by their jointed limbs and cuticle made of chitin, often mineralised with calcium carbonate. The arthropod body plan consists of segments, each with a pair of appendages. The rigid cuticle inhibits growth, so arthropods replace it periodically by moulting.

Their versatility has enabled them to become the most species-rich members of all ecological guilds in most environments. They have over a million described species, making up more than 80 per cent of all described living animal species, some of which, unlike most other animals, are very successful in dry environments.

Arthropods range in size from the microscopic crustacean Stygotantulus up to the Japanese spider crab. Arthropods' primary internal cavity is a hemocoel, which accommodates their internal organs, and through which their haemolymph – analogue of blood – circulates; they have open circulatory systems. Like their exteriors, the internal organs of arthropods are generally built of repeated segments. Their nervous system is "ladder-like", with paired ventral nerve cords running through all segments and forming paired 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.

Their vision relies on various combinations of compound eyes and pigment-pit ocelli: 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 setae (bristles) that project through their cuticles. Arthropods' methods of reproduction and development are diverse; all terrestrial species use internal fertilization, but this is often 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 scorpions give birth to live young after the eggs have hatched inside the mother. 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 scorpions.

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 Metazoa are not yet well resolved. Likewise, the relationships between various arthropod groups are still actively debated.

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. podos), i.e. "foot" or "leg", which together mean "jointed leg".[4]

Other Languages
Afrikaans: Geleedpotiges
Alemannisch: Gliederfüßer
አማርኛ: ጋጥመ-ብዙ
aragonés: Arthropoda
asturianu: Arthropoda
Avañe'ẽ: Mymba ipy apytimby
azərbaycanca: Buğumayaqlılar
Bân-lâm-gú: Chat-kha tōng-bu̍t
беларуская: Членістаногія
беларуская (тарашкевіца)‎: Суставаногія
български: Членестоноги
bosanski: Zglavkari
brezhoneg: Arthropoda
буряад: Үетэ хүлтэн
català: Artròpodes
čeština: Členovci
corsu: Arthropoda
Cymraeg: Arthropod
dansk: Leddyr
Ελληνικά: Αρθρόποδα
español: Arthropoda
Esperanto: Artropodoj
euskara: Artropodo
فارسی: بندپایان
Fiji Hindi: Arthropod
føroyskt: Liðadýr
français: Arthropode
Gaeilge: Artrapód
galego: Artrópodos
ગુજરાતી: સંધિપાદ
한국어: 절지동물
हिन्दी: सन्धिपाद
hrvatski: Člankonošci
Ilokano: Artropoda
Bahasa Indonesia: Artropoda
interlingua: Arthropoda
íslenska: Liðdýr
italiano: Arthropoda
Basa Jawa: Arthropoda
қазақша: Буынаяқтылар
kernowek: Melldrosek
Kiswahili: Arithropodi
Kreyòl ayisyen: Atwopòd
kurdî: Girêçikpê
кырык мары: Arthropoda
Latina: Arthropoda
latviešu: Posmkāji
Lëtzebuergesch: Arthropoden
lietuvių: Nariuotakojai
Limburgs: Gelidpoetege
македонски: Членконоги
മലയാളം: ആർത്രോപോഡ
Bahasa Melayu: Artropod
Baso Minangkabau: Arthropoda
монгол: Үет хөлтөн
Nederlands: Geleedpotigen
日本語: 節足動物
Nordfriisk: Laspuateten
norsk: Leddyr
norsk nynorsk: Leddyr
occitan: Arthropoda
oʻzbekcha/ўзбекча: Boʻgʻimoyoqlilar
ਪੰਜਾਬੀ: ਆਰਥਰੋਪੋਡ
پنجابی: ارتھروپوڈ
Plattdüütsch: Liddfööt
polski: Stawonogi
português: Artrópode
română: Artropode
Runa Simi: Sillwichaki
русиньскый: Членистоногы
Scots: Arthropod
sicilianu: Arthropoda
Simple English: Arthropod
slovenčina: Článkonožce
slovenščina: Členonožci
کوردی: گرێپایان
српски / srpski: Зглавкари
srpskohrvatski / српскохрватски: Zglavkari
Basa Sunda: Arthropoda
svenska: Leddjur
Tagalog: Arthropoda
татарча/tatarça: Буынтыкаяклылар
тоҷикӣ: Бандпойҳо
lea faka-Tonga: Veʻehokohoko
українська: Членистоногі
West-Vlams: Geleedpôtign
Winaray: Arthropoda
ייִדיש: ארטראפאד
粵語: 節肢動物
中文: 节肢动物
Lingua Franca Nova: Artropodo