Global InformationArthropod information
| Arthropoda Temporal range: Earliest Cambrian (Fortunian)–Recent
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Scientific classification 
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Subkingdom: | Eumetazoa |
| Clade: | ParaHoxozoa |
| Clade: | Bilateria |
| Clade: | Nephrozoa |
| (unranked): | Protostomia |
| Superphylum: | Ecdysozoa |
| (unranked): | Panarthropoda |
| (unranked): | Tactopoda |
| Phylum: | Arthropoda Gravenhorst, 1843[1][2] |
| Subphyla, unplaced genera, and classes | |
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| Diversity | |
| around 1,170,000 species. | |
| Synonyms | |
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Condylipoda Latreille, 1802 | |
Arthropods (/ˈɑːrθrəpɒd/) are invertebrates in the phylum Arthropoda. They possess an exoskeleton with a cuticle made of chitin, often mineralised with calcium carbonate, a body with differentiated (metameric) segments, and paired jointed appendages. 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. They are an extremely diverse group, with up to 10 million species.
Haemolymph is the analogue of blood for most arthropods. An arthropod has an open circulatory system, with a body cavity called a haemocoel through which haemolymph circulates to the interior organs. 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.
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.
- ^ Martínez-Muñoz, Carlos A. (4 May 2023). "The correct authorship of Arthropoda—A reappraisal". Integrative Systematics. 6 (1): 1–8. doi:10.18476/2023.472723. ISSN 2628-2380. S2CID 258497632.
- ^ Gravenhorst, J. L. C. (1843). Vergleichende Zoologie. Breslau: Druck und Verlag von Graß, Barth und Comp.
- ^ Moysiuk J, Caron JB (January 2019). "Burgess Shale fossils shed light on the agnostid problem". Proceedings. Biological Sciences. 286 (1894): 20182314. doi:10.1098/rspb.2018.2314. PMC 6367181. PMID 30963877.
- ^ Fu, D.; Legg, D. A.; Daley, A. C.; Budd, G. E.; Wu, Y.; Zhang, X. (2022). "The evolution of biramous appendages revealed by a carapace-bearing Cambrian arthropod". Philosophical Transactions of the Royal Society B: Biological Sciences. 377 (1847): Article ID 20210034. doi:10.1098/rstb.2021.0034. PMC 8819368. PMID 35125000.
- ^ O'Flynn, Robert J.; Williams, Mark; Yu, Mengxiao; Harvey, Thomas; Liu, Yu (2022). "A new euarthropod with large frontal appendages from the early Cambrian Chengjiang biota". Palaeontologia Electronica. 25 (1): 1–21. doi:10.26879/1167. S2CID 246779634.
- ^ a b Cite error: The named reference
Kylinxiawas invoked but never defined (see the help page). - ^ Legg, David A.; Sutton, Mark D.; Edgecombe, Gregory D. (30 September 2013). "Arthropod fossil data increase congruence of morphological and molecular phylogenies". Nature Communications. 4 (1): 2485. Bibcode:2013NatCo...4.2485L. doi:10.1038/ncomms3485. ISSN 2041-1723. PMID 24077329.
- ^ Pulsipher, M. A.; Anderson, E. P.; Wright, L. S.; Kluessendorf, J.; Mikulic, D. G.; Schiffbauer, J. D. (2022). "Description of Acheronauta gen. nov., a possible mandibulate from the Silurian Waukesha Lagerstätte, Wisconsin, USA". Journal of Systematic Palaeontology. 20 (1). 2109216. doi:10.1080/14772019.2022.2109216. S2CID 252839113.
- ^ Clark, Neil D L; Feldmann, Rodney M; Schram, Frederick R; Schweitzer, Carrie E (2020). "Redescription of Americlus rankini (Woodward, 1868) (Pancrustacea: Cyclida: Americlidae) and interpretation of its systematic placement, morphology, and paleoecology" (PDF). Journal of Crustacean Biology. 40 (2): 181–193. doi:10.1093/jcbiol/ruaa001.
- ^ Peel, J.S.; Stein, M. "A new Arthropod from the Lower Cambrian Sirius Passet Fossil-Lagerstätten of North Greenland" (PDF). Bulletin of Geosciences. 84 (4): 1158.
- ^ Edgecombe, Gregory D. (1 September 2017). "Inferring Arthropod Phylogeny: Fossils and their Interaction with Other Data Sources". Integrative and Comparative Biology. 57 (3): 467–476. doi:10.1093/icb/icx061. ISSN 1540-7063. PMID 28957518.
- ^ Garwood, R.; Sutton, M. (18 February 2012), "The enigmatic arthropod Camptophyllia", Palaeontologia Electronica, 15 (2): 12, doi:10.1111/1475-4983.00174, archived (PDF) from the original on 2 December 2013, retrieved 11 June 2012
- ^ Zhai, Dayou; Williams, Mark; Siveter, David J.; Siveter, Derek J.; Harvey, Thomas H. P.; Sansom, Robert S.; Mai, Huijuan; Zhou, Runqing; Hou, Xianguang (22 February 2022). "Chuandianella ovata: An early Cambrian stem euarthropod with feather-like appendages". Palaeontologia Electronica. 25 (1): 1–22. doi:10.26879/1172. ISSN 1094-8074. S2CID 247123967.
- ^ Waloszek, Dieter; Müller, Klaus (1 October 1990). "Upper Cambrian stem-lineage crustaceans and their bearing upon the monophyly of Crustacea and the position of Agnostus". Lethaia. 23: 409–427. doi:10.1111/j.1502-3931.1990.tb01373.x.
- ^ Van Roy, Peter; Rak, Štěpán; Budil, Petr; Fatka, Oldřich (13 June 2022). "Redescription of the cheloniellid euarthropod Triopus draboviensis from the Upper Ordovician of Bohemia, with comments on the affinities of Parioscorpio venator". Geological Magazine. 159 (9): 1471–1489. Bibcode:2022GeoM..159.1471V. doi:10.1017/s0016756822000292. hdl:1854/LU-8756253. ISSN 0016-7568. S2CID 249652930.
- ^ Haug, J.T.; Maas, A.; Haug, C.; Waloszek, D. (1 November 2011). "Sarotrocercus oblitus - Small arthropod with great impact on the understanding of arthropod evolution?". Bulletin of Geosciences: 725–736. doi:10.3140/bull.geosci.1283. ISSN 1802-8225.
- ^ Ortega-Hernández, Javier; Legg, David A.; Braddy, Simon J. (2013). "The phylogeny of aglaspidid arthropods and the internal relationships within Artiopoda". Cladistics. 29 (1): 15–45. doi:10.1111/j.1096-0031.2012.00413.x. PMID 34814371. S2CID 85744103.
- ^ Kühl, Gabrielle; Rust, Jes (2009). "Devonohexapodus bocksbergensis is a synonym of Wingertshellicus backesi (Euarthropoda) – no evidence for marine hexapods living in the Devonian Hunsrück Sea". Organisms Diversity & Evolution. 9 (3): 215–231. doi:10.1016/j.ode.2009.03.002.