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Kinorhyncha

Kinorhyncha /knˈrɪŋkə, kɪnə-/ (Ancient Greek: κινέω, romanizedkīnéō, lit.'I move', ῥύγχος rhúnkhos "snout") is a phylum of small marine invertebrates that are widespread in mud or sand at all depths as part of the meiobenthos. They are commonly called mud dragons. Modern species are 1 mm (0.039 in) or less, but Cambrian forms could reach 4 cm (1.6 in).[2]

Kinorhyncha
Temporal range: Early Cambrian–Recent[1]
Echinoderes hwiiza
Scientific classification
Domain: Eukaryota
Kingdom: Animalia
Clade: Bilateria
Clade: Nephrozoa
(unranked): Protostomia
Superphylum: Ecdysozoa
Clade: Scalidophora
Phylum: Kinorhyncha
Reinhard, 1881
Orders

See text

Anatomy edit

Living Echinoderes specimen, showing movement and head retraction

Kinorhynchs are limbless animals, with a body consisting of a head, neck, and a trunk of eleven segments. They are the only members of Ecdysozoa, except from the panarthropoda, with a segmented body. Juveniles have eight or nine segments, depending on genus, with the last two or three being added later during growth.[3] Like other ecdysozoans they do not have external cilia, but instead have a number of spines along the body, plus up to seven circles of spines around the head.[4] These spines are used for locomotion, withdrawing the head and pushing forward, then gripping the substrate with the spines while drawing up the body.

The body wall consists of a thin syncitial layer, which secretes a tough cuticle; this is molted several times while growing to adulthood. The spines are essentially moveable extensions of the body wall, and are hollow and covered by cuticle. The head is completely retractable, and is covered by a set of neck plates called placids when retracted.[5]

Myoanatomy of the body of Echinoderes spinifurca

Kinorhynchs eat either diatoms or organic material found in the mud, depending on species. The mouth is located in a conical structure at the apex of the head, and opens into a pharynx and then an oesophagus, both of which are lined by cuticle. Two pairs of salivary glands and one or more pairs of "pancreatic glands" connect to the oesophagus and presumably secrete digestive enzymes. Beyond the oesophagus lies a midgut that combines the functions of a stomach and intestine, and lacks a cuticle, enabling it to absorb nutrients. The short hind-gut is lined by cuticle, and empties into an anus at the posterior end of the trunk.[5]

There is no circulatory system, although the body cavity (pseudocoelom) is well developed, and includes amoebocytes. The excretory system consists of two protonephridia emptying through pores in the final segment.[5]

Echinoderes close up head anatomy

The nervous system consists of a ventral nerve cord, with one ganglion in each segment, and an anterior nerve ring surrounding the pharynx. Smaller ganglia are also located in the lateral and dorsal portions of each segment, but do not form distinct cords. Some species have simple ocelli on the head, and all species have tiny bristles on the body to provide a sense of touch.[5]

Reproduction edit

There are two sexes that look alike, although some sexual dimorphism in allometry has been reported.[6] A pair of gonads are located in the mid-region of the trunk, and open to pores in the final segment. In most species, the sperm duct includes two or three spiny structures that presumably aid in copulation, although the details are unknown. Individual spermatozoa can reach a quarter of the total body length.[7] The larvae are free-living, but little else is known of their reproductive process.[5] After having laid an egg, the female packs it into a protective envelope of mud and organic material.[8]

Classification edit

Their closest relatives are thought to be the phyla Loricifera and Priapulida. Together they constitute the Scalidophora.

Taxonomy edit

The two groups of Kinorhynchs are generally characterized as classes in Sørensen et al. (2015).[9] 270 species have been described and this number is expected to increase substantially.[10][11] Morphological data has been collected for systematic phylogeny from dozens, and the integration of this with molecular data has led to a new systematic paradigm featuring the order Allomalorhagida (with Homalorhagida being retired).[9] Phylogenomic data has shown Allomalorhagida and Cyclorhagida to be divided in three and two major clades respectively.[12]

The oldest known species is Eokinorhynchus from the Fortunian of China.[13]

Phylum Kinorhyncha

References edit

  1. ^ "Armored kinorhynch-like scalidophoran animals from the early Cambrian". Nature. 26 November 2015. doi:10.1038/srep16521. hdl:10919/74307. Retrieved 10 February 2024.
  2. ^ "'Mindblowing' haul of fossils over 500m years old unearthed in China". The Guardian. 21 March 2019.
  3. ^ Herranz, M.; Park, T.; Di Domenico, M.; Leander, B. S.; Sørensen, M. V.; Worsaae, K. (2021). "Revisiting kinorhynch segmentation: Variation of segmental patterns in the nervous system of three aberrant species". Frontiers in Zoology. 18 (1): 54. doi:10.1186/s12983-021-00438-5. PMC 8529749. PMID 34674731.
  4. ^ Brusca, Richard C; Brusca, Gary J (2003). Invertebrates. Sinauer Associates. ISBN 978-0-87893-097-5. page 347
  5. ^ a b c d e Barnes, Robert D. (1982). Invertebrate Zoology. Philadelphia, PA: Holt-Saunders International. pp. 286–288. ISBN 978-0-03-056747-6.
  6. ^ Cepeda, Diego; Álamo, David; Sánchez, Nuria; Pardos, Fernando (December 2019). "Allometric growth in meiofaunal invertebrates: do all kinorhynchs show homogeneous trends?". Zoological Journal of the Linnean Society. 187 (4): 1041–1060. doi:10.1093/zoolinnean/zlz083.
  7. ^ Neuhaus, B.; Higgins, R. P. (July 2002). "Ultrastructure, Biology, and Phylogenetic Relationships of Kinorhyncha". Integrative and Comparative Biology. 42 (3): 619–32. doi:10.1093/icb/42.3.619. PMID 21708758.
  8. ^ Meet the mud dragon—the tiny animal that lives on the beach - Phys.org
  9. ^ a b Sørensen, M. V. et al. Phylogeny of Kinorhyncha based on morphology and two molecular loci. PLoS One 10, 1–33 (2015).
  10. ^ Altenburger, Andreas; Rho, Hyun S.; Chang, Cheon Y.; Sørensen, Martin V. (December 2015). "Zelinkaderes yong sp. nov. from Korea – the first recording of Zelinkaderes (Kinorhyncha: Cyclorhagida) in Asia". Zoological Studies. 54 (25): e25. doi:10.1186/s40555-014-0103-6. PMC 6661445. PMID 31966112.
  11. ^ "Species list of Kinorhyncha - Hiroshi Yamasaki website". sites.google.com. Retrieved 2018-09-20.
  12. ^ Herranz, Maria; et al. (March 2022). "Phylogenomic analyses of mud dragons (Kinorhyncha)" (PDF). Molecular Phylogenetics and Evolution. 168: 107375. doi:10.1016/j.ympev.2021.107375. PMID 34952205. S2CID 245419318.
  13. ^ Zhang, Huaqiao; Xiao, Shuhai; Liu, Yunhuan; Yuan, Xunlai; Wan, Bin; Muscente, A. D.; Shao, Tiequan; Gong, Hao; Cao, Guohua (December 2015). "Armored kinorhynch-like scalidophoran animals from the early Cambrian". Scientific Reports. 5 (1): 16521. Bibcode:2015NatSR...516521Z. doi:10.1038/srep16521. ISSN 2045-2322. PMC 4660871. PMID 26610151.

External links edit

  •   Media related to Kinorhyncha at Wikimedia Commons
  • Introduction to the Cephalorhyncha
  • Drawings of Kinorhyncha
  • "Kinorhyncha" at the Encyclopedia of Life  

kinorhyncha, dragon, redirects, here, confused, with, chinese, alligator, also, known, muddy, dragon, help, expand, this, article, with, text, translated, from, corresponding, article, german, february, 2009, click, show, important, translation, instructions, . Mud dragon redirects here Not to be confused with the Chinese alligator also known as the muddy dragon You can help expand this article with text translated from the corresponding article in German February 2009 Click show for important translation instructions View a machine translated version of the German article Machine translation like DeepL or Google Translate is a useful starting point for translations but translators must revise errors as necessary and confirm that the translation is accurate rather than simply copy pasting machine translated text into the English Wikipedia Consider adding a topic to this template there are already 9 155 articles in the main category and specifying topic will aid in categorization Do not translate text that appears unreliable or low quality If possible verify the text with references provided in the foreign language article You must provide copyright attribution in the edit summary accompanying your translation by providing an interlanguage link to the source of your translation A model attribution edit summary is Content in this edit is translated from the existing German Wikipedia article at de Hakenrussler see its history for attribution You may also add the template Translated de Hakenrussler to the talk page For more guidance see Wikipedia Translation Kinorhyncha k aɪ n oʊ ˈ r ɪ ŋ k e k ɪ n e Ancient Greek kinew romanized kineō lit I move ῥygxos rhunkhos snout is a phylum of small marine invertebrates that are widespread in mud or sand at all depths as part of the meiobenthos They are commonly called mud dragons Modern species are 1 mm 0 039 in or less but Cambrian forms could reach 4 cm 1 6 in 2 KinorhynchaTemporal range Early Cambrian Recent 1 PreꞒ Ꞓ O S D C P T J K Pg N Echinoderes hwiiza Scientific classification Domain Eukaryota Kingdom Animalia Clade Bilateria Clade Nephrozoa unranked Protostomia Superphylum Ecdysozoa Clade Scalidophora Phylum KinorhynchaReinhard 1881 Orders See text Contents 1 Anatomy 1 1 Reproduction 2 Classification 2 1 Taxonomy 3 References 4 External linksAnatomy edit source source source source source source source Living Echinoderes specimen showing movement and head retraction Kinorhynchs are limbless animals with a body consisting of a head neck and a trunk of eleven segments They are the only members of Ecdysozoa except from the panarthropoda with a segmented body Juveniles have eight or nine segments depending on genus with the last two or three being added later during growth 3 Like other ecdysozoans they do not have external cilia but instead have a number of spines along the body plus up to seven circles of spines around the head 4 These spines are used for locomotion withdrawing the head and pushing forward then gripping the substrate with the spines while drawing up the body The body wall consists of a thin syncitial layer which secretes a tough cuticle this is molted several times while growing to adulthood The spines are essentially moveable extensions of the body wall and are hollow and covered by cuticle The head is completely retractable and is covered by a set of neck plates called placids when retracted 5 source source source source source Myoanatomy of the body of Echinoderes spinifurca Kinorhynchs eat either diatoms or organic material found in the mud depending on species The mouth is located in a conical structure at the apex of the head and opens into a pharynx and then an oesophagus both of which are lined by cuticle Two pairs of salivary glands and one or more pairs of pancreatic glands connect to the oesophagus and presumably secrete digestive enzymes Beyond the oesophagus lies a midgut that combines the functions of a stomach and intestine and lacks a cuticle enabling it to absorb nutrients The short hind gut is lined by cuticle and empties into an anus at the posterior end of the trunk 5 There is no circulatory system although the body cavity pseudocoelom is well developed and includes amoebocytes The excretory system consists of two protonephridia emptying through pores in the final segment 5 source source source source source Echinoderes close up head anatomy The nervous system consists of a ventral nerve cord with one ganglion in each segment and an anterior nerve ring surrounding the pharynx Smaller ganglia are also located in the lateral and dorsal portions of each segment but do not form distinct cords Some species have simple ocelli on the head and all species have tiny bristles on the body to provide a sense of touch 5 Reproduction edit There are two sexes that look alike although some sexual dimorphism in allometry has been reported 6 A pair of gonads are located in the mid region of the trunk and open to pores in the final segment In most species the sperm duct includes two or three spiny structures that presumably aid in copulation although the details are unknown Individual spermatozoa can reach a quarter of the total body length 7 The larvae are free living but little else is known of their reproductive process 5 After having laid an egg the female packs it into a protective envelope of mud and organic material 8 Classification editSee also List of bilaterial animal orders Their closest relatives are thought to be the phyla Loricifera and Priapulida Together they constitute the Scalidophora Taxonomy edit The two groups of Kinorhynchs are generally characterized as classes in Sorensen et al 2015 9 270 species have been described and this number is expected to increase substantially 10 11 Morphological data has been collected for systematic phylogeny from dozens and the integration of this with molecular data has led to a new systematic paradigm featuring the order Allomalorhagida with Homalorhagida being retired 9 Phylogenomic data has shown Allomalorhagida and Cyclorhagida to be divided in three and two major clades respectively 12 The oldest known species is Eokinorhynchus from the Fortunian of China 13 Phylum Kinorhyncha Class Cyclorhagida Zelinka 1896 Chitwood 1951 Order Echinorhagata Sorensen et al 2015 Echinoderidae Zelinka 1894 Order Kentrorhagata Sorensen et al 2015 Antygomonidae Adrianov amp Malakhov 1994 Cateriidae Gerlach 1956 following Sorensen et al Centroderidae Zelinka 1896 Semnoderidae Remane 1929 Zelinkaderidae Higgins 1990 Order Xenosomata Zelinka 1907 Campyloderidae Remane 1929 Class Allomalorhagida Sorensen et al 2015 Pycnophyidae Zelinka 1986 Order Anomoirhaga Herranz et al 2022 Cateriidae Gerlach 1956 following Herranz et al Dracoderidae Higgins amp Shirayama 1990 Franciscideridae Sorensen et al 2015 Neocentrophyidae Higgins 1969References edit Armored kinorhynch like scalidophoran animals from the early Cambrian Nature 26 November 2015 doi 10 1038 srep16521 hdl 10919 74307 Retrieved 10 February 2024 Mindblowing haul of fossils over 500m years old unearthed in China The Guardian 21 March 2019 Herranz M Park T Di Domenico M Leander B S Sorensen M V Worsaae K 2021 Revisiting kinorhynch segmentation Variation of segmental patterns in the nervous system of three aberrant species Frontiers in Zoology 18 1 54 doi 10 1186 s12983 021 00438 5 PMC 8529749 PMID 34674731 Brusca Richard C Brusca Gary J 2003 Invertebrates Sinauer Associates ISBN 978 0 87893 097 5 page 347 a b c d e Barnes Robert D 1982 Invertebrate Zoology Philadelphia PA Holt Saunders International pp 286 288 ISBN 978 0 03 056747 6 Cepeda Diego Alamo David Sanchez Nuria Pardos Fernando December 2019 Allometric growth in meiofaunal invertebrates do all kinorhynchs show homogeneous trends Zoological Journal of the Linnean Society 187 4 1041 1060 doi 10 1093 zoolinnean zlz083 Neuhaus B Higgins R P July 2002 Ultrastructure Biology and Phylogenetic Relationships of Kinorhyncha Integrative and Comparative Biology 42 3 619 32 doi 10 1093 icb 42 3 619 PMID 21708758 Meet the mud dragon the tiny animal that lives on the beach Phys org a b Sorensen M V et al Phylogeny of Kinorhyncha based on morphology and two molecular loci PLoS One 10 1 33 2015 Altenburger Andreas Rho Hyun S Chang Cheon Y Sorensen Martin V December 2015 Zelinkaderes yong sp nov from Korea the first recording of Zelinkaderes Kinorhyncha Cyclorhagida in Asia Zoological Studies 54 25 e25 doi 10 1186 s40555 014 0103 6 PMC 6661445 PMID 31966112 Species list of Kinorhyncha Hiroshi Yamasaki website sites google com Retrieved 2018 09 20 Herranz Maria et al March 2022 Phylogenomic analyses of mud dragons Kinorhyncha PDF Molecular Phylogenetics and Evolution 168 107375 doi 10 1016 j ympev 2021 107375 PMID 34952205 S2CID 245419318 Zhang Huaqiao Xiao Shuhai Liu Yunhuan Yuan Xunlai Wan Bin Muscente A D Shao Tiequan Gong Hao Cao Guohua December 2015 Armored kinorhynch like scalidophoran animals from the early Cambrian Scientific Reports 5 1 16521 Bibcode 2015NatSR 516521Z doi 10 1038 srep16521 ISSN 2045 2322 PMC 4660871 PMID 26610151 External links edit nbsp Media related to Kinorhyncha at Wikimedia Commons Introduction to the Cephalorhyncha Drawings of Kinorhyncha Kinorhyncha at the Encyclopedia of Life nbsp Retrieved from https en wikipedia org w index php title Kinorhyncha amp oldid 1206438391, wikipedia, wiki, book, books, library,

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