[{"@context":"http:\/\/schema.org\/","@type":"BlogPosting","@id":"https:\/\/wiki.edu.vn\/en\/wiki40\/larvacean-wikipedia\/#BlogPosting","mainEntityOfPage":"https:\/\/wiki.edu.vn\/en\/wiki40\/larvacean-wikipedia\/","headline":"Larvacean – Wikipedia","name":"Larvacean – Wikipedia","description":"Class of marine animals in the subphylum Tunicata Appendicularia Oikopleura dioica Houses of Bathochordaeus charon and B. stygius Scientific classification","datePublished":"2021-01-12","dateModified":"2021-01-12","author":{"@type":"Person","@id":"https:\/\/wiki.edu.vn\/en\/wiki40\/author\/lordneo\/#Person","name":"lordneo","url":"https:\/\/wiki.edu.vn\/en\/wiki40\/author\/lordneo\/","image":{"@type":"ImageObject","@id":"https:\/\/secure.gravatar.com\/avatar\/c9645c498c9701c88b89b8537773dd7c?s=96&d=mm&r=g","url":"https:\/\/secure.gravatar.com\/avatar\/c9645c498c9701c88b89b8537773dd7c?s=96&d=mm&r=g","height":96,"width":96}},"publisher":{"@type":"Organization","name":"Enzyklop\u00e4die","logo":{"@type":"ImageObject","@id":"https:\/\/wiki.edu.vn\/wiki4\/wp-content\/uploads\/2023\/08\/download.jpg","url":"https:\/\/wiki.edu.vn\/wiki4\/wp-content\/uploads\/2023\/08\/download.jpg","width":600,"height":60}},"image":{"@type":"ImageObject","@id":"https:\/\/upload.wikimedia.org\/wikipedia\/commons\/thumb\/5\/52\/Oikopleura_dioica.gif\/220px-Oikopleura_dioica.gif","url":"https:\/\/upload.wikimedia.org\/wikipedia\/commons\/thumb\/5\/52\/Oikopleura_dioica.gif\/220px-Oikopleura_dioica.gif","height":"344","width":"220"},"url":"https:\/\/wiki.edu.vn\/en\/wiki40\/larvacean-wikipedia\/","wordCount":1767,"articleBody":"Class of marine animals in the subphylum TunicataAppendiculariaOikopleura dioicaHouses of Bathochordaeus charon and B. stygiusScientific classification Kingdom:AnimaliaPhylum:ChordataSubphylum:TunicataClass:AppendiculariaFol, 1872[1]Order:CopelataHaeckel, 1866FamiliesKowalevskiidae Lahille, 1888Fritillariidae Seeliger, 1895Oikopleuridae Lohmann, 1896Bathochordaeus Chun, 1900Mesochordaeus Fenaux & Youngbluth, 1990Althoffia Lohmann, 1892Mesoikopleura Fenaux, 1993Pelagopleura Lohmann, 1926Sinisteroffia Tokioka, 1957Chunopleura Lohmann, 1914Folia Lohmann, 1892Megalocercus Chun, 1887Oikopleura Mertens, 1830Stegosoma Chun, 1887SynonymsLarvacea Herdman, 1882Perennichordata Balfour, 1881Larvaceans, class Appendicularia, are solitary, free-swimming tunicates found throughout the world’s oceans. Like most tunicates, larvaceans are filter feeders. Unlike most other tunicates, they live in the pelagic zone, specifically in the photic zone, or sometimes deeper. They are transparent planktonic animals, generally less than 1\u00a0cm (0.39\u00a0in) in body length, excluding the tail.Table of ContentsAnatomy[edit]House[edit]Feeding[edit]Reproduction and genetics[edit]References[edit]Anatomy[edit]The adult larvaceans resemble the tadpole-like larvae of most tunicates. Like a common tunicate larva, the adult Appendicularia have a discrete trunk and tail. It was originally believed that larvaceans were neotenic tunicates, giving them their common name. Recent studies hint at an earlier divergence, with ascidians having developed their sessile adult form later on.The tail of larvaceans contain a central notochord, a dorsal nerve cord, and a series of striated muscle bands enveloped either by epithelial tissue (oikopleurids) or by an acellular basement membrane (fritillarids). Unlike the ascidian larvae, the tail nerve cord in larvaceans contain some neurons.[3]As the larvae of ascidian tunicates don’t feed at all,[4] the larvae of doliolids goes through their metamorphosis while still inside the egg,[5] and salps and pyrosomes have both lost the larval stage,[6] it makes the larvaceans the only tunicates that feed and has fully functional internal organs during their tailed “tadpole stage”, which in Appendicularia is permanent.House[edit]Larvaceans produce a “house” made of mucopolysaccharides and cellulose.[7] In most species, the house surrounds the animal like a bubble. Even for species in which the house does not completely surround the body, such as Fritillaria, the house is always present and attached to at least one surface.The houses possess several sets of filters, with external filters stopping food particles too big for the larvacean to eat, and internal filters redirecting edible particles to the larvacean’s mouth. Including the external filters, the houses can reach over a meter, an order of magnitude larger than the larvacean itself.These houses are discarded and replaced regularly as the animal grows in size and its filters become clogged; in Oikopleura, a house is kept for no more than four hours before being replaced. No other tunicate is able to abandon its test in this fashion. Discarded larvacean houses account for a significant fraction of organic material descending to the ocean depths.[8]Feeding[edit]Larvaceans have greatly improved the efficiency of food intake by producing a test, which contains a complicated arrangement of filters that allow food in the surrounding water to be brought in and concentrated prior to feeding. By regularly beating the tail, the larvacean can generate water currents within its house that allow the concentration of food. The high efficiency of this method allows larvaceans to feed on much smaller nanoplankton than most other filter feeders.Like most tunicates, larvaceans feed by drawing particulate food matter into their pharyngobranchial region, where food particles are trapped on a mucus mesh produced by the pharynx and drawn into the digestive tract. The mucus mesh lies over two clefts in the pharynx, one on either side, rather than the much larger number of clefts found in most other tunicates.Furthermore, the Appendicularia retain the ancestral chordate characteristics of having the clefts, and the anus open directly to the outside, and by the lack of the atrium and the atrial siphon found in related classes.Reproduction and genetics[edit]Larvaceans reproduce sexually. The immature animals resemble the tadpole larvae of ascidians, albeit with the addition of developing viscera. Once the trunk is fully developed, the larva undergoes “tail shift”, in which the tail moves from a rearward position to a ventral orientation and twists 90\u00b0 relative to the trunk. Following tail shift, the larvacean begins secretion of the first house.Fertilisation is external. During egg release the body wall ruptures, killing the animal.[9]The recent development of techniques for expressing foreign genes in Oikopleura dioica, which unlike all other known larvaceans have separate sexes instead of being a protandric hermaphrodite, has led to the advancement of this species as a model organism for the study of gene regulation, chordate evolution, and development.References[edit]Bone, Q. (1998). The Biology of Pelagic Tunicates. Oxford, UK: Oxford University Press.Clarke, T.; Bouquet, JM; Fu, X; Kalles\u00f8e, T.; Schmid, M; Thompson, E.M. (2007). “Rapidly evolving lamins in a chordate, Oikopleura dioica, with unusual nuclear architecture”. Gene. 396 (1): 159\u2013169. doi:10.1016\/j.gene.2007.03.006. PMID\u00a017449201."},{"@context":"http:\/\/schema.org\/","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"item":{"@id":"https:\/\/wiki.edu.vn\/en\/wiki40\/#breadcrumbitem","name":"Enzyklop\u00e4die"}},{"@type":"ListItem","position":2,"item":{"@id":"https:\/\/wiki.edu.vn\/en\/wiki40\/larvacean-wikipedia\/#breadcrumbitem","name":"Larvacean – Wikipedia"}}]}]