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Ascidiacea
Ascidiacea, commonly known as the ascidians or sea squirts, is a paraphyletic class in the subphylum Tunicata of sac-like marine invertebrate filter feeders. Ascidians are characterized by a tough outer test or "tunic" made of the polysaccharide cellulose. Ascidians are found all over the world, usually in shallow water with salinities over 2.5%. While members of the Thaliacea (salps, doliolids and pyrosomes) and Appendicularia (larvaceans) swim freely like plankton, sea squirts are sessile animals after their larval phase: they then remain firmly attached to their substratum, such as rocks and shells. There are 2,300 species of ascidians and three main types: solitary ascidians, social ascidians that form clumped communities by attaching at their bases, and compound ascidians that consist of many small individuals (each individual is called a zooid) forming large colonies. Sea squirts feed by taking in water through a tube, the oral siphon. The water enters the mouth and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tunicate
Tunicates are marine invertebrates belonging to the subphylum Tunicata ( ). This grouping is part of the Chordata, a phylum which includes all animals with dorsal nerve cords and notochords (including vertebrates). The subphylum was at one time called Urochordata, and the term urochordates is still sometimes used for these animals. Despite their simple appearance and very different adult form, their close relationship to the vertebrates is certain. Both groups are chordates, as evidenced by the fact that during their mobile larval stage, tunicates possess a notochord, a hollow dorsal nerve cord, pharyngeal slits, post-anal tail, and an endostyle. They resemble a tadpole. Tunicates are the only chordates that have lost their Myomere, myomeric segmentation, with the possible exception of the seriation of the gill slits. However, Doliolida, doliolids still display segmentation of the muscle bands. Some tunicates live as solitary individuals, but others replicate by budding and be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Larvacean
Larvaceans, copelates or appendicularians, class Appendicularia, are solitary, free-swimming tunicates found throughout the world's oceans. While larvaceans are filter feeders like most other tunicates, they keep their tadpole-like shape as adults, with the notochord running through the tail. They can be found in the pelagic zone, specifically in the photic zone, or sometimes deeper. They are transparent planktonic animals, usually ranging from to in body length including the tail, although giant larvaceans can reach up to in length. Larvaceans are known for the large houses they build around their bodies to assist in filter-feeding. Secreted from mucus and cellulose, these structures often comprise several layers of filters and can reach up to ten times their body length. In some genera like '' Oikopleura'', houses are built and discarded every few hours, with sinking houses playing a key role in the oceanic carbon cycle. History The study of larvaceans began with the d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aplousobranchia
Aplousobranchia is an order of sea squirts in the class Ascidiacea, first described by Fernando Lahille in 1886. They are colonial animals, and are distinguished from other sea squirts by the presence of relatively simple pharyngeal baskets. This provides the etymology of their name: in Ancient Greek, () means "simple". The posterior part of the abdomen contains the heart and gonads, and is typically larger than in other sea squirts. Taxonomy Order Aplousobranchia * Family Clavelinidae Forbes & Hanley 1848 ycnoclavellidae Kott 1990**'' Clavelina'' Savigny 1816 [''Bradiclavella'' Zirpolo 1925; ''Chondrostachys'' Macdonald 1858; ''Dendroclavella'' Oka 1927; ''Podoclavella'' Herdman 1890; ''Rhodozona'' Van Name 1902; ''Stereoclavella'' Herdman 1890; ''Synclavella'' Caullery 1900] **''Euclavella'' Kott 1990 **''Nephtheis'' Gould 1856 [''Oxycorynia'' Drasche 1882] **''Pycnoclavella'' Garstang 1891 [''Archiascidia'' Julin 1904] * Family Diazonidae Garstang 1891 **'' Diazona'' Savig ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phlebobranchia
Phlebobranchia is an order of sea squirts in the class Ascidiacea, first described by Fernando Lahille in 1886. Characteristics The group includes both colonial and solitary animals. They are distinguished from other sea squirts by the presence of longitudinal vessels in the pharyngeal basket. This provides the etymology of their name: in ancient greek, means "blood vessel". Another characteristic of phlebobranchians is the gonad A gonad, sex gland, or reproductive gland is a Heterocrine gland, mixed gland and sex organ that produces the gametes and sex hormones of an organism. Female reproductive cells are egg cells, and male reproductive cells are sperm. The male gon ...s being surrounded by a loop of gut. The posterior part of the abdomen is absent, and many species also lack the epicardial cavity that surrounds the heart and other internal organs in many other sea squirts. Taxonomy * ?† Permosomidae ** ?†'' Permosoma tunicatum'' Jaekel 1915 'Sphaerospongia pe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stolidobranchia
Stolidobranchia is an order of tunicates in the class Ascidiacea.Lambert, G.; Gittenberger, A.; Sanamyan, K. (2015)Stolidobranchia.In: Shenkar, N.; Gittenberger, A.; Lambert, G.; Rius, M.; Moreira Da Rocha, R.; Swalla, B.J.; Turon, X. (2015) Ascidiacea World Database. Accessed through: World Register of Marine Species on 2015-12-23 The group includes both colonial and solitary animals. They are distinguished from other tunicates by the presence of folded pharyngeal baskets. This provides the etymology of their name: in ancient Greek Ancient Greek (, ; ) includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Greek ..., means the "fold" of a cloth. Stolidobranchian sea squirts are also characterized by the complete absence of an abdomen. The abdominal organs of other tunicates are instead located to one side of the p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cheungkongella
''Cheungkongella'' is a fossil organism from the lower Cambrian Chengjiang lagerstatte, the affinity of which has been the subject of debate. It was announced as a "probable" tunicate while noting the lack of definitive Cambrian fossils from that group. However, this affinity was later disputed in a paper announcing the discovery of '' Shankouclava'', also from Chengjiang, as the oldest known tunicate. ''Cheungkongella'' has been accepted as a distinct taxon and possible tunicate by multiple workers not involved in its discovery, but the dispute remains unresolved. Etymology "Cheungkong" is "a metaphor of China" and honors the Cheungkong Scholars Programme's support for the work leading to the fossil's discovery. "Ancestralis" refers to the fossil's possible primitive taxonomic position. Description ''Cheungkongella'' has a club-shaped body similar to the extant ascidian '' Styela'', with a bucket-shaped main body with thick, tapering stem beneath it. A large oral siphon ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ciona Intestinalis
''Ciona intestinalis'' (sometimes known by the common name of vase tunicate) is an ascidian (sea squirt), a tunicate with very soft tunic. Its Latin name literally means "pillar of intestines", referring to the fact that its body is a soft, translucent column-like structure, resembling a mass of intestines sprouting from a rock. It is a globally distributed cosmopolitan species. Since Linnaeus described the species, ''Ciona intestinalis'' has been used as a model invertebrate chordate in developmental biology and genomics. Studies conducted between 2005 and 2010 have shown that there are at least two, possibly four, sister species. More recently it has been shown that one of these species has already been described as '' Ciona robusta''. By anthropogenic means, the species has invaded various parts of the world and is known as an invasive species. Although Linnaeus first categorised this species as a kind of mollusk, Alexander Kovalevsky found a tadpole-like larval stage durin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Burykhia
''Burykhia hunti'' is an Ediacaran fossil from the White Sea region of Russia dating to . It is considered of possibly ascidian affinity, due to the sac-like morphology and a series of distinctly perforated bands reminiscent of a tunicate pharynx. If ''B. hunti'' is a tunicate, it could be the oldest ascidian fossil known as of its publication in 2012. It is also possibly related to the slightly younger '' Ausia'', another putative ascidian from the Vendian biota in Namibia. Discovery and Naming The fossil material of ''Burkyhia'' was found in the Syuzma River of the Ustʹ Pinega Formation, in Arkhangelsk Oblast of Northwestern Russia in 1995 and 2003, and described in 2012. The generic name ''Burykhia'' derives from the Latinised surnames of Andreevna and Timofey Antonovich Burykh, residents who lived near the fossil site that helped with the expedition. The specific name ''hunti'' derives from the surname of Nathan Hunt, who has contributed to the study of Neoproterozoic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thaliacea
Thaliacea is a class of marine chordates within the subphylum Tunicate, Tunicata, comprising the salps, pyrosomes and doliolids. Unlike their benthic relatives the Ascidiacea, ascidians, from which they are believed to have emerged, thaliaceans are free-floating (pelagic) for their entire lifespan. The group includes species with complex life cycles, with both solitary and Colony (biology), colonial forms. Anatomy The three orders of thaliaceans are filter feeders. Pyrosoma, Pyrosomes are colonial animals, with multiple tiny ascidian-like zooids arranged in a cylinder closed at one end. All of the atrial siphons point inwards, emptying into a single, common cloaca in the centre of the cylinder. As the water exhaled by the zooids exits through a common opening, the water movement slowly propels the pyrosome through the sea. Salps and doliolids have a transparent barrel-shaped body through which they pump water, propelling them through the sea, and from which they extract food. The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Substrate (marine Biology)
Substrate is the earthy material that forms or collects at the bottom of an aquatic habitat. It is made of sediments that may consist of: *Silt – A loose, granular material with mineral particles 0.5 mm or less in diameter. *Clay – A smooth, fine-grained material made of fine particles of hydrous aluminium phyllosilicate minerals (such as kaolinite). * Mud – A mixture of water with silt, clay, or loam. *Sand – Mineral particles between 0.06 and 2 mm in diameter. * Granule – Between 2 and 4 mm in diameter. *Pebble – Between 4 – 64 mm in diameter. * Cobble – between 6.4 and 25.6 cm in diameter *Boulder – more than 25.6 cm in diameter. *Other, assorted organic matter, detritus. Stream substrate can affect the life found within the stream habitat. Muddy streams generally have more sediment in the water, reducing clarity. Clarity is one guide to stream health. Marine substrate can be classified geologically as well. See Green et al ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Salinity
Salinity () is the saltiness or amount of salt (chemistry), salt dissolved in a body of water, called saline water (see also soil salinity). It is usually measured in g/L or g/kg (grams of salt per liter/kilogram of water; the latter is dimensionless and equal to per mille, ‰). Salinity is an important factor in determining many aspects of the chemistry of natural waters and of biological processes within it, and is a state function, thermodynamic state variable that, along with temperature and pressure, governs physical characteristics like the density and heat capacity of the water. A contour line of constant salinity is called an ''isohaline'', or sometimes ''isohale''. Definitions Salinity in rivers, lakes, and the ocean is conceptually simple, but technically challenging to define and measure precisely. Conceptually the salinity is the quantity of dissolved salt content of the water. Salts are compounds like sodium chloride, magnesium sulfate, potassium nitrate, and sod ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plankton
Plankton are the diverse collection of organisms that drift in Hydrosphere, water (or atmosphere, air) but are unable to actively propel themselves against ocean current, currents (or wind). The individual organisms constituting plankton are called plankters. In the ocean, they provide a crucial source of food to many small and large aquatic organisms, such as bivalves, fish, and baleen whales. Marine plankton include bacteria, archaea, algae, protozoa, microscopic fungi, and drifting or floating animals that inhabit the saltwater of oceans and the brackish waters of estuaries. fresh water, Freshwater plankton are similar to marine plankton, but are found in lakes and rivers. Mostly, plankton just drift where currents take them, though some, like jellyfish, swim slowly but not fast enough to generally overcome the influence of currents. Although plankton are usually thought of as inhabiting water, there are also airborne versions that live part of their lives drifting in the at ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
