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Sperm Chemotaxis
Sperm chemotaxis is a form of sperm guidance, in which sperm cells (spermatozoa) follow a concentration gradient of a chemoattractant secreted from the oocyte and thereby reach the oocyte. Background Since the discovery of sperm attraction to the female gametes in ferns over a century ago, sperm guidance in the form of sperm chemotaxis has been established in a large variety of speciesMiller, R.L. (1985) ''Sperm chemo-orientation in the metazoa''. In: ''Biology of Fertilization'' (Metz, C.B. and Monroy, A., eds.), pp. 275–337. Academic Press, New York. Although sperm chemotaxis is prevalent throughout the Metazoa kingdom, from marine species with external fertilization such as sea urchins and corals, to humans,Cosson, M.P. (1990) ''Sperm chemotaxis''. In: ''Controls of Sperm Motility: Biological and Clinical Aspects'' (Gagnon, C., ed.) pp. 103–135. CRC Press, Boca Raton, FL.Eisenbach, M. and Tur-Kaspa, I. (1994) ''Human sperm chemotaxis is not enigmatic anymore''. Fertil. Steri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sperm Guidance
Sperm guidance is the process by which sperm cells ( spermatozoa) are directed to the oocyte (egg) for the aim of fertilization. In the case of marine invertebrates the guidance is done by chemotaxis. In the case of mammals, it appears to be done by chemotaxis, thermotaxis and rheotaxis. Background Since the discovery of sperm attraction to the female gametes in ferns over a century ago, sperm guidance in the form of sperm chemotaxis has been established in a large variety of speciesMiller, R.L. (1985) ''Sperm chemo-orientation in the metazoa''. In: ''Biology of Fertilization'' (Metz, C.B. and Monroy, A., eds.), pp. 275–337. Academic Press, New York. Although sperm chemotaxis is prevalent throughout the Metazoa kingdom, from marine species with external fertilization such as sea urchins and corals, to humans,Cosson, M.P. (1990) ''Sperm chemotaxis''. In: ''Controls of Sperm Motility: Biological and Clinical Aspects'' (Gagnon, C., ed.) pp. 103–135. CRC Press, Boca Rato ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ascidians
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 ph ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alkene
In organic chemistry, an alkene, or olefin, is a hydrocarbon containing a carbon–carbon double bond. The double bond may be internal or at the terminal position. Terminal alkenes are also known as Alpha-olefin, α-olefins. The International Union of Pure and Applied Chemistry (IUPAC) Preferred IUPAC name, recommends using the name "alkene" only for Open-chain compound, acyclic hydrocarbons with just one double bond; alkadiene, alkatriene, etc., or polyene for acyclic hydrocarbons with two or more double bonds; cycloalkene, cycloalkadiene, etc. for Cyclic compound, cyclic ones; and "olefin" for the general class – cyclic or acyclic, with one or more double bonds. Acyclic alkenes, with only one double bond and no other functional groups (also known as mono-enes) form a homologous series of hydrocarbons with the general formula with ''n'' being a >1 natural number (which is two hydrogens less than the corresponding alkane). When ''n'' is four or more, isomers are possible, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mollusks
Mollusca is a phylum of protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant species of molluscs are recognized, making it the second-largest animal phylum after Arthropoda. The number of additional fossil species is estimated between 60,000 and 100,000, and the proportion of undescribed species is very high. Many taxa remain poorly studied. Molluscs are the largest marine phylum, comprising about 23% of all the named marine organisms. They are highly diverse, not just in size and anatomical structure, but also in behaviour and habitat, as numerous groups are freshwater and even terrestrial species. The phylum is typically divided into 7 or 8 taxonomic classes, of which two are entirely extinct. Cephalopod molluscs, such as squid, cuttlefish, and octopuses, are among the most neurologically advanced of all invertebrates—and either the giant squid or the colossal squid is the largest known extant invertebrat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ophiuroids
Brittle stars, serpent stars, or ophiuroids (; ; referring to the serpent-like arms of the brittle star) are echinoderms in the class Ophiuroidea, closely related to starfish. They crawl across the sea floor using their flexible arms for locomotion. The ophiuroids generally have five long, slender, whip-like arms which may reach up to in length on the largest specimens. The Ophiuroidea contain two large clades, Ophiurida (brittle stars) and Euryalida (basket stars). Over 2,000 species of brittle stars live today. More than 1,200 of these species are found in deep waters, greater than 200 m deep. Range The ophiuroids diverged in the Early Ordovician. Ophiuroids can be found today in all of the major marine provinces, from the poles to the tropics. Basket stars are usually confined to the deeper parts of this range; Ophiuroids are known even from abyssal (>6,000 m) depths. However, brittle stars are also common members of reef communities, where they hide under rocks and even w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydromedusae
Hydrozoa (hydrozoans; from Ancient Greek ('; "water") and ('; "animals")) is a taxonomic class of individually very small, predatory animals, some solitary and some colonial, most of which inhabit saline water. The colonies of the colonial species can be large, and in some cases the specialized individual animals cannot survive outside the colony. A few genera within this class live in freshwater habitats. Hydrozoans are related to jellyfish and corals, which also belong to the phylum Cnidaria. Some examples of hydrozoans are the freshwater jelly (''Craspedacusta sowerbyi''), freshwater polyps ('' Hydra''), ''Obelia'', Portuguese man o' war (''Physalia physalis''), chondrophores (Porpitidae), and pink-hearted hydroids (''Tubularia''). Anatomy Most hydrozoan species include both a polypoid and a medusoid stage in their life cycles, although a number of them have only one or the other. For example, ''Hydra'' has no medusoid stage, while '' Liriope'' lacks the polypoid stage. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pycnopodia Helianthoides
''Pycnopodia helianthoides'', commonly known as the sunflower sea star, is a large starfish, sea star found in the northeastern Pacific Ocean. The only species of its genus, it is among the largest sea stars in the world, with a maximum arm span of . Adult sunflower sea stars usually have 16 to 24 limbs. They vary in color. Sunflower sea stars are predatory and carnivorous, feeding mostly on sea urchins, clams, sea snails, and other small invertebrates. Although the species was widely distributed throughout the northeast Pacific, its population rapidly declined from 2013. The sunflower sea star is classified as Critically Endangered on the International Union for Conservation of Nature, IUCN IUCN Red List, Red List. Description Sunflower sea stars can reach an arm span of . They are the heaviest known sea star, weighing about 5 kg. They are the second-biggest sea star in the world, second only to the little known deep water ''Midgardia xandaros'', whose arm span is and w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arbacia Punctulata
The Atlantic purple sea urchin (''Arbacia punctulata'') is a species of sea urchins from the family Arbaciidae, native to the Atlantic Ocean. Description The Atlantic purple sea urchin is a spherical, dark purple-spined sea urchin, with a nearly flat oral face. It can reach up to 8 cm in diameter, and is native to the North Atlantic Ocean. Image:Arbacia punctulata 1.jpg, Face – aboral Image:Arbacia punctulata oral face.jpg, Face – oral Habitat and range Its natural habitat is in the western Atlantic Ocean. ''A. punctulata'' can be found in shallow water from Massachusetts to Cuba and the Yucatan Peninsula, from Texas to Florida in the Gulf of Mexico, the coast from Panama to French Guiana, and in the Lesser Antilles, usually on rocky, sandy, or shelly bottoms. Ecology and behaviour ''A. punctulata'' is omnivorous, consuming a wide variety of prey although Karlson classified it as a generalized carnivore. Its galactolipids, rather than phlorotannins, act as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sepia Officinalis
The common cuttlefish or European common cuttlefish (''Sepia officinalis'') is one of the largest and best-known cuttlefish species. They are a migratory species that spend the summer and spring inshore for spawning and then move to depths of during autumn and winter. They grow to in mantle (mollusc), mantle length and in weight. Animals from subtropical seas are smaller and rarely exceed in mantle length. The common cuttlefish is native to at least the Mediterranean Sea, North Sea, and Baltic Sea, although subspecies have been proposed as far south as South Africa. It lives on sand and mud seabeds and it can tolerate brackish water conditions. Taxonomy It is unknown where the type specimen of ''S. officinalis'' was collected, as the location is given simply as "Oceano". It is deposited in the Linnean Society of London. ''Sepia officinalis jurujubai'' Oliveira, 1940, originally described as a subspecies of the common cuttlefish, is a junior synonym of ''Sepioteuthis sepioid ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pteridium Aquilinum
''Pteridium aquilinum'', commonly called bracken, brake, pasture brake, common bracken, and also known as eagle fern, is a species of fern occurring in temperate and subtropical regions in both hemispheres. Originally native to Eurasia and North America, the extreme lightness of its spores has led to it achieving a cosmopolitan distribution. Description Common bracken is a herbaceous perennial plant, deciduous in winter. The large, roughly triangular fronds are produced singly, arising upwards from an underground rhizome, and grow to tall; the main stem, or stipe, is up to in diameter at the base. It dies back to ground level in autumn. The rhizome grows up to deep, about in diameter, and up to long. Because it regrows in the spring from an underground rhizome, ''P. aquilinum'' tends to be found in dense colonies of genetically identical fronds. Such colonies can be as much as 650 years of age, with individual rhizomes living up to 72 years. One colony at Raakkyla, North Ka ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Montipora
''Montipora'' is a genus of Scleractinian corals in the phylum Cnidaria. Members of the genus ''Montipora'' may exhibit many different growth morphologies. With eighty five known species, ''Montipora'' is the second most species rich coral genus after ''Acropora''. Description Growth morphologies for the genus ''Montipora'' include submassive, laminar, foliaceous, encrusting, and branching. It is not uncommon for a single ''Montipora'' colony to display more than one growth morphology. Healthy ''Montipora'' corals can be a variety of colors, including orange, brown, pink, green, blue, purple, yellow, grey, or tan. Although they are typically uniform in color, some species, such as ''Montipora spumosa'' or ''Montipora verrucosa'', may display a mottled appearance. ''Montipora'' corals have the smallest corallites of any coral family. Columellae are not present. Coenosteum and corallite walls are porous, which can result in elaborate structures. The coenosteum of each ''Montipora ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ciona
''Ciona'' is a genus of sea squirts in the family Cionidae. The body of ''Ciona'' is bag-like and covered by a tunic, which is a secretion of the epidermal cells. The body is attached at a permanent base located at the posterior part, and the opposite bears two openings, the buccal (oral) and atrial (cloacal) siphons. The water is drawn into the ascidian through the buccal siphon and leaves the atrium through the atrial siphon. Species Species in this genus include: * '' Ciona antarctica'' * ''Ciona edwardsi'' * ''Ciona fascicularis'' * '' Ciona gelatinosa'' * ''Ciona hoshinoi'' * ''Ciona imperfecta'' * '' Ciona intermedia'' * ''Ciona intestinalis'' * ''Ciona longissima'' * ''Ciona mollis'' * ''Ciona pomponiae'' * ''Ciona robusta'' * ''Ciona roulei'' * ''Ciona savignyi'' * ''Ciona sheikoi'' Genome projects As of 2008, the genomes of ''Ciona intestinalis''P. Dehal et al.: ''The draft genome of Ciona intestinalis: insights into chordate and vertebrate origins.'' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
