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. St ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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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 Raton, FL.Eise ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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Ascidians
Ascidiacea, commonly known as the ascidians, tunicates (in part), and sea squirts (in part), is a polyphyletic class in the subphylum Tunicata of sac-like marine invertebrate filter feeders. Ascidians are characterized by a tough outer "tunic" made of a polysaccharide. Ascidians are found all over the world, usually in shallow water with salinities over 2.5%. While members of the Thaliacea and Larvacea (Appendicularia) 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 colonies up to several meters in diameter. Sea squirts feed by taking in water through a tube, the oral siphon. The water enters the mouth ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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Alkene
In organic chemistry, an alkene is a hydrocarbon containing a carbon–carbon double bond. Alkene is often used as synonym of olefin, that is, any hydrocarbon containing one or more double bonds.H. Stephen Stoker (2015): General, Organic, and Biological Chemistry'. 1232 pages. Two general types of monoalkenes are distinguished: terminal and internal. Also called α-olefins, terminal alkenes are more useful. However, the International Union of Pure and Applied Chemistry (IUPAC) recommends using the name "alkene" only for 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 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 '' ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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Mollusks
Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is estimated between 60,000 and 100,000 additional species. 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. Numerous molluscs also live in freshwater and terrestrial habitats. They are highly diverse, not just in size and anatomical structure, but also in behaviour and habitat. 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 invertebrate species. The gastropods ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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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, about 500 million years ago. 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 t ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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Hydromedusae
Hydrozoa (hydrozoans; ) are 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 and 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), "air fern" (''Sertularia argentea''), and pink-hearted hydroids (''Tubularia''). Anatomy Most hydrozoan species include both a polypoid and a medusoid stage in their lifecycles, although a number of them have only one or the other. For example, ''Hydra'' has no medusoid stage, while '' Liriope'' lacks the polypoid stage. Polyps The hydroid fo ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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Pycnopodia Helianthoides
''Pycnopodia helianthoides'', commonly known as the sunflower sea star, is a large sea star found in the northeast Pacific. 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; their color can vary widely. They are predatory, feeding mostly on sea urchins, clams, snails, and other small invertebrates. Although the species had been widely distributed throughout the northeast Pacific, its population has rapidly declined since 2013. The sea star has been on IUCN list of endangered animals since 2021. Description Sunflower sea stars can grow to have an arm span of in diameter. They are the second-biggest sea star in the world, only second to the poorly known deep water '' Midgardia xandaros'', whose arm span is and its body is 2.6 cm (roughly 1 inch) wide, although ''P. helianthoides'' is the largest known echinoderm by mass. Growth of the sea star b ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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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 herb ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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Sepia Officinalis {{redirect category shell, {{R from other capitalisation{{R from move ...
#REDIRECT Common cuttlefish #REDIRECT Common cuttlefish #REDIRECT Common cuttlefish {{redirect category shell, {{R from other capitalisation{{R from move ... {{redirect category shell, {{R from other capitalisation{{R from move ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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Pteridium Aquilinum
''Pteridium aquilinum'' (bracken, brake or common bracken), 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. Etymology Common bracken was first described as ''Pteris aquilina'' by Carl Linnaeus, in Volume 2 of his ''Species Plantarum'' in 1753. The origin of the specific epithet derived from the Latin ''aquila'' "eagle". In the reprint of the ''Flora Suecica'' in 1755, Linnaeus explains that the name refers to the image of an eagle seen in the transverse section of the root. In spite of this, the opinion has been forwarded that the name pertains to the shape of the mature fronds appearing akin to an eagle's wing. However, medieval scholars, including Erasmus, thought the pattern of the fibres seen in a transverse section of the stipe resembled a double-headed eagle or oak tree. Ta ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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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 ''Montipo ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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Ciona
''Ciona'' is a genus of tunicate, sea squirts in the family Cionidae. The body of ''Ciona'' is bag-like and covered by a tunica (biology), tunic, which is a secretion of the Squamous epithelium, epidermal cells. The body is attached at a permanent base located at the posterior part, and the opposite bears two openings, the Cheek, buccal (Mouth, oral) and atrial (cloacal) siphon (mollusc), siphons. The water is drawn into the ascidian through the buccal siphon and leaves the wikt:atrium, 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.: ''T ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |