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Nereididae
Nereididae (formerly spelled Nereidae) are a family of polychaete worms. It contains about 500 – mostly marine – species grouped into 42 genera. They may be commonly called ragworms or clam worms. Characteristics The prostomium of Nereididae bears a pair of palps that are differentiated into two units, the proximal unit is much larger than the distal unit. Parapodia are mostly biramous (only the first two pairs are uniramous). Peristomium fused with the first body segment, with usually two pairs of tentacular cirri. The first body segment with 1-2 pairs tentacular cirri without aciculae. Compound setae present. Notopodia are distinct (rarely reduced), usually with more flattened lobes, notosetae compound falcigers and/or spinigers (rarely notosetae absent). They have two prostomial antennae (absent in ''Micronereis''). Their pharynx, when everted, clearly consists of two portions, with a pair of strong jaws on the distal portion and usually with conical teeth ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polychaeta
Polychaeta () is a paraphyletic class of generally marine annelid worms, commonly called bristle worms or polychaetes (). Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called chaetae, which are made of chitin. More than 10,000 species are described in this class. Common representatives include the lugworm (''Arenicola marina'') and the sandworm or clam worm ''Alitta''. Polychaetes as a class are robust and widespread, with species that live in the coldest ocean temperatures of the abyssal plain, to forms which tolerate the extremely high temperatures near hydrothermal vents. Polychaetes occur throughout the Earth's oceans at all depths, from forms that live as plankton near the surface, to a 2- to 3-cm specimen (still unclassified) observed by the robot ocean probe ''Nereus'' at the bottom of the Challenger Deep, the deepest known spot in the Earth's oceans. Only 168 species (less than 2% of all polychaetes) are known fro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ceratonereis
''Ceratonereis'' is a genus of polychaete worms from the family Nereididae. Species The following species are assigned to ''Ceratonereis'': * ''Ceratonereis brunnea'' Langerhans, 1884 * ''Ceratonereis dawydovi'' ( Fauvel, 1937) * ''Ceratonereis debilis'' ( Grube, 1857) * ''Ceratonereis divaricata'' (Grube, 1878) * ''Ceratonereis dorsolineata'' (Horst, 1924) * ''Ceratonereis fallax'' ( Quatrefages, 1866) * ''Ceratonereis gracilis'' (Webster Webster may refer to: People *Webster (surname), including a list of people with the surname *Webster (given name), including a list of people with the given name Places Canada *Webster, Alberta * Webster's Falls, Hamilton, Ontario United Stat ..., 1884) * ''Ceratonereis hastifera'' (Fauvel, 1937) * ''Ceratonereis hemphrichii'' (Grube, 1873) * ''Ceratonereis imperfecta'' ( Gravier & Dantan, 1934) * ''Ceratonereis incisa'' (Gravier & Dantan, 1934) * ''Ceratonereis japonica'' Imajima, 1972 * ''Ceratonereis kardagica'' (Vinogradov, 1933) * ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ceratocephale
''Ceratocephale'' is a genus of polychaetes belonging to the family Nereididae. The species of this genus inhabit marine and brackish Brackish water, sometimes termed brack water, is water occurring in a natural environment that has more salinity than freshwater, but not as much as seawater. It may result from mixing seawater (salt water) and fresh water together, as in estu ... environments. Species Species in this genus include: * '' Ceratocephale abyssorum'' (Hartman & Fauchald, 1971) * '' Ceratocephale andaman'' Hylleberg & Natewathana, 1988 References Polychaetes {{Annelid-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alitta
''Alitta'' is a genus of marine annelids in Nereididae family (commonly known as sandworms or ragworms). There are three recognised species within the genus, ''Alitta grandis'' (Stimpson, 1853), '' Alitta succinea'' (Frey & Leuckart, 1847) and '' Alitta virens'' (M. Sars, 1835).Fauchald, K.; Glasby, C. (2009)Alitta Bakken & Wilson, 2005 Fauchald, K. (Ed) (2009). World Polychaeta database. Accessed through the World Register of Marine Species on 2 August 2010 ''Alitta brandti'' Malmgren, 1865 was originally considered part of the genus, but is now accepted as ''Neanthes brandti Neanthes may refer to: * ''Neanthes'' (polychaete), a genus of polychaetes in the family Nereididae * ''Neanthes'', a genus of beetles in the family Cerambycidae; synonym of '' Acalolepta'' * Neanthes of Cyzicus Neanthes of Cyzicus (; el, Νεάν ...'' (Malmgren, 1865). References Phyllodocida Polychaete genera {{annelid-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hesionidae
Hesionidae are a family of phyllodocid "bristle worms" (class Polychaeta). They are (like almost all polychaetes) marine organisms. Most are found on the continental shelf; '' Hesiocaeca methanicola'' is found on methane ice, where it feeds on bacterial biofilms. A characteristic apomorphy of the Hesionidae are the cirrophores of the anterior segments, which are well-developed cup-like sheaths; the cirri of the subsequent segments insert into the parapodia directly, or with just a vestigial cirrophore. Systematics As phyllodocids, the Hesionidae belong to the order Aciculata, one of the three main clades of polychaetes. They appear to be part of the basal radiation of the main lineage of phyllodocids, alongside such families as the ragworms (Nereididae), the Pilargidae and Sphaerodoridae which are closely related to each other, the very ancient Syllidae, and perhaps the more advanced catworms (Nephtyidae). Numerous genera are still treated as Hesionidae ''in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bone
A bone is a rigid organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red and white blood cells, store minerals, provide structure and support for the body, and enable mobility. Bones come in a variety of shapes and sizes and have complex internal and external structures. They are lightweight yet strong and hard and serve multiple functions. Bone tissue (osseous tissue), which is also called bone in the uncountable sense of that word, is hard tissue, a type of specialized connective tissue. It has a honeycomb-like matrix internally, which helps to give the bone rigidity. Bone tissue is made up of different types of bone cells. Osteoblasts and osteocytes are involved in the formation and mineralization of bone; osteoclasts are involved in the resorption of bone tissue. Modified (flattened) osteoblasts become the lining cells that form a protective layer on the bone surface. The mineralize ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phylogenetic Tree
A phylogenetic tree (also phylogeny or evolutionary tree Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA.) is a branching diagram or a tree showing the evolutionary relationships among various biological species or other entities based upon similarities and differences in their physical or genetic characteristics. All life on Earth is part of a single phylogenetic tree, indicating common ancestry. In a ''rooted'' phylogenetic tree, each node with descendants represents the inferred most recent common ancestor of those descendants, and the edge lengths in some trees may be interpreted as time estimates. Each node is called a taxonomic unit. Internal nodes are generally called hypothetical taxonomic units, as they cannot be directly observed. Trees are useful in fields of biology such as bioinformatics, systematics, and phylogenetics. ''Unrooted'' trees illustrate only the relatedness of the leaf nodes and do not require the ancestral root to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Monophyletic
In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic groups are typically characterised by shared derived characteristics ( synapomorphies), which distinguish organisms in the clade from other organisms. An equivalent term is holophyly. The word "mono-phyly" means "one-tribe" in Greek. Monophyly is contrasted with paraphyly and polyphyly as shown in the second diagram. A ''paraphyletic group'' consists of all of the descendants of a common ancestor minus one or more monophyletic groups. A '' polyphyletic group'' is characterized by convergent features or habits of scientific interest (for example, night-active primates, fruit trees, aquatic insects). The features by which a polyphyletic group is differentiated from others are not inherited from a common ancestor. These definitions have ta ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zinc
Zinc is a chemical element with the symbol Zn and atomic number 30. Zinc is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodic table. In some respects, zinc is chemically similar to magnesium: both elements exhibit only one normal oxidation state (+2), and the Zn2+ and Mg2+ ions are of similar size.The elements are from different metal groups. See periodic table. Zinc is the 24th most abundant element in Earth's crust and has five stable isotopes. The most common zinc ore is sphalerite (zinc blende), a zinc sulfide mineral. The largest workable lodes are in Australia, Asia, and the United States. Zinc is refined by froth flotation of the ore, roasting, and final extraction using electricity ( electrowinning). Zinc is an essential trace element for humans, animals, plants and for microorganisms and is necessary for prenatal and postnatal development. It ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
