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Polypodiidae (cnidarians)
''Polypodium'' is a genus of cnidarians that parasitizes in the eggs of sturgeon and similar fishes (Acipenseridae and Polyodontidae). It is one of the few metazoans (animals) that live inside the cells of other animals. ''Polypodium hydriforme'' is the only species of this monotypic genus. The parent family (Polypodiidae), order (Polypodiidea) and class (Polypodiozoa) are also monotypic. Taxonomy Unusual characteristics have led to much controversy regarding the phylogenetic position of ''Polypodium'' within metazoans. ''Polypodium'' has traditionally been considered a cnidarian because it possesses nematocysts, the stinging structures characteristic of this phylum. Molecular phylogenetic studies using 18S rDNA sequence data temporarily challenged this interpretation, by finding that ''Polypodium'' is a close relative to myxozoans and suggesting that together they share a closer affinity to bilaterians than cnidarians. Due to the variable rates of 18S rDNA sequences, thes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phylum
In biology, a phylum (; plural: phyla) is a level of classification or taxonomic rank below kingdom and above class. Traditionally, in botany the term division has been used instead of phylum, although the International Code of Nomenclature for algae, fungi, and plants accepts the terms as equivalent. Depending on definitions, the animal kingdom Animalia contains about 31 phyla, the plant kingdom Plantae contains about 14 phyla, and the fungus kingdom Fungi contains about 8 phyla. Current research in phylogenetics is uncovering the relationships between phyla, which are contained in larger clades, like Ecdysozoa and Embryophyta. General description The term phylum was coined in 1866 by Ernst Haeckel from the Greek (, "race, stock"), related to (, "tribe, clan"). Haeckel noted that species constantly evolved into new species that seemed to retain few consistent features among themselves and therefore few features that distinguished them as a group ("a self-contained unity" ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acipenser
''Acipenser'' is a genus of sturgeons. With 17 living species (others are only known from fossil remains), it is the largest genus in the order Acipenseriformes. The genus is paraphyletic, containing all sturgeons that do not belong to ''Huso'', ''Scaphirhynchus,'' or ''Pseudoscaphirhynchus,'' with many species more closely related to the other three genera than they are to other species of ''Acipenser''. They are native to freshwater and estuarine systems of Eurasia and North America, and most species are threatened. Several species also known to enter near-shore marine environments in the Atlantic, Arctic and Pacific oceans. Living species There are 17 living species: *''Acipenser baerii'' J. F. Brandt, 1869 **'' Acipenser baerii baerii'' J. F. Brandt, 1869 (Siberian sturgeon) **'' Acipenser baerii baicalensis'' A. M. Nikolskii, 1896 (Baikal sturgeon) **''Acipenser baerii stenorrhynchus'' A. M. Nikolskii, 1896 *'' Acipenser brevirostrum'' Lesueur, 1818 (Shortnose sturgeon) ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Russia
Russia (, , ), or the Russian Federation, is a List of transcontinental countries, transcontinental country spanning Eastern Europe and North Asia, Northern Asia. It is the List of countries and dependencies by area, largest country in the world, with its internationally recognised territory covering , and encompassing one-eighth of Earth's inhabitable landmass. Russia extends across Time in Russia, eleven time zones and shares Borders of Russia, land boundaries with fourteen countries, more than List of countries and territories by land borders, any other country but China. It is the List of countries and dependencies by population, world's ninth-most populous country and List of European countries by population, Europe's most populous country, with a population of 146 million people. The country's capital and List of cities and towns in Russia by population, largest city is Moscow, the List of European cities by population within city limits, largest city entirely within E ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Volga
The Volga (; russian: Во́лга, a=Ru-Волга.ogg, p=ˈvoɫɡə) is the List of rivers of Europe#Rivers of Europe by length, longest river in Europe. Situated in Russia, it flows through Central Russia to Southern Russia and into the Caspian Sea. The Volga has a length of , and a catchment area of «Река Волга» , Russian State Water Registry which is more than twice the size of Ukraine. It is also Europe's largest river in terms of average discharge (hydrology), discharge at delta – between and – and of drainage basin. It is widely regarded as the Rivers in Russia, national river of Russia. The hypothetical old Russian state, the Rus' Khaganate, arose along the Volga . Historically, the river served as an important meeting place of various Eurasian civilizations. The river flows in Russia through forests, Fo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sterlet
The sterlet (''Acipenser ruthenus'') is a relatively small species of sturgeon from Eurasia native to large rivers that flow into the Black Sea, Azov Sea, and Caspian Sea, as well as rivers in Siberia as far east as Yenisei. Populations migrating between fresh and salt water (anadromous) have been extirpated.Also known as Sterlet sturgeon. Due to overfishing (for its flesh, caviar, and isinglass), pollution, and dams, the sterlet has declined throughout its native range and is considered vulnerable by the IUCN. Restocking projects are ongoing, and it has been introduced to some regions outside its native range, but the latter have generally not become self-sustaining. Today, the majority of the international trade involves sterlets from aquaculture. Physical appearance *The sterlet may reach 16 kg in weight and 100 to 125 cm in length, rarely exceeding a length of 90 cm. *It is quite variable in coloration, but usually has a yellowish ventral side. *It is dist ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polypodium Hydriforme A
''Polypodium'' is a genus of ferns in the family Polypodiaceae, subfamily Polypodioideae, according to the Pteridophyte Phylogeny Group classification of 2016 (PPG I). The genus is widely distributed throughout the world, with the highest species diversity in the tropics. The name is derived from Ancient Greek ''poly'' (πολύ) "many" + ''podion'' (πόδιον) "little foot", on account of the foot-like appearance of the rhizome and its branches. They are commonly called polypodies or rockcap ferns, but for many species unique vernacular names exist. They are terrestrial or epiphytic ferns, with a creeping, densely hairy or scaly rhizome bearing fronds at intervals along its length. The species differ in size and general appearance and in the character of the fronds, which are evergreen, persisting for 1–2 years, pinnate or pinnatifid (rarely simple entire), and from 10–80 cm or more long. The sori or groups of spore-cases (sporangia) are borne on the back of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Myxozoan
Myxozoa (etymology: Greek: μύξα ''myxa'' "slime" or "mucus" + thematic vowel o + ζῷον ''zoon'' "animal") is a subphylum of aquatic cnidarian animals – all obligate parasites. It contains the smallest animals ever known to have lived. Over 2,180 species have been described and some estimates have suggested at least 30,000 undiscovered species. Many have a two-host lifecycle, involving a fish and an annelid worm or a bryozoan. The average size of a myxosporean spore usually ranges from 10 μm to 20 μm, whereas that of a malacosporean (a subclade of the Myxozoa) spore can be up to 2 mm. Myxozoans can live in both freshwater and marine habitats. Myxozoans are highly derived cnidarians that have undergone dramatic evolution from a free swimming, self-sufficient jellyfish-like creature into their current form of obligate parasites composed of very few cells – sometimes only a single cell. As myxozoans evolved into microscopic parasites, they lost many g ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Taxon
In biology, a taxon (back-formation from ''taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular name and given a particular ranking, especially if and when it is accepted or becomes established. It is very common, however, for taxonomists to remain at odds over what belongs to a taxon and the criteria used for inclusion. If a taxon is given a formal scientific name, its use is then governed by one of the nomenclature codes specifying which scientific name is correct for a particular grouping. Initial attempts at classifying and ordering organisms (plants and animals) were set forth in Carl Linnaeus's Linnaean taxonomy, system in ''Systema Naturae'', 10th edition (1758), as well as an unpublished work by Bernard de Jussieu, Bernard and Antoine Laurent de Jussieu. The idea of a unit-based system of biological classification was first mad ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Science (journal)
''Science'', also widely referred to as ''Science Magazine'', is the peer-reviewed academic journal of the American Association for the Advancement of Science (AAAS) and one of the world's top academic journals. It was first published in 1880, is currently circulated weekly and has a subscriber base of around 130,000. Because institutional subscriptions and online access serve a larger audience, its estimated readership is over 400,000 people. ''Science'' is based in Washington, D.C., United States, with a second office in Cambridge, UK. Contents The major focus of the journal is publishing important original scientific research and research reviews, but ''Science'' also publishes science-related news, opinions on science policy and other matters of interest to scientists and others who are concerned with the wide implications of science and technology. Unlike most scientific journals, which focus on a specific field, ''Science'' and its rival ''Nature (journal), Nature'' c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Long Branch Attraction
In phylogenetics, long branch attraction (LBA) is a form of systematic error whereby distantly related lineages are incorrectly inferred to be closely related. LBA arises when the amount of molecular or morphological change accumulated within a lineage is sufficient to cause that lineage to appear similar (thus closely related) to another long-branched lineage, solely because they have both undergone a large amount of change, rather than because they are related by descent. Such bias is more common when the overall divergence of some taxa results in long branches within a phylogeny. Long branches are often attracted to the base of a phylogenetic tree, because the lineage included to represent an outgroup is often also long-branched. The frequency of true LBA is unclear and often debated, and some authors view it as untestable and therefore irrelevant to empirical phylogenetic inference. Although often viewed as a failing of parsimony-based methodology, LBA could in principle resul ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cladistics (journal)
''Cladistics'' is a bimonthly peer-reviewed scientific journal which has published research in cladistics since 1985. It is published by Wiley-Blackwell on behalf of the Willi Hennig Society. ''Cladistics'' publishes papers relevant to evolution, systematics, and integrative biology. Papers of both a conceptual or philosophical nature, discussions of methodology, empirical studies on taxonomic groups from animals to bacteria, and applications of systematics in disciplines such as genomics, paleontology and biomedical epidemiology are accepted. Five types of paper appear in the journal: reviews, regular papers, forum papers, letters to the editor, and book reviews. According to the ''Journal Citation Reports'', the journal has a 2020 impact factor of 5.254, ranking it 10th out of 50 journals in the category "Evolutionary Biology". Its editor-in-chief An editor-in-chief (EIC), also known as lead editor or chief editor, is a publication's editorial leader who has final responsibi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
