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Nematomorpha
Nematomorpha (sometimes called Gordiacea, and commonly known as horsehair worms, hairsnakes, or Gordian worms) are a phylum of parasitoid animals superficially similar to nematode worms in morphology, hence the name. Most species range in size from , reaching in extreme cases, and in diameter. Horsehair worms can be discovered in damp areas, such as watering troughs, swimming pools, streams, puddles, and cisterns. The adult worms are free-living, but the larvae are parasitic on arthropods, such as beetles, cockroaches, mantises, orthopterans, and crustaceans. About 351 freshwater species are known and a conservative estimate suggests that there may be about 2000 freshwater species worldwide. The name "Gordian" stems from the legendary Gordian knot. This relates to the fact that nematomorphs often coil themselves in tight balls that resemble knots. Description and biology Nematomorphs possess an external cuticle without cilia. Internally, they have only longitudinal muscle and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nectonematoidea
''Nectonema'' is a genus of marine Nematomorpha, horsehair worms first described by Addison Emery Verrill, Addison E. Verrill in 1879. It is the only genus in the family Nectonematidae described by Henry Baldwin Ward, Henry B. Ward in 1892, in the order Nectonematoidea, and in the class Nectonematoida. The genus contains five species; all species have a Parasitism, parasitic Larva, larval stage inhabiting crustacean hosts and a free-living adult stage that swims in open water. Taxonomy Nectonematoidea is one of two orders within the phylum Nematomorpha, the other being Gordioidea. The latter is likewise in a single class Gordioida, which is a significantly larger taxon, with over 300 known species. Nematomorpha are known as horsehair worms or Gordian worms, and form a sister-group to the nematodes. The following classification shows the place of Nectonematoida within the protostomes according to Minelli (2008) and Tedersoo (2017): Within Nectonematoida only a single genus, ''Ne ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nematode
The nematodes ( or ; ; ), roundworms or eelworms constitute the phylum Nematoda. Species in the phylum inhabit a broad range of environments. Most species are free-living, feeding on microorganisms, but many are parasitic. Parasitic worms (helminths) are the cause of soil-transmitted helminthiases. They are classified along with arthropods, tardigrades and other moulting animals in the clade Ecdysozoa. Unlike the flatworms, nematodes have a tubular digestive system, with openings at both ends. Like tardigrades, they have a reduced number of Hox genes, but their sister phylum Nematomorpha has kept the ancestral protostome Hox genotype, which shows that the reduction has occurred within the nematode phylum. Nematode species can be difficult to distinguish from one another. Consequently, estimates of the number of nematode species are uncertain. A 2013 survey of animal biodiversity suggested there are over 25,000. Estimates of the total number of extant species are su ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gordioidea
Gordioidea is an order (biology), order (sometimes placed at superfamily level) of parasitic Nematomorpha, horsehair worms. Its taxonomy remains uncertain, but appears to be contained in the monotypic class Gordioida and contains about 320 known species. Biology Gordioidean adults are free-living in freshwater or semi-terrestrial habitats and larvae parasitise insects, primarily Orthopterans. Unlike Nectonematoideans, which are marine, gordioideans lack lateral rows of setae and have a single, ventral epidermal cord and their blastocoel is filled with mesenchyme in young worms but become open when older.Pechenik (2010) ''Biology of the Invertebrates'', p. 457. Families and genera The Integrated Taxonomic Information System lists the following genera in two families: Chordodidae Auth. May, 1919; selected genera: ;Subfamily Chordodinae Heinze, 1935 * ''Chordodes'' Creplin, 1847 * ''Dacochordodes'' Capuse, 1965 * ''Euchordodes'' Heinze, 1937 * ''Neochordodes'' Carvalho, 1942 * '' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paragordius Tricuspidatus
''Paragordius tricuspidatus'' is a species of parasitic worm that affects the cricket ''Nemobius sylvestris''. In its larval stage, the worm is microscopic, but grows into a large worm () inside its host after accidental ingestion since their eggs are laid at the edge of the water by rivers where crickets frequently reside. Upon ingestion, the worm nourishes upon its host and fills the entire body cavity of the cricket, until maturation, when the parasitic worm is ready to exit into water to complete its life cycle, maximizing its reproductive success. The worm induces a peculiar behavior in its cricket host which causes the cricket to leap into water whereby the parasitic worm can slither out and find its mate, while the cricket often perishes. Should the cricket be preyed upon by a predator, such as a fish or frog, the worm has the ability to not only escape from the host's body but also the predator's digestive system. The worm emerges from the predator unharmed and proceeds to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arthropod
Arthropods ( ) are invertebrates in the phylum Arthropoda. They possess an arthropod exoskeleton, exoskeleton with a cuticle made of chitin, often Mineralization (biology), mineralised with calcium carbonate, a body with differentiated (Metamerism (biology), metameric) Segmentation (biology), segments, and paired jointed appendages. In order to keep growing, they must go through stages of moulting, a process by which they shed their exoskeleton to reveal a new one. They form an extremely diverse group of up to ten million species. Haemolymph is the analogue of blood for most arthropods. An arthropod has an open circulatory system, with a body cavity called a haemocoel through which haemolymph circulates to the interior Organ (anatomy), organs. Like their exteriors, the internal organs of arthropods are generally built of repeated segments. They have ladder-like nervous systems, with paired Anatomical terms of location#Dorsal and ventral, ventral Ventral nerve cord, nerve cord ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phylum
In biology, a phylum (; : phyla) is a level of classification, or taxonomic rank, that is below Kingdom (biology), kingdom and above Class (biology), class. Traditionally, in botany the term division (taxonomy), 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 eight phyla. Current research in phylogenetics is uncovering the relationships among phyla within 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 distinguishe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parasitoid
In evolutionary ecology, a parasitoid is an organism that lives in close association with its host (biology), host at the host's expense, eventually resulting in the death of the host. Parasitoidism is one of six major evolutionarily stable strategy, evolutionary strategies within parasitism, distinguished by the fatal prognosis for the host, which makes the strategy close to predation. Among parasitoids, strategies range from living inside the host (''endoparasitism''), allowing it to continue growing before emerging as an adult, to Paralysis, paralysing the host and living outside it (''ectoparasitism''). Hosts can include other parasitoids, resulting in hyperparasitism; in the case of oak galls, up to five levels of parasitism are possible. Some parasitoids Behavior-altering parasite, influence their host's behaviour in ways that favour the propagation of the parasitoid. Parasitoids are found in a variety of Taxon, taxa across the insect superorder Endopterygota, whose compl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Larva
A larva (; : larvae ) is a distinct juvenile form many animals undergo before metamorphosis into their next life stage. Animals with indirect development such as insects, some arachnids, amphibians, or cnidarians typically have a larval phase of their life cycle. A larva's appearance is generally very different from the adult form (''e.g.'' caterpillars and butterflies) including different unique structures and organs that do not occur in the adult form. Their diet may also be considerably different. In the case of smaller primitive arachnids, the larval stage differs by having three instead of four pairs of legs. Larvae are frequently adapted to different environments than adults. For example, some larvae such as tadpoles live almost exclusively in aquatic environments but can live outside water as adult frogs. By living in a distinct environment, larvae may be given shelter from predators and reduce competition for resources with the adult population. Animals in the lar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parasite
Parasitism is a Symbiosis, close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the Host (biology), host, causing it some harm, and is Adaptation, adapted structurally to this way of life. The entomologist E. O. Wilson characterised parasites' way of feeding as "predators that eat prey in units of less than one". Parasites include single-celled protozoans such as the agents of malaria, sleeping sickness, and amoebic dysentery; animals such as hookworms, lice, mosquitoes, and vampire bats; fungi such as Armillaria mellea, honey fungus and the agents of ringworm; and plants such as mistletoe, dodder, and the Orobanchaceae, broomrapes. There are six major parasitic Behavioral ecology#Evolutionarily stable strategy, strategies of exploitation of animal hosts, namely parasitic castration, directly transmitted parasitism (by contact), wikt:trophic, trophicallytransmitted parasitism (by being eaten), ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Atdabanian
Cambrian Stage 3 is the still unnamed third stage of the Cambrian. It succeeds Cambrian Stage 2 and precedes Cambrian Stage 4, although neither its base nor top have been formally defined. The plan is for its lower boundary to correspond approximately to the first appearance of trilobites, about million years ago, though the globally asynchronous appearance of trilobites warrants the use of a separate, globally synchronous marker to define the base. The upper boundary and beginning of Cambrian Stage 4 is informally defined as the first appearance of the trilobite genera '' Olenellus'' or '' Redlichia'' around million years ago. Naming The International Commission on Stratigraphy has not officially named the 3rd stage of the Cambrian. The stage approximately corresponds to the "Atdabanian", which is used by geologists working in Siberia. Biostratigraphy The oldest trilobite known is '' Lemdadella'' which appears at the beginning of the '' Fallotaspis'' zone. The Cambrian radi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cuticle
A cuticle (), or cuticula, is any of a variety of tough but flexible, non-mineral outer coverings of an organism, or parts of an organism, that provide protection. Various types of "cuticle" are non- homologous, differing in their origin, structure, function, and chemical composition. Human anatomy In human anatomy, "cuticle" can refer to several structures, but it is used in general parlance, and even by medical professionals, to refer to the thickened layer of skin surrounding fingernails and toenails (the eponychium), and to refer to the superficial layer of overlapping cells covering the hair shaft ( cuticula pili), consisting of dead cells, that locks the hair into its follicle. It can also be used as a synonym for the epidermis, the outer layer of skin. Cuticle of invertebrates In zoology, the invertebrate cuticle or cuticula is a multi-layered structure outside the epidermis of many invertebrates, notably arthropods and roundworms, in which it forms an exoskeleton ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cilia
The cilium (: cilia; ; in Medieval Latin and in anatomy, ''cilium'') is a short hair-like membrane protrusion from many types of eukaryotic cell. (Cilia are absent in bacteria and archaea.) The cilium has the shape of a slender threadlike projection that extends from the surface of the much larger cell body. Eukaryotic flagella found on sperm cells and many protozoans have a similar structure to motile cilia that enables swimming through liquids; they are longer than cilia and have a different undulating motion. There are two major classes of cilia: ''motile'' and ''non-motile'' cilia, each with two subtypes, giving four types in all. A cell will typically have one primary cilium or many motile cilia. The structure of the cilium core, called the axoneme, determines the cilium class. Most motile cilia have a central pair of single microtubules surrounded by nine pairs of double microtubules called a 9+2 axoneme. Most non-motile cilia have a 9+0 axoneme that lacks the central pai ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
