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Kinorhyncha
Kinorhyncha (, ' "snout") is a phylum of small marine invertebrates that are widespread in mud or sand at all depths as part of the meiobenthos. They are commonly called mud dragons. Modern species are or less, but Cambrian forms could reach . Anatomy Kinorhynchs are limbless animals, with a body consisting of a head, neck, and a trunk of eleven segments. They are the only members of Ecdysozoa, except from the panarthropoda, with a segmented body. Juveniles have eight or nine segments, depending on genus, with the last two or three being added later during growth. A Cambrian species, Eokinorhynchus rarus, had about twice as many segments as present forms. Like other ecdysozoans they do not have external cilia, but instead have a number of spines along the body, plus up to seven circles of spines around the head. These spines are used for locomotion, withdrawing the head and pushing forward, then gripping the substrate with the spines while drawing up the body. The body ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Echinoderes
''Echinoderes'' is a genus of mud dragons first described in 1863.Sørensen, Martin Vinther, et al.An exploration of Echinoderes (Kinorhyncha: Cyclorhagida) in Korean and neighboring waters, with the description of four new species and a redescription of E. tchefouensis Lou, 1934. Zootaxa 3368 (2012): 161-196. It is the largest genus within class Kinorhyncha. It is a highly diverse genus, with member species that inhabit "most marine benthic substrates, on latitudes ranging from the Arctic to the tropics, and from the intertidal zone down to the deep sea." Species on the east coasts of North and South America have been extensively studied by Robert P. Higgins. Species in east Asia have been extensively studied by A. V. Adrianov. Members of ''Echinoderes'' are sexually dimorphic. Globally ''Echinoderes'' are the most diverse, abundant and commonly encountered of all kinorhynch genera. The number of described ''Echinoderes'' species has more than doubled since 2002 and it is sti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chinese Alligator
The Chinese alligator (; ), also known as the Yangtze alligator (), China alligator, or historically the muddy dragon, is a crocodilian endemic to China. It and the American alligator (''A. mississippiensis'') are the only living species in the genus ''Alligator'' of the family Alligatoridae. Dark gray or black in color with a fully armored body, the Chinese alligator grows to in length and weighs as an adult. It brumates in burrows in winter and is nocturnal in summer. Mating occurs in early summer, with females most commonly producing 20–30 eggs, which are smaller than those of any other crocodilian. The species is an opportunistic feeder, primarily eating fish and invertebrates. A vocal species, adults bellow during the mating season and young vocalize to communicate with their parents and other juveniles. Captive specimens have reached age 70, and wild specimens can live past 50. Living in bodies of fresh water, the Chinese alligator's range is restricted to six regions ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phylum (biology)
In biology, a phylum (; : phyla) is a level of classification, or taxonomic rank, that is 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 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 distinguished them as a group ("a self-contained unity"): "perhap ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Invertebrate
Invertebrates are animals that neither develop nor retain a vertebral column (commonly known as a ''spine'' or ''backbone''), which evolved from the notochord. It is a paraphyletic grouping including all animals excluding the chordata, chordate subphylum Vertebrata, i.e. vertebrates. Well-known Phylum, phyla of invertebrates include arthropods, molluscs, annelids, echinoderms, flatworms, cnidarians, and sponges. The majority of animal species are invertebrates; one estimate puts the figure at 97%. Many invertebrate taxon, taxa have a greater number and diversity of species than the entire subphylum of Vertebrata. Invertebrates vary widely in size, from 10 Micrometre, μm (0.0004 in) myxozoans to the 9–10 m (30–33 ft) colossal squid. Some so-called invertebrates, such as the Tunicata and Cephalochordata, are actually sister chordate subphyla to Vertebrata, being more closely related to vertebrates than to other invertebrates. This makes the "invertebrates" para ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Meiobenthos
Meiobenthos, also called meiofauna, are small benthic invertebrates that live in marine or freshwater environments, or both. The term ''meiofauna'' loosely defines a group of organisms by their sizelarger than microfauna but smaller than macrofaunarather than by their taxonomy. This fauna includes both animals that turn into macrofauna later in life, and those small enough to belong to the meiobenthos their entire life. In marine environments there can be thousands of individuals in 10 cubic centimeters of sediment, and counts animals like nematodes, copepods, rotifers, tardigrades and ostracods, but protists like ciliates and foraminifers within the size range of the meiobenthos are also often included. In practice, the term usually includes organisms that can pass through a 1 mm mesh but are retained by a 45 μm mesh, though exact dimensions may vary. Whether an organism will pass through a 1 mm mesh also depends upon whether it is alive or dead at the time o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coelom
The coelom (or celom) is the main body cavity in many animals and is positioned inside the body to surround and contain the digestive tract and other organs. In some animals, it is lined with mesothelium. In other animals, such as molluscs, it remains undifferentiated. In the past, and for practical purposes, coelom characteristics have been used to classify bilaterian animal phyla into informal groups. Etymology The term ''coelom'' derives from the Ancient Greek word () 'cavity'. Structure Development The coelom is the mesodermally lined cavity between the gut and the outer body wall. During the development of the embryo, coelom formation begins in the gastrulation stage. The developing digestive tube of an embryo forms as a blind pouch called the archenteron. In protostomes, the coelom forms by a process known as schizocoely. The archenteron initially forms, and the mesoderm splits into two layers: the first attaches to the body wall or ectoderm, forming ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protonephridium
The nephridium (: nephridia) is an invertebrate organ, found in pairs and performing a function similar to the vertebrate kidneys (which originated from the chordate nephridia). Nephridia remove metabolic wastes from an animal's body. Nephridia come in two basic categories: metanephridia and protonephridia. All nephridia- and kidney- having animals belong to the clade Nephrozoa. Metanephridia A metanephridium (''meta'' = "after") is a type of excretory gland found in many types of invertebrates such as annelids, arthropods and mollusca. (In mollusca, it is known as the Bojanus organ.) A metanephridium typically consists of the nephrostome (a ciliated funnel) opening into the body cavity, connected to a duct which may be variously glandularized, folded or expanded (vesiculate) and which typically opens to the organism's exterior. These ciliated tubules pump water carrying surplus ions, metabolic waste, toxins from food, and useless hormones out of the organism by directing them ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anus
In mammals, invertebrates and most fish, the anus (: anuses or ani; from Latin, 'ring' or 'circle') is the external body orifice at the ''exit'' end of the digestive tract (bowel), i.e. the opposite end from the mouth. Its function is to facilitate the defecation, expulsion of wastes that remain after digestion. Bowel contents that pass through the anus include the gaseous flatus and the semi-solid feces, which (depending on the type of animal) include: indigestible matter such as bones, hair pellet (ornithology), pellets, endozoochory, endozoochorous seeds and gastrolith, digestive rocks; Summary at residual food material after the digestible nutrients have been extracted, for example cellulose or lignin; ingested matter which would be toxic if it remained in the digestive tract; excretion, excreted metabolites like bilirubin-containing bile; and dead mucosal epithelia or excess gut bacteria and other endosymbionts. Passage of feces through the anus is typically controlled by ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Circulatory System
In vertebrates, the circulatory system is a system of organs that includes the heart, blood vessels, and blood which is circulated throughout the body. It includes the cardiovascular system, or vascular system, that consists of the heart and blood vessels (from Greek meaning ''heart'', and Latin meaning ''vessels''). The circulatory system has two divisions, a systemic circulation or circuit, and a pulmonary circulation or circuit. Some sources use the terms ''cardiovascular system'' and ''vascular system'' interchangeably with ''circulatory system''. The network of blood vessels are the great vessels of the heart including large elastic arteries, and large veins; other arteries, smaller arterioles, capillaries that join with venules (small veins), and other veins. The circulatory system is closed in vertebrates, which means that the blood never leaves the network of blood vessels. Many invertebrates such as arthropods have an open circulatory system with a he ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amoebocyte
An amebocyte or amoebocyte () is a motile cell (moving like an amoeba) in the bodies of invertebrates including cnidaria, echinoderms, mollusca, molluscs, tunicates, sponges, and some chelicerata, chelicerates. Moving by pseudopodia, amebocytes can manifest as blood cells or play a similar biological role. In older literature, the term ''amebocyte'' is sometimes used as a synonym of ''phagocyte''. Purpose Similarly to some of the white blood cells of vertebrates, in many species amebocytes are found in the blood or body fluid (e.g. as the blood cells of ''Limulus'', the horseshoe crab) and play a role in the defense of the organism against pathogens. Depending on the species, an amebocyte may also digest and distribute food, dispose of wastes, form skeletal fibers, fight infections, and change into other cell types. Examples In sponges, amebocytes, also known as archaeocytes, are cells found in the mesohyl that can cellular differentiation, transform into any of the anima ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ventral Nerve Cord
The ventral nerve cord is a major structure of the invertebrate central nervous system. It is the functional equivalent of the vertebrate spinal cord. The ventral nerve cord coordinates neural signaling from the brain to the body and vice versa, integrating sensory input and locomotor output. Because arthropods have an open circulatory system, decapitated insects can still walk, groom, and mate — illustrating that the circuitry of the ventral nerve cord is sufficient to perform complex motor programs without brain input. Structure The ventral nerve cord runs down the ventral ("belly", as opposed to back) plane of the organism. It is made of nervous tissue and is connected to the brain. Ventral nerve cord neurons are physically organized into neuromeres that process signals for each body segment. Anterior neuromeres control the anterior body segments, such as the forelegs, and more posterior neuromeres control the posterior body segments, such as the hind legs. Neurom ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
