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Protoconch
A protoconch (meaning first or earliest or original shell) is an embryonic or larval shell which occurs in some classes of molluscs, e.g., the initial chamber of an ammonite or the larval shell of a gastropod. In older texts it is also called "nucleus". The protoconch may sometimes consist of several whorls, but when this is the case, the whorls show no growth lines. The whorls of the adult shell, which are formed after the protoconch, are known as the teleoconch. The teleoconch starts forming when the larval gastropod becomes a juvenile, and the protoconch may dissolve. Quite often there is a visible line of demarcation where the protoconch ends and the teleoconch begins, and there may be a noticeable change in sculpture, or a sudden appearance of sculpture at that point. In some gastropod groups (such as the Architectonicidae), the teleoconch whorls spiral in the opposite direction to the protoconch. In those cases, the shell is called heterostrophic. In species which ha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Teleoconch
The gastropod shell is part of the body of a gastropod or snail, a kind of mollusc. The shell is an exoskeleton, which protects from predators, mechanical damage, and dehydration, but also serves for muscle attachment and calcium storage. Some gastropods appear shell-less (slugs) but may have a remnant within the mantle, or in some cases the shell is reduced such that the body cannot be retracted within it (semi-slug). Some snails also possess an operculum that seals the opening of the shell, known as the aperture, which provides further protection. The study of mollusc shells is known as conchology. The biological study of gastropods, and other molluscs in general, is malacology. Shell morphology terms vary by species group. Shell layers The gastropod shell has three major layers secreted by the mantle. The calcareous central layer, tracum, is typically made of calcium carbonate precipitated into an organic matrix known as conchiolin. The outermost layer is the periostra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Whorl (mollusc)
A whorl is a single, complete 360° revolution or turn in the spiral growth of a mollusc shell. A spiral configuration of the shell is found in numerous gastropods, but it is also found in shelled cephalopods including ''Nautilus'', ''Spirula'' and the large extinct subclass of cephalopods known as the ammonites. A spiral shell can be visualized as consisting of a long conical tube, the growth of which is coiled into an overall helical or planispiral shape, for reasons of both strength and compactness. The number of whorls which exist in an adult shell of a particular species depends on mathematical factors in the geometric growth, as described in D'Arcy Wentworth Thompson's classic 1917 book ''On Growth and Form'', and by David Raup. The main factor is how rapidly the conical tube expands (or flares-out) over time. When the rate of expansion is low, such that each subsequent whorl is not that much wider than the previous one, then the adult shell has numerous whorls. When the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Haliotis Asinina Trochophore Protoconch
''Haliotis'', common name abalone, is the only genus in the family Haliotidae. This genus once contained six subgenera. These subgenera have become alternate representations of ''Haliotis''. The genus consists of small to very large, edible, herbivorous sea snails, marine gastropod molluscs. The number of species recognized worldwide ranges between 30 and 130, with over 230 species-level taxa described. The most comprehensive treatment of the family considers 56 species valid, with 18 additional subspecies. Other common names are ear shells, sea ears, and, rarely, muttonfish or muttonshells in parts of Australia, ormer in the UK, perlemoen in South Africa, and the Maori name for three species in New Zealand is pāua. Description The shells of abalones have a low, open, spiral structure, and are characterized by having several open respiratory pores in a row near the shell's outer edge. The thick inner layer of the shell is composed of nacre, which in many species of ab ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Microscope
A microscope () is a laboratory instrument used to examine objects that are too small to be seen by the naked eye. Microscopy is the science of investigating small objects and structures using a microscope. Microscopic means being invisible to the eye unless aided by a microscope. There are many types of microscopes, and they may be grouped in different ways. One way is to describe the method an instrument uses to interact with a sample and produce images, either by sending a beam of light or electrons through a sample in its optical path, by detecting photon emissions from a sample, or by scanning across and a short distance from the surface of a sample using a probe. The most common microscope (and the first to be invented) is the optical microscope, which uses lenses to refract visible light that passed through a thinly sectioned sample to produce an observable image. Other major types of microscopes are the fluorescence microscope, electron microscope (both the transmi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Atlanta Lesueurii 2
Atlanta ( ) is the capital and most populous city of the U.S. state of Georgia. It is the seat of Fulton County, the most populous county in Georgia, but its territory falls in both Fulton and DeKalb counties. With a population of 498,715 living within the city limits, it is the eighth most populous city in the Southeast and 38th most populous city in the United States according to the 2020 U.S. census. It is the core of the much larger Atlanta metropolitan area, which is home to more than 6.1 million people, making it the eighth-largest metropolitan area in the United States. Situated among the foothills of the Appalachian Mountains at an elevation of just over above sea level, it features unique topography that includes rolling hills, lush greenery, and the most dense urban tree coverage of any major city in the United States. Atlanta was originally founded as the terminus of a major state-sponsored railroad, but it soon became the convergence point among several rai ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Atlanta Lesueurii
''Atlanta lesueurii'' is a species of sea snail, a holoplanktonic marine gastropod mollusk in the family Atlantidae. Description The maximal shell size of ''Atlanta lesueurii'' appears to vary geographically (from 2 mm in Hawaiian and eastern Australian waters to 6 mm in the tropical western Pacific). The shell is transparent, thin and fragile, with a smooth surface (lacking raised sculpture). The spire is very small, somewhat elevated and compact, consisting of about 2½ whorls. Spire sutures are deep, with the result that the whorls are somewhat rounded in profile and can easily be distinguished. After metamorphosis the outermost whorl enlarges and inflates rapidly and the keel becomes progressively taller, becoming very tall in large adults and having a truncate leading edge. The keel base and spire sutures are colorless. Main features for the recognition of this species are the protoconch composed of just 2¼-3 convex whorls, separated by an incised suture an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Prodissoconch
A prodissoconch (meaning first or earliest or original shell) is an embryonic or larval shell which is present in the larva of a bivalvia, bivalve mollusk (clams, scallops, oysters, etc.). (The homology (biology), homologous structure in gastropods (snails) is called the protoconch.) The prodissoconch is often but not always smooth, and has no growth lines. It is sometimes still present and visible in the adult shell, if there has been no erosion of the shell in that area. The structure of the prodissoconch has been widely used as a discriminating feature in bivalve systematics. Position Once the larval bivalve settles and becomes a juvenile, the rest of the shell starts to grow. The earliest part of the shell that formed often shows in the adult shell as a protruding area known as the umbo (bivalve), umbo, at the tip of which is the prodissoconch, assuming it has not been eroded or obscured in some other way. Quite often there is a visible line of demarkation where the prodisso ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bivalve
Bivalvia (), in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of marine and freshwater molluscs that have laterally compressed bodies enclosed by a shell consisting of two hinged parts. As a group, bivalves have no head and they lack some usual molluscan organs, like the radula and the odontophore. They include the clams, oysters, cockles, mussels, scallops, and numerous other families that live in saltwater, as well as a number of families that live in freshwater. The majority are filter feeders. The gills have evolved into ctenidia, specialised organs for feeding and breathing. Most bivalves bury themselves in sediment, where they are relatively safe from predation. Others lie on the sea floor or attach themselves to rocks or other hard surfaces. Some bivalves, such as the scallops and file shells, can swim. The shipworms bore into wood, clay, or stone and live inside these substances. The shell of a bivalve is composed of calc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Homology (biology)
In biology, homology is similarity due to shared ancestry between a pair of structures or genes in different taxa. A common example of homologous structures is the forelimbs of vertebrates, where the wings of bats and birds, the arms of primates, the front flippers of whales and the forelegs of four-legged vertebrates like dogs and crocodiles are all derived from the same ancestral tetrapod structure. Evolutionary biology explains homologous structures adapted to different purposes as the result of descent with modification from a common ancestor. The term was first applied to biology in a non-evolutionary context by the anatomist Richard Owen in 1843. Homology was later explained by Charles Darwin's theory of evolution in 1859, but had been observed before this, from Aristotle onwards, and it was explicitly analysed by Pierre Belon in 1555. In developmental biology, organs that developed in the embryo in the same manner and from similar origins, such as from matching p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nudibranch
Nudibranchs () are a group of soft-bodied marine gastropod molluscs which shed their shells after their larval stage. They are noted for their often extraordinary colours and striking forms, and they have been given colourful nicknames to match, such as "clown", "marigold", "splendid", "dancer", "dragon", or "sea rabbit". Currently, about 3,000 valid species of nudibranchs are known.Ocean Portal (2017)A Collage of Nudibranch Colors Smithsonian National Museum of Natural History. Retrieved 17 April 2018. The word "nudibranch" comes from the Latin "naked" and the Ancient Greek () "gills". Nudibranchs are often casually called sea slugs, as they are a family of opistobranchs (sea slugs), within the phylum Mollusca (molluscs), but many sea slugs belong to several taxonomic groups which are not closely related to nudibranchs. A number of these other sea slugs, such as the photosynthetic ''Sacoglossa'' and the colourful Aglajidae, are often confused with nudibranchs. Distribut ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Systematics
Biological systematics is the study of the diversification of living forms, both past and present, and the relationships among living things through time. Relationships are visualized as evolutionary trees (synonyms: cladograms, phylogenetic trees, phylogenies). Phylogenies have two components: branching order (showing group relationships) and branch length (showing amount of evolution). Phylogenetic trees of species and higher taxa are used to study the evolution of traits (e.g., anatomical or molecular characteristics) and the distribution of organisms (biogeography). Systematics, in other words, is used to understand the evolutionary history of life on Earth. The word systematics is derived from the Latin word '' systema,'' which means systematic arrangement of organisms. Carl Linnaeus used 'Systema Naturae' as the title of his book. Branches and applications In the study of biological systematics, researchers use the different branches to further understand the relationshi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Architectonicidae
Architectonicidae, common name the staircase shells or sundials, are a family (biology), family of sea snails, marine (ocean), marine gastropod mollusks in the informal group "Lower Heterobranchia" (= Allogastropoda) of the clade Heterobranchia. The extinct families † Amphitomariidae Bandel, 1994 and † Cassianaxidae Bandel, 1996 belong to the same superfamily. Genera Genera within the family Architectonicidae include: * ''Adelphotectonica'' Bieler, 1987 * ''Aguayodiscus'' Jaume & Borro, 1946 * ''Architectonica'' Peter Friedrich Röding, Röding, 1798 – type genus * ''Awarua (gastropod), Awarua'' Mestayer, 1930Mestayer (1930). ''Trans. New Zealand Inst.'' 61: 145. * ''Basisulcata'' Melone & Taviani, 1985 * †''Calodisculus'' Rehder, 1935 * †''Climacopoma'' Fischer, 1885 * †''Dinaxis'' Dall in Aldrich, 1895 * †''Discotectonica'' Marwick, 1931 * †''Disculus'' Deshayes, 1863 * †''Eosolarium'' Chavan, 1947 * †''Ewekorolaxis'' Adegoke, 1977 * ''Grandeliacus'' Ired ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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