Aquaculture known as aquafarming, is the farming of fish, molluscs, aquatic plants and other organisms. Aquaculture involves cultivating freshwater and saltwater populations under controlled conditions, can be contrasted with commercial fishing, the harvesting of wild fish. Mariculture refers to aquaculture practiced in underwater habitats. According to the Food and Agriculture Organization, aquaculture "is understood to mean the farming of aquatic organisms including fish, molluscs and aquatic plants. Farming implies some form of intervention in the rearing process to enhance production, such as regular stocking, protection from predators, etc. Farming implies individual or corporate ownership of the stock being cultivated." The reported output from global aquaculture operations in 2014 supplied over one half of the fish and shellfish, directly consumed by humans. Further, in current aquaculture practice, products from several pounds of wild fish are used to produce one pound of a piscivorous fish like salmon.
Particular kinds of aquaculture include fish farming, shrimp farming, oyster farming, mariculture and the cultivation of ornamental fish. Particular methods include aquaponics and integrated multi-trophic aquaculture, both of which integrate fish farming and aquatic plant farming; the indigenous Gunditjmara people in Victoria, may have raised eels as early as 6000 BC. Evidence indicates they developed about 100 km2 of volcanic floodplains in the vicinity of Lake Condah into a complex of channels and dams, used woven traps to capture eels, preserve them to eat all year round. Aquaculture was operating in China circa 2000 BC; when the waters subsided after river floods, some fish carp, were trapped in lakes. Early aquaculturists fed their brood using nymphs and silkworm feces, ate them. A fortunate genetic mutation of carp led to the emergence of goldfish during the Tang dynasty. However, ancient Egyptians might have farmed fish from Lake Bardawil about 3,500 years ago, they traded them with Canaan.
Gim cultivation is the oldest aquaculture in Korea. Early cultivation methods used bamboo or oak sticks, which were replaced by newer methods that utilized nets in the 19th century. Floating rafts have been used for mass production since the 1920s. Japanese cultivated seaweed by providing bamboo poles and nets and oyster shells to serve as anchoring surfaces for spores. Romans bred fish in ponds and farmed oysters in coastal lagoons before 100 CE. In central Europe, early Christian monasteries adopted Roman aquacultural practices. Aquaculture spread in Europe during the Middle Ages since away from the seacoasts and the big rivers, fish had to be salted so they did not rot. Improvements in transportation during the 19th century made fresh fish available and inexpensive in inland areas, making aquaculture less popular; the 15th-century fishponds of the Trebon Basin in the Czech Republic are maintained as a UNESCO World Heritage Site. Hawaiians constructed oceanic fish ponds. A remarkable example is the "Menehune" fishpond dating from at least 1,000 years ago, at Alekoko.
Legend says. In the first half of the 18th century, German Stephan Ludwig Jacobi experimented with external fertilization of brown trouts and salmon, he wrote an article "Von der künstlichen Erzeugung der Forellen und Lachse". By the latter decades of the 18th century, oyster farming had begun in estuaries along the Atlantic Coast of North America; the word aquaculture appeared in an 1855 newspaper article in reference to the harvesting of ice. It appeared in descriptions of the terrestrial agricultural practise of subirrigation in the late 19th century before becoming associated with the cultivation of aquatic plant and animal species. In 1859, Stephen Ainsworth of West Bloomfield, New York, began experiments with brook trout. By 1864, Seth Green had established a commercial fish-hatching operation at Caledonia Springs, near Rochester, New York. By 1866, with the involvement of Dr. W. W. Fletcher of Concord, artificial fish hatcheries were under way in both Canada and the United States; when the Dildo Island fish hatchery opened in Newfoundland in 1889, it was the largest and most advanced in the world.
The word aquaculture was used in descriptions of the hatcheries experiments with cod and lobster in 1890. By the 1920s, the American Fish Culture Company of Carolina, Rhode Island, founded in the 1870s was one of the leading producers of trout. During the 1940s, they had perfected the method of manipulating the day and night cycle of fish so that they could be artificially spawned year around. Californians harvested wild kelp and attempted to manage supply around 1900 labeling it a wartime resource. Harvest stagnation in wild fisheries and overexploitation of popular marine species, combined with a growing demand for high-quality protein, encouraged aquaculturists to domesticate other marine species. At the outset of modern aquaculture, many were optimistic that a "Blue Revolution" could take place in aquaculture, just as the Green Revolution of the 20th century had revolutionized agriculture. Although land animals had long been domesticated, most seafood species were still caught from the wild.
Concerned about the impact of growing demand for seafood on the world's oceans, prominent ocean explorer Jacques Cousteau wrote in 1973: "With earth's burgeoning human populations to feed, we must turn to the sea with new understanding and new technology."About 430 of the species cultu
An aquarium is a vivarium of any size having at least one transparent side in which aquatic plants or animals are kept and displayed. Fishkeepers use aquaria to keep fish, amphibians, aquatic reptiles such as turtles, aquatic plants; the term "aquarium", coined by English naturalist Philip Henry Gosse, combines the Latin root aqua, meaning water, with the suffix -arium, meaning "a place for relating to". The aquarium principle was developed in 1850 by the chemist Robert Warington, who explained that plants added to water in a container would give off enough oxygen to support animals, so long as the numbers of animals did not grow too large; the aquarium craze was launched in early Victorian England by Gosse, who created and stocked the first public aquarium at the London Zoo in 1853, published the first manual, The Aquarium: An Unveiling of the Wonders of the Deep Sea in 1854. An aquarium is a water-filled tank. Small aquariums are kept in the home by hobbyists. There are larger public aquariums in many cities.
This kind of aquarium is other aquatic animals in large tanks. A large aquarium may have otters, turtles and other sea animals. Most aquarium tanks have plants. An aquarist owns fish or maintains an aquarium constructed of glass or high-strength acrylic. Cuboid aquaria are known as fish tanks or tanks, while bowl-shaped aquaria are known as fish bowls. Size can range from a small glass bowl, under a gallon in volume, to immense public aquaria of several thousand gallons. Specialized equipment maintains appropriate water quality and other characteristics suitable for the aquarium's residents. In 1369, the Hongwu Emperor of China established a porcelain company that produced large porcelain tubs for maintaining goldfish. Leonhard Baldner, who wrote Vogel-, Fisch- und Tierbuch in 1666, maintained weather loaches and newts, it is sometimes held that the aquarium was invented by the Romans, who are said to have kept sea barbels in marble-and-glass tanks, but this is unlikely to be true. In 1832, Jeanne Villepreux-Power, a pioneering French marine biologist, became the first person to create aquaria for experimenting with aquatic organisms.
In 1836, soon after his invention of the Wardian case, Dr. Nathaniel Bagshaw Ward proposed to use his tanks for tropical animals. In 1841 he did so, though only with toy fish. However, he soon housed real animals. In 1838, Félix Dujardin noted owning a saltwater aquarium. In 1846, Anne Thynne maintained stony corals and seaweed for three years, was credited as the creator of the first balanced marine aquarium in London. English chemist Robert Warington experimented with a 13-gallon container, which contained goldfish and snails, creating one of the first stable aquaria; the aquarium principle was developed by Warington, explaining that plants added to water in a container would give off enough oxygen to support animals, so long as their numbers do not grow too large. He published his findings in 1850 in the Chemical Society's journal; the keeping of fish in an aquarium spread quickly. In the United Kingdom, it became popular after ornate aquaria in cast-iron frames were featured at the Great Exhibition of 1851.
In 1853, the aquarium craze was launched in England by Philip Henry Gosse who created and stocked the first public aquarium in the London Zoo which came to be known as the Fish House. Gosse coined the word "aquarium", opting for this term in 1854 in his book The Aquarium: An Unveiling of the Wonders of the Deep Sea. In this book, Gosse discussed saltwater aquaria. In the 1850s, the aquarium became a fad in the United Kingdom. Tank designs and techniques for maintaining water quality were developed by Warington cooperating with Gosse until his critical review of the tank water composition. Edward Edwards developed these glass-fronted aquaria in his 1858 patent for a "dark-water-chamber slope-back tank", with water circulating to a reservoir beneath. Germans soon rivaled the British in their interest. In 1854, an anonymous author had two articles published about the saltwater aquaria of the United Kingdom: Die Gartenlaube entitled Der Ocean auf dem Tische. However, in 1856, Der See im Glase was published, discussing freshwater aquaria, which were much easier to maintain in landlocked areas.
In 1862 William Alford Lloyd bankrupt because of the craze in England being over, moved to Grindel Dammthor, Hamburg, to supervise the installation of the circulating system and tanks at the Hamburg Aquarium. During the 1870s, some of the first aquarist societies were appearing in Germany; the United States soon followed. Published in 1858, Henry D. Butler's The Family Aquarium was one of the first books written in the United States about the aquarium. According to the July issue of The North American Review of the same year, William Stimson may have owned some of the first functional aquaria, had as many as seven or eight; the first aquarist society in the United States was founded in New York City in 1893, followed by others. The New York Aquarium Journal, first published in October 1876, is considered to be the world's first aquarium magazine. In the Victorian era in the United Kingdom, a common design for the home aquarium was a glass front with the other sides made of wood; the bottom would be heated from below.
More advanced systems soon began to be introduced, along with tanks of
A reef is a bar of rock, coral or similar material, lying beneath the surface of water. Many reefs result from natural, abiotic processes—deposition of sand, wave erosion planing down rock outcrops, etc.—but the best known reefs are the coral reefs of tropical waters developed through biotic processes dominated by corals and coralline algae. Artificial reefs sometimes have a role in enhancing the physical complexity of featureless sand bottoms, in order to attract a diverse assemblage of organisms algae and fish. Earth's largest reef system is the Great Barrier Reef in Australia, at a length of over 2,300 kilometres. There is a variety of biotic reef types, including oyster reefs and sponge reefs, but the most massive and distributed are tropical coral reefs. Although corals are major contributors to the framework and bulk material comprising a coral reef; these biotic reef types take on additional names depending upon how the reef lies in relation to the land, if any. Reef types include fringing reefs, barrier reefs, atolls.
A fringing reef is a reef, attached to an island. A barrier reef forms a calcareous barrier around an island resulting in a lagoon between the shore and the reef. An atoll is a ring reef with no land present; the reef front is a high energy locale whereas the internal lagoon will be at a lower energy with fine grained sediments. Ancient reefs buried within stratigraphic sections are of considerable interest to geologists because they provide paleo-environmental information about the location in Earth's history. In addition, reef structures within a sequence of sedimentary rocks provide a discontinuity which may serve as a trap or conduit for fossil fuels or mineralizing fluids to form petroleum or ore deposits. Corals, including some major extinct groups Rugosa and Tabulata, have been important reef builders through much of the Phanerozoic since the Ordovician Period. However, other organism groups, such as calcifying algae members of the red algae Rhodophyta, molluscs have created massive structures at various times.
During the Cambrian Period, the conical or tubular skeletons of Archaeocyatha, an extinct group of uncertain affinities, built reefs. Other groups, such as the Bryozoa have been important interstitial organisms, living between the framework builders; the corals which build reefs today, the Scleractinia, arose after the Permian–Triassic extinction event that wiped out the earlier rugose corals, became important reef builders throughout the Mesozoic Era. They may have arisen from a rugose coral ancestor. Rugose corals built their skeletons of calcite and have a different symmetry from that of the scleractinian corals, whose skeletons are aragonite. However, there are some unusual examples of well-preserved aragonitic rugose corals in the late Permian. In addition, calcite has been reported in the initial post-larval calcification in a few scleractinian corals. Scleractinian corals may have arisen from a non-calcifying ancestor independent of the rugosan corals. One useful definition distinguishes reefs from mounds as follows: Both are considered to be varieties of organosedimentary buildups – sedimentary features, built by the interaction of organisms and their environment, that have synoptic relief and whose biotic composition differs from that found on and beneath the surrounding sea floor.
Reefs are held up by a macroscopic skeletal framework. Coral reefs are an example of this kind. Corals and calcareous algae grow on top of one another and form a three-dimensional framework, modified in various ways by other organisms and inorganic processes. By contrast, mounds lack a macroscopic skeletal framework. Mounds are built by organisms that don't grow a skeletal framework. A microbial mound might be built or by cyanobacteria. Examples of biostromes formed by cyanobacteria occur in the Great Salt Lake in Utah, in Shark Bay on the coast of Western Australia. Cyanobacteria do not have skeletons, individuals are microscopic. Cyanobacteria can encourage the precipitation or accumulation of calcium carbonate to produce distinct sediment bodies in composition that have relief on the seafloor. Cyanobacterial mounds were most abundant before the evolution of shelly macroscopic organisms, but they still exist today. Bryozoans and crinoids, common contributors to marine sediments during the Mississippian, for instance, produced a different kind of mound.
Bryozoans are small and the skeletons of crinoids disintegrate. However and crinoid meadows can persist over time and produce compositionally distinct bodies of sediment with depositional relief; the Proterozoic Belt Supergroup contains evidence of possible microbial mat and dome structures similar to stromatolite reef complexes. Benjamin Kahn Coral reef Reef Hobbyist Magazine Placer Pseudo-atoll Shears N. T. Biogeography, community structure and biological habitat types of subtidal reefs on the South Island West Coast, New Zealand. Science for Conservation 281. P 53. Department of Conservation, New Zealand. Reef Rescue - Smithsonian Ocean Portal Coral Reefs of the Tropics: facts and movies from The Nature Conservancy NOAA Photo Library Reef Environmental Education Foundation NOS Data Explorer - A portal to obtain NOAA National Ocean Service data Reef formation Atoll
In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring by sexual reproduction. Other ways of defining species include their karyotype, DNA sequence, behaviour or ecological niche. In addition, paleontologists use the concept of the chronospecies since fossil reproduction cannot be examined. While these definitions may seem adequate, when looked at more they represent problematic species concepts. For example, the boundaries between related species become unclear with hybridisation, in a species complex of hundreds of similar microspecies, in a ring species. Among organisms that reproduce only asexually, the concept of a reproductive species breaks down, each clone is a microspecies. All species are given a two-part name, a "binomial"; the first part of a binomial is the genus.
The second part is called the specific epithet. For example, Boa constrictor is one of four species of the genus Boa. None of these is satisfactory definitions, but scientists and conservationists need a species definition which allows them to work, regardless of the theoretical difficulties. If species were fixed and distinct from one another, there would be no problem, but evolutionary processes cause species to change continually, to grade into one another. Species were seen from the time of Aristotle until the 18th century as fixed kinds that could be arranged in a hierarchy, the great chain of being. In the 19th century, biologists grasped. Charles Darwin's 1859 book The Origin of Species explained how species could arise by natural selection; that understanding was extended in the 20th century through genetics and population ecology. Genetic variability arises from mutations and recombination, while organisms themselves are mobile, leading to geographical isolation and genetic drift with varying selection pressures.
Genes can sometimes be exchanged between species by horizontal gene transfer. Viruses are a special case, driven by a balance of mutation and selection, can be treated as quasispecies. Biologists and taxonomists have made many attempts to define species, beginning from morphology and moving towards genetics. Early taxonomists such as Linnaeus had no option but to describe what they saw: this was formalised as the typological or morphological species concept. Ernst Mayr emphasised reproductive isolation, but this, like other species concepts, is hard or impossible to test. Biologists have tried to refine Mayr's definition with the recognition and cohesion concepts, among others. Many of the concepts are quite similar or overlap, so they are not easy to count: the biologist R. L. Mayden recorded about 24 concepts, the philosopher of science John Wilkins counted 26. Wilkins further grouped the species concepts into seven basic kinds of concepts: agamospecies for asexual organisms biospecies for reproductively isolated sexual organisms ecospecies based on ecological niches evolutionary species based on lineage genetic species based on gene pool morphospecies based on form or phenotype and taxonomic species, a species as determined by a taxonomist.
A typological species is a group of organisms in which individuals conform to certain fixed properties, so that pre-literate people recognise the same taxon as do modern taxonomists. The clusters of variations or phenotypes within specimens would differentiate the species; this method was used as a "classical" method of determining species, such as with Linnaeus early in evolutionary theory. However, different phenotypes are not different species. Species named in this manner are called morphospecies. In the 1970s, Robert R. Sokal, Theodore J. Crovello and Peter Sneath proposed a variation on this, a phenetic species, defined as a set of organisms with a similar phenotype to each other, but a different phenotype from other sets of organisms, it differs from the morphological species concept in including a numerical measure of distance or similarity to cluster entities based on multivariate comparisons of a reasonably large number of phenotypic traits. A mate-recognition species is a group of sexually reproducing organisms that recognize one another as potential mates.
Expanding on this to allow for post-mating isolation, a cohesion species is the most inclusive population of individuals having the potential for phenotypic cohesion through intrinsic cohesion mechanisms. A further development of the recognition concept is provided by the biosemiotic concept of species. In microbiology, genes can move even between distantly related bacteria extending to the whole bacterial domain; as a rule of thumb, microbiologists have assumed that kinds of Bacteria or Archaea with 16S ribosomal RNA gene sequences more similar than 97% to each other need to be checked by DNA-DNA hybridisation to decide if they belong to the same species or not. This concept was narrowed in 2006 to a similarity of 98.7%. DNA-DNA hybri
A chordate is an animal constituting the phylum Chordata. During some period of their life cycle, chordates possess a notochord, a dorsal nerve cord, pharyngeal slits, an endostyle, a post-anal tail: these five anatomical features define this phylum. Chordates are bilaterally symmetric; the Chordata and Ambulacraria together form the superphylum Deuterostomia. Chordates are divided into three subphyla: Vertebrata. There are extinct taxa such as the Vetulicolia. Hemichordata has been presented as a fourth chordate subphylum, but now is treated as a separate phylum: hemichordates and Echinodermata form the Ambulacraria, the sister phylum of the Chordates. Of the more than 65,000 living species of chordates, about half are bony fish that are members of the superclass Osteichthyes. Chordate fossils have been found from as early as the Cambrian explosion, 541 million years ago. Cladistically, vertebrates - chordates with the notochord replaced by a vertebral column during development - are considered to be a subgroup of the clade Craniata, which consists of chordates with a skull.
The Craniata and Tunicata compose the clade Olfactores. Chordates form a phylum of animals that are defined by having at some stage in their lives all of the following anatomical features: A notochord, a stiff rod of cartilage that extends along the inside of the body. Among the vertebrate sub-group of chordates the notochord develops into the spine, in wholly aquatic species this helps the animal to swim by flexing its tail. A dorsal neural tube. In fish and other vertebrates, this develops into the spinal cord, the main communications trunk of the nervous system. Pharyngeal slits; the pharynx is the part of the throat behind the mouth. In fish, the slits are modified to form gills, but in some other chordates they are part of a filter-feeding system that extracts particles of food from the water in which the animals live. Post-anal tail. A muscular tail that extends backwards behind the anus. An endostyle; this is a groove in the ventral wall of the pharynx. In filter-feeding species it produces mucus to gather food particles, which helps in transporting food to the esophagus.
It stores iodine, may be a precursor of the vertebrate thyroid gland. There are soft constraints that separate chordates from certain other biological lineages, but are not part of the formal definition: All chordates are deuterostomes; this means. All chordates are based on a bilateral body plan. All chordates are coelomates, have a fluid filled body cavity called a coelom with a complete lining called peritoneum derived from mesoderm; the following schema is from the third edition of Vertebrate Palaeontology. The invertebrate chordate classes are from Fishes of the World. While it is structured so as to reflect evolutionary relationships, it retains the traditional ranks used in Linnaean taxonomy. Phylum Chordata †Vetulicolia? Subphylum Cephalochordata – Class Leptocardii Clade Olfactores Subphylum Tunicata – Class Ascidiacea Class Thaliacea Class Appendicularia Class Sorberacea Subphylum Vertebrata Infraphylum incertae sedis Cyclostomata Superclass'Agnatha' paraphyletic Class Myxini Class Petromyzontida or Hyperoartia Class †Conodonta Class †Myllokunmingiida Class †Pteraspidomorphi Class †Thelodonti Class †Anaspida Class †Cephalaspidomorphi Infraphylum Gnathostomata Class †Placodermi Class Chondrichthyes Class †Acanthodii Superclass Osteichthyes Class Actinopterygii Class Sarcopterygii Superclass Tetrapoda Class Amphibia Class Sauropsida Class Synapsida Craniates, one of the three subdivisions of chordates, all have distinct skulls.
They include the hagfish. Michael J. Benton commented that "craniates are characterized by their heads, just as chordates, or all deuterostomes, are by their tails". Most craniates are vertebrates; these consist of a series of bony or cartilaginous cylindrical vertebrae with neural arches that protect the spinal cord, with projections that link the vertebrae. However hagfish have incomplete braincases and no vertebrae, are therefore not regarded as vertebrates, but as members of the craniates, the group from which vertebrates are thought to have evolved; however the cladistic exclusion of hagfish from the vertebrates is controversial, as they ma
Snappers are a family of perciform fish, Lutjanidae marine, but with some members inhabiting estuaries, feeding in fresh water. The family includes about 113 species; some are important food fish. One of the best known is the red snapper. Snappers inhabit subtropical regions of all oceans; some snappers grow up to about 1 m in length however one specific Snapper, the Cubera Snapper, grows up to 5 ft in length. Most are active carnivores, feeding on other fish, though a few are plankton-feeders, they can be kept in aquaria, but grow too fast to be popular aquarium fish. Most species live at depths reaching 100 m near coral reefs, but some species are found up to 500 m deep; as other fish, snappers harbour parasites. A detailed study conducted in New Caledonia has shown that coral reef-associated snappers harbour about 9 species of parasites per fish species. Subfamily Apsilinae genus Apsilus Valenciennes in Cuvier et Valenciennes, 1830 genus Lipocheilus Anderson, Talwar et Johnson, 1977 genus Paracaesio Bleeker, 1875 genus Parapristipomoides Kami, 1973 subfamily Etelinae genus Aphareus Cuvier in Cuvier et Valenciennes, 1830 genus Aprion Valenciennes in Cuvier et Valenciennes, 1830 genus Etelis Cuvier In Cuvier et Valenciennes, 1828 genus Pristipomoides Bleeker, 1852 genus Randallichthys Anderson, Kami et Johnson, 1977 subfamily Lutjaninae genus Hoplopagrus Gill, 1861 genus Lutjanus Bloch, 1790 genus Macolor Bleeker, 1860 genus Ocyurus Gill, 1862 genus Pinjalo Bleeker, 1873 genus Rhomboplites Gill, 1862 subfamily Paradichthyinae genus Symphorichthys Munro, 1967 genus Symphorus Günther, 1872
In scientific nomenclature, a synonym is a scientific name that applies to a taxon that goes by a different scientific name, although the term is used somewhat differently in the zoological code of nomenclature. For example, Linnaeus was the first to give a scientific name to the Norway spruce, which he called Pinus abies; this name is no longer in use: it is now a synonym of the current scientific name, Picea abies. Unlike synonyms in other contexts, in taxonomy a synonym is not interchangeable with the name of which it is a synonym. In taxonomy, synonyms have a different status. For any taxon with a particular circumscription and rank, only one scientific name is considered to be the correct one at any given time. A synonym cannot exist in isolation: it is always an alternative to a different scientific name. Given that the correct name of a taxon depends on the taxonomic viewpoint used a name, one taxonomist's synonym may be another taxonomist's correct name. Synonyms may arise whenever the same taxon is named more than once, independently.
They may arise when existing taxa are changed, as when two taxa are joined to become one, a species is moved to a different genus, a variety is moved to a different species, etc. Synonyms come about when the codes of nomenclature change, so that older names are no longer acceptable. To the general user of scientific names, in fields such as agriculture, ecology, general science, etc. A synonym is a name, used as the correct scientific name but, displaced by another scientific name, now regarded as correct, thus Oxford Dictionaries Online defines the term as "a taxonomic name which has the same application as another one, superseded and is no longer valid." In handbooks and general texts, it is useful to have synonyms mentioned as such after the current scientific name, so as to avoid confusion. For example, if the much advertised name change should go through and the scientific name of the fruit fly were changed to Sophophora melanogaster, it would be helpful if any mention of this name was accompanied by "".
Synonyms used in this way may not always meet the strict definitions of the term "synonym" in the formal rules of nomenclature which govern scientific names. Changes of scientific name have two causes: they may be taxonomic or nomenclatural. A name change may be caused by changes in the circumscription, position or rank of a taxon, representing a change in taxonomic, scientific insight. A name change may be due to purely nomenclatural reasons, that is, based on the rules of nomenclature. Speaking in general, name changes for nomenclatural reasons have become less frequent over time as the rules of nomenclature allow for names to be conserved, so as to promote stability of scientific names. In zoological nomenclature, codified in the International Code of Zoological Nomenclature, synonyms are different scientific names of the same taxonomic rank that pertain to that same taxon. For example, a particular species could, over time, have had two or more species-rank names published for it, while the same is applicable at higher ranks such as genera, orders, etc.
In each case, the earliest published name is called the senior synonym, while the name is the junior synonym. In the case where two names for the same taxon have been published the valid name is selected accorded to the principle of the first reviser such that, for example, of the names Strix scandiaca and Strix noctua, both published by Linnaeus in the same work at the same date for the taxon now determined to be the snowy owl, the epithet scandiaca has been selected as the valid name, with noctua becoming the junior synonym. One basic principle of zoological nomenclature is that the earliest published name, the senior synonym, by default takes precedence in naming rights and therefore, unless other restrictions interfere, must be used for the taxon. However, junior synonyms are still important to document, because if the earliest name cannot be used the next available junior synonym must be used for the taxon. For other purposes, if a researcher is interested in consulting or compiling all known information regarding a taxon, some of this may well have been published under names now regarded as outdated and so it is again useful to know a list of historic synonyms which may have been used for a given current taxon name.
Objective synonyms refer to taxa with same rank. This may be species-group taxa of the same rank with the same type specimen, genus-group taxa of the same rank with the same type species or if their type species are themselves objective synonyms, of family-group taxa with the same type genus, etc. In the case of subjective synonyms, there is no such shared type, so the synonymy is open to taxonomic judgement, meaning that th