Priapulida, sometimes referred to as penis worms, is a phylum of unsegmented marine worms. The name of the phylum relates to the Greek god of fertility, because their general shape and their extensible spiny introvert may recall the shape of a penis, they live in comparatively shallow waters up to 90 metres deep. Some species show a remarkable tolerance for hydrogen anoxia, they can be quite abundant in some areas. In an Alaskan bay as many as 85 adult individuals of Priapulus caudatus per square meter has been recorded, while the density of its larvae can be as high as 58,000 per square meter. Together with Echiura and Sipuncula, they were once placed in the taxon Gephyrea, but consistent morphological and molecular evidence supports their belonging to Ecdysozoa, which includes arthropods and nematodes. Fossil findings show that the mouth design of the stem-arthropod Pambdelurion is identical with that of priapulids, indicating that their mouth is an original trait inherited from the last common ancestor of both priapulids and arthropods if modern arthropods no longer possess it.
Among Ecdysozoa, their nearest relatives are Kinorhyncha and Loricifera, with which they constitute the Scalidophora clade named after the spines covering the introvert. They feed on slow-moving invertebrates, such as polychaete worms. Priapulid-like fossils are known at least as far back as the Middle Cambrian, they were major predators of the Cambrian period. However, crown-group priapulids cannot be recognized until the Carboniferous. About 20 extant species of priapulid worms are known, half of them being of meiobenthic size. Priapulids are cylindrical worm-like animals, ranging from 0.2–0.3 to 39 centimetres long, with a median anterior mouth quite devoid of any armature or tentacles. The body is divided into a main trunk or abdomen and a somewhat swollen proboscis region ornamented with longitudinal ridges; the body is ringed and has circles of spines, which are continued into the protrusible pharynx. Some species may have a tail or a pair of caudal appendages; the body has a chitinous cuticle, moulted as the animal grows.
There is a wide body-cavity, which has no connection with the renal or reproductive organs, so it is not a coelom. There are no vascular or respiratory systems, but the body cavity does contain phagocytic amoebocytes and cells containing the respiratory pigment haemerythrin; the alimentary canal is straight, consisting of an eversible pharynx, an intestine, a short rectum. The pharynx is lined by teeth; the anus is terminal, although in Priapulus one or two hollow ventral diverticula of the body-wall stretch out behind it. The nervous system consists of a nerve ring around the pharynx and a prominent cord running the length of the body with ganglia and longitudinal and transversal neurites consistent with an orthogonal organisation; the nervous system retains a basiepidermal configuration with a connection with the ectoderm, forming part of the body wall. There are no specialized sense organs, but there are sensory nerve endings in the body on the proboscis; the priapulids are gonochoristic, having two separate sexes Their male and female organs are associated with the excretory protonephridia.
They comprise a pair of branching tufts, each of which opens to the exterior on one side of the anus. The tips of these tufts enclose a flame-cell like those found in flatworms and other animals, these function as excretory organs; as the animals mature, diverticula arise on the tubes of these organs, which develop either spermatozoa or ova. These sex cells pass out through the ducts; the perigenital area of the genus Tubiluchus exhibit sexual dimorphism. Priapulid development has been reappraised because early studies reported abnormal development caused by high temperature of embryo culture. For the species Priapulus caudatus, the 80 µm egg undergoes a total and radial cleavage following a symmetrical and subequal pattern. Development is remarkably slow, with the first cleavage taking place 15 hours after fertilization, gastrulation after several days and hatching of the first'lorica' larvae after 15 to 20 days; the species Meiopriapulus fijiensis have direct development. In current systematics, they are described as protostomes, despite having a deuterostomic development.
Because the group is so ancient, it is assumed the deuterostome condition which appears to be ancestral for bilaterians have been maintained. Stem-group priapulids are known from the Middle Cambrian Burgess Shale, where their soft-part anatomy is preserved in conjunction with their gut contents – allowing a reconstruction of their diets. In addition, isolated microfossils are widespread in Cambrian deposits, allowing the distribution of priapulids – and individual species – to be tracked through Cambrian oceans. Trace fossils that are morphologically identical to modern priapulid burrows mark the start of the Cambrian period, suggesting that priapulids, or at least close anatomical relatives, evolved around this time. Crown-group priapulid body fossils are first known from the Carboniferous. Uncertain relationship "Class" PalaeoscolecidaStem-group Priapulida Class †Archaeopriapulida Family †Ottoiidae Genus †Ancalagon Genus †Fieldia Genus †Lecythioscopa Genus †Ottoia Genus †Scolecofurca Genus †Selkirkia Family †Louisellidae Genus †Anningvermis Genus †Corynetis Genus †LouisellaPhylum Priapulida Class Priapulimorpha Order Priapulimorphida Family Priapulidae G
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
International Standard Serial Number
An International Standard Serial Number is an eight-digit serial number used to uniquely identify a serial publication, such as a magazine. The ISSN is helpful in distinguishing between serials with the same title. ISSN are used in ordering, interlibrary loans, other practices in connection with serial literature; the ISSN system was first drafted as an International Organization for Standardization international standard in 1971 and published as ISO 3297 in 1975. ISO subcommittee TC 46/SC 9 is responsible for maintaining the standard; when a serial with the same content is published in more than one media type, a different ISSN is assigned to each media type. For example, many serials are published both in electronic media; the ISSN system refers to these types as electronic ISSN, respectively. Conversely, as defined in ISO 3297:2007, every serial in the ISSN system is assigned a linking ISSN the same as the ISSN assigned to the serial in its first published medium, which links together all ISSNs assigned to the serial in every medium.
The format of the ISSN is an eight digit code, divided by a hyphen into two four-digit numbers. As an integer number, it can be represented by the first seven digits; the last code digit, which may be 0-9 or an X, is a check digit. Formally, the general form of the ISSN code can be expressed as follows: NNNN-NNNC where N is in the set, a digit character, C is in; the ISSN of the journal Hearing Research, for example, is 0378-5955, where the final 5 is the check digit, C=5. To calculate the check digit, the following algorithm may be used: Calculate the sum of the first seven digits of the ISSN multiplied by its position in the number, counting from the right—that is, 8, 7, 6, 5, 4, 3, 2, respectively: 0 ⋅ 8 + 3 ⋅ 7 + 7 ⋅ 6 + 8 ⋅ 5 + 5 ⋅ 4 + 9 ⋅ 3 + 5 ⋅ 2 = 0 + 21 + 42 + 40 + 20 + 27 + 10 = 160 The modulus 11 of this sum is calculated. For calculations, an upper case X in the check digit position indicates a check digit of 10. To confirm the check digit, calculate the sum of all eight digits of the ISSN multiplied by its position in the number, counting from the right.
The modulus 11 of the sum must be 0. There is an online ISSN checker. ISSN codes are assigned by a network of ISSN National Centres located at national libraries and coordinated by the ISSN International Centre based in Paris; the International Centre is an intergovernmental organization created in 1974 through an agreement between UNESCO and the French government. The International Centre maintains a database of all ISSNs assigned worldwide, the ISDS Register otherwise known as the ISSN Register. At the end of 2016, the ISSN Register contained records for 1,943,572 items. ISSN and ISBN codes are similar in concept. An ISBN might be assigned for particular issues of a serial, in addition to the ISSN code for the serial as a whole. An ISSN, unlike the ISBN code, is an anonymous identifier associated with a serial title, containing no information as to the publisher or its location. For this reason a new ISSN is assigned to a serial each time it undergoes a major title change. Since the ISSN applies to an entire serial a new identifier, the Serial Item and Contribution Identifier, was built on top of it to allow references to specific volumes, articles, or other identifiable components.
Separate ISSNs are needed for serials in different media. Thus, the print and electronic media versions of a serial need separate ISSNs. A CD-ROM version and a web version of a serial require different ISSNs since two different media are involved. However, the same ISSN can be used for different file formats of the same online serial; this "media-oriented identification" of serials made sense in the 1970s. In the 1990s and onward, with personal computers, better screens, the Web, it makes sense to consider only content, independent of media; this "content-oriented identification" of serials was a repressed demand during a decade, but no ISSN update or initiative occurred. A natural extension for ISSN, the unique-identification of the articles in the serials, was the main demand application. An alternative serials' contents model arrived with the indecs Content Model and its application, the digital object identifier, as ISSN-independent initiative, consolidated in the 2000s. Only in 2007, ISSN-L was defined in the
Cnidaria is a phylum under Kingdom Animalia containing over 11,000 species of animals found in aquatic environments: they are predominantly marine. Their distinguishing feature is cnidocytes, specialized cells that they use for capturing prey, their bodies consist of mesoglea, a non-living jelly-like substance, sandwiched between two layers of epithelium that are one cell thick. They have two basic body forms: swimming medusae and sessile polyps, both of which are radially symmetrical with mouths surrounded by tentacles that bear cnidocytes. Both forms have a single body cavity that are used for digestion and respiration. Many cnidarian species produce colonies that are single organisms composed of medusa-like or polyp-like zooids, or both. Cnidarians' activities are coordinated by simple receptors. Several free-swimming species of Cubozoa and Scyphozoa possess balance-sensing statocysts, some have simple eyes. Not all cnidarians reproduce sexually, with many species having complex life cycles of asexual polyp stages and sexual medusae.
Some, omit either the polyp or the medusa stage. Cnidarians were grouped with ctenophores in the phylum Coelenterata, but increasing awareness of their differences caused them to be placed in separate phyla. Cnidarians are classified into four main groups: the wholly sessile Anthozoa. Staurozoa have been recognised as a class in their own right rather than a sub-group of Scyphozoa, the parasitic Myxozoa and Polypodiozoa were only recognized as cnidarians in 2007. Most cnidarians prey on organisms ranging in size from plankton to animals several times larger than themselves, but many obtain much of their nutrition from dinoflagellates, a few are parasites. Many are preyed on by other animals including starfish, sea slugs, fish and other cnidarians. Many scleractinian corals—which form the structural foundation for coral reefs—possess polyps that are filled with symbiotic photo-synthetic zooxanthellae. While reef-forming corals are entirely restricted to warm and shallow marine waters, other cnidarians can be found at great depths, in polar regions, in freshwater.
Recent phylogenetic analyses support monophyly of cnidarians, as well as the position of cnidarians as the sister group of bilaterians. Fossil cnidarians have been found in rocks formed about 580 million years ago, other fossils show that corals may have been present shortly before 490 million years ago and diversified a few million years later. However, molecular clock analysis of mitochondrial genes suggests a much older age for the crown group of cnidarians, estimated around 741 million years ago 200 million years before the Cambrian period as well as any fossils. Cnidarians form a phylum of animal that are more complex than sponges, about as complex as ctenophores, less complex than bilaterians, which include all other animals. Both cnidarians and ctenophores are more complex than sponges as they have: cells bound by inter-cell connections and carpet-like basement membranes. Cnidarians are distinguished from all other animals by having cnidocytes that fire harpoon like structures and are used to capture prey.
In some species, cnidocytes can be used as anchors. Like sponges and ctenophores, cnidarians have two main layers of cells that sandwich a middle layer of jelly-like material, called the mesoglea in cnidarians. Hence and ctenophores have traditionally been labelled diploblastic, along with sponges. However, both cnidarians and ctenophores have a type of muscle that, in more complex animals, arises from the middle cell layer; as a result, some recent text books classify ctenophores as triploblastic, it has been suggested that cnidarians evolved from triploblastic ancestors. Most adult cnidarians appear as either free-swimming medusae or sessile polyps, many hydrozoans species are known to alternate between the two forms. Both are radially symmetrical, like a tube respectively. Since these animals have no heads, their ends are described as "oral" and "aboral". Most have fringes of tentacles equipped with cnidocytes around their edges, medusae have an inner ring of tentacles around the mouth; some hydroids may consist of colonies of zooids that serve different purposes, such as defense and catching prey.
The mesoglea of polyps is thin and soft, but that of medusae is thick and springy, so that it returns to its original shape after muscles around the edge have contracted to squeeze water out, enabling medusae to swim by a sort of jet propulsion. In medusae the only supporting structure is the mesoglea. Hydra and most sea anemones close their mouths when they are not feeding, the water in the digestive cavity acts as a hydrostatic skeleton, rather like a water-filled balloon. Other polyps such as Tubularia use columns of water-filled cells for support. Sea pens stiffen the mesoglea with calcium carbonate spicules and tough fibrous proteins, rather like sponges. In some colonial polyps, a chitinous periderm gives support and some protection to the connecting sections and to the lower parts of individual polyps. Stony corals secrete massive calcium carbonate exoske
Archaeopriapulida is a group of priapulid-like worms known from Cambrian lagerstätte. The group is related to, similar to, the modern Priapulids, it is unclear. Despite a remarkable morphological similarity to their modern cousins, they fall outside of the priapulid crown group, not unambiguously represented in the fossil record until the Carboniferous, they are closely related or paraphyletic to the palaeoscolecids.
Protostomia is a clade of animals. Together with the deuterostomes and xenacoelomorpha, its members make up the Bilateria comprising animals with bilateral symmetry and three germ layers; the major distinctions between deuterostomes and protostomes are found in embryonic development and is based on the embryological origins of the mouth and anus. In most, but not all protostomes, the mouth forms first the anus, whereas the reverse is true in deuterostomes. In animals at least as complex as earthworms, the embryo forms a dent on one side, the blastopore, which deepens to become the archenteron, the first phase in the growth of the gut. In deuterostomes, the original dent becomes the anus while the gut tunnels through to make another opening, which forms the mouth; the protostomes were so named because it was once believed that in all cases the embryological dent formed the mouth while the anus was formed at the opening made by the other end of the gut. It is now known that the fate of the blastopore in protostomes is variable.
While the evolutionary distinction between deuterostomes and protostomes remains valid, the descriptive accuracy of the name'protostome' is disputable. Protostomes and deuterostomes differ in several ways. Early in development, deuterostome embryos undergo radial cleavage during cell division, while many protostomes undergo spiral cleavage. Animals from both groups possess a complete digestive tract, but in protostomes the first opening of the embryonic gut develops into the mouth, the anus forms secondarily. In deuterostomes, the anus forms first. Most protostomes have schizocoelous development, where cells fill in the interior of the gastrula to form the mesoderm. In deuterostomes, the mesoderm forms through invagination of the endoderm; the common ancestor of protostomes and deuterostomes was evidently a worm-like aquatic animal. The two clades diverged about 600 million years ago. Protostomes evolved into over a million species alive today, compared to about 60,000 deuterostome species. Protostomes are divided into e.g. arthropods, nematodes.
A modern consensus phylogenetic tree for the protostomes is shown below. The timing of clades radiating into newer clades is given in mya; the Taxonomicon for Karl Grobben Media related to Protostomia at Wikimedia Commons
Philosophical Transactions of the Royal Society B
Philosophical Transactions of the Royal Society B: Biological Sciences is a biweekly peer-reviewed scientific journal published by the Royal Society. The editor-in-chief is John Pickett; each issue covers a specific area of the biological sciences. Each issue aims to create an original and authoritative synthesis bridging traditional disciplines, which showcases current developments and provides a foundation for future research and policy decisions; each issue is edited by one or more expert guest editors. The themes fall into one of four general categories: Cell and Development Health and Disease Environment and Evolution Neuroscience and CognitionAll articles become accessible one year after their publication date. Philosophical Transactions of the Royal Society was established in 1665 by the Royal Society and is the oldest scientific journal in the English-speaking world. Henry Oldenburg was appointed as the first secretary to the society and he was the first editor of the society's journal.
In 1887 the journal expanded to become two separate publications, one serving the physical sciences, Philosophical Transactions of the Royal Society A: Mathematical and Engineering Sciences, the other focusing on the life sciences, Philosophical Transactions of the Royal Society B: Biological Sciences. Nowadays, both journals publish themed issues and discussion meeting issues, while individual research articles are published in the sister journal Proceedings of the Royal Society; the journal celebrated its 350th anniversary in 2015. To commemorate this event it published a special collection of commentaries on landmark papers from the archive by scientists such as Antonie van Leeuwenhoek, Hans Sloane and Alan Turing. Official website Royal Society Publishing 350th anniversary History of Philosophical Transactions