57-454: Entoprocta / ɛ n t oʊ ˈ p r ɒ k t ə / ( lit. ' inside rectum/anus ' ), or Kamptozoa / k æ m ( p ) t ə ˈ z oʊ ə / , is a phylum of mostly sessile aquatic animals , ranging from 0.1 to 7 millimetres (0.004 to 0.3 in) long. Mature individuals are goblet -shaped, on relatively long stalks. They have a "crown" of solid tentacles whose cilia generate water currents that draw food particles towards
114-403: A "crown" of tentacles whose cilia generate water currents that draw food particles towards the mouth. However, they have different feeding mechanisms and internal anatomy, and bryozoans undergo a metamorphosis from larva to adult that destroys most of the larval tissues; their colonies also have a founder zooid which is different from its "daughters". The body of a mature entoproct zooid has
171-458: A certain degree of evolutionary relatedness (the phylogenetic definition). Attempting to define a level of the Linnean hierarchy without referring to (evolutionary) relatedness is unsatisfactory, but a phenetic definition is useful when addressing questions of a morphological nature—such as how successful different body plans were. The most important objective measure in the above definitions
228-407: A character unique to a sub-set of the crown group. Furthermore, organisms in the stem group of a phylum can possess the "body plan" of the phylum without all the characteristics necessary to fall within it. This weakens the idea that each of the phyla represents a distinct body plan. A classification using this definition may be strongly affected by the chance survival of rare groups, which can make
285-579: A clade Tetraneuralia , together with molluscs. "Entoprocta", coined in 1870, means " anus inside". The alternative name "Kamptozoa", meaning "bent" or "curved" animals, was assigned in 1929. Some authors use "Entoprocta", while others prefer "Kamptozoa". Most species are colonial, and their members are known as "zooids", since they are not fully independent animals. Zooids are typically 1 millimetre (0.039 in) long but range from 0.1 to 7 millimetres (0.004 to 0.3 in) long. Entoprocts are superficially like bryozoans (ectoprocts), as both groups have
342-431: A few species are found in the deep ocean. Some species of nudibranchs ("sea slugs"), particularly those of the genus Trapania , as well as turbellarian flatworms , prey on entoprocts. Small colonies of the freshwater entoproct Urnatella gracilis have been found living on the aquatic larvae of the dobsonfly Corydalus cornutus . The ectoprocts gain a means of dispersal, protection from predators and possibly
399-404: A goblet-like structure with a calyx mounted on a relatively long stalk that attaches to a surface. The rim of the calyx bears a "crown" of 8 to 30 solid tentacles, which are extensions of the body wall. The base of the "crown" of tentacles is surrounded by a membrane that partially covers the tentacles when they retract. The mouth and anus lie on opposite sides of the atrium (space enclosed by
456-602: A group containing Viridiplantae and the algal Rhodophyta and Glaucophyta divisions. The definition and classification of plants at the division level also varies from source to source, and has changed progressively in recent years. Thus some sources place horsetails in division Arthrophyta and ferns in division Monilophyta, while others place them both in Monilophyta, as shown below. The division Pinophyta may be used for all gymnosperms (i.e. including cycads, ginkgos and gnetophytes), or for conifers alone as below. Since
513-408: A network of stolons encrusting the surface to which the colony is attached; straight stalks joined to the stolons by bulky sockets with transverse bands of wrinkles; overall size and proportions similar to that of modern species of Barentsia . Another species, Cotyledion tylodes , first described in 1999, was larger than extant entoprocts, reaching 8–56 mm in height, and unlike modern species,
570-403: A pair of protonephridia , and a large, cilia-bearing foot at the bottom. After settling, the foot and frontal tuft attach to the surface. Larvae of most species undergo a complex metamorphosis , and the internal organs may rotate by up to 180°, so that the mouth and anus both point upwards. All species can produce clones by budding . Colonial species produce new zooids from the stolon or from
627-400: A phylum based on body plan has been proposed by paleontologists Graham Budd and Sören Jensen (as Haeckel had done a century earlier). The definition was posited because extinct organisms are hardest to classify: they can be offshoots that diverged from a phylum's line before the characters that define the modern phylum were all acquired. By Budd and Jensen's definition, a phylum is defined by
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#1732782390254684-471: A phylum much more diverse than it would be otherwise. Total numbers are estimates; figures from different authors vary wildly, not least because some are based on described species, some on extrapolations to numbers of undescribed species. For instance, around 25,000–27,000 species of nematodes have been described, while published estimates of the total number of nematode species include 10,000–20,000; 500,000; 10 million; and 100 million. The kingdom Plantae
741-706: A phylum, other phylum-level ranks appear, such as the case of Bacillariophyta (diatoms) within Ochrophyta . These differences became irrelevant after the adoption of a cladistic approach by the ISP, where taxonomic ranks are excluded from the classifications after being considered superfluous and unstable. Many authors prefer this usage, which lead to the Chromista-Protozoa scheme becoming obsolete. Currently there are 40 bacterial phyla (not including " Cyanobacteria ") that have been validly published according to
798-533: A round cross-section. In 1992 J.A. Todd and P.D. Taylor concluded that Dinomischus was not an entoproct, because it did not have the typical rounded, flexible tentacles, and the fossils showed no other features that clearly resembled those of entoprocts. In their opinion, the earliest fossil entoprocts were specimens they found from Late Jurassic rocks in England. These resemble the modern colonial genus Barentsia in many ways, including: upright zooids linked by
855-457: A sessile animal with calyx, stalk and holdfast, found in Canada 's Burgess Shale , which was formed about 505 million years ago . Conway Morris regarded this animal as the earliest known entoproct, since its mouth and anus lay inside a ring of structures above the calyx, but noted that these structures were flat and rather stiff, while the tentacles of modern entoprocts are flexible and have
912-401: A set of characters shared by all its living representatives. This approach brings some small problems—for instance, ancestral characters common to most members of a phylum may have been lost by some members. Also, this definition is based on an arbitrary point of time: the present. However, as it is character based, it is easy to apply to the fossil record. A greater problem is that it relies on
969-463: A similar epithelium, the gastrodermis , which forms a boundary with the epidermis at the mouth. Sponges have no epithelium, and therefore no epidermis or gastrodermis. The epidermis of a more complex invertebrate is just one layer deep, and may be protected by a non-cellular cuticle . The epidermis of a higher vertebrate has many layers, and the outer layers are reinforced with keratin and then die. This animal anatomy –related article
1026-407: A single layer of cells, each of which bears multiple cilia ("hairs") and microvilli (tiny "pleats") that penetrate through the cuticle. The stolons and stalks of colonial species have thicker cuticles, stiffened with chitin . There is no coelom (internal fluid-filled cavity lined with peritoneum ) and the other internal organs are embedded in connective tissue that lies between the stomach and
1083-479: A source of water that is rich in oxygen and nutrients, as colonies often live next to the gills of the larval flies. In the White Sea , the non-colonial entoproct Loxosomella nordgaardi prefers to live attached to bryozoan (ectoproct) colonies, mainly on the edges of colonies or in the "chimneys", gaps by which large bryozoan colonies expel water from which they have sieved food. Observation suggests that both
1140-403: A specimen belongs to a species that already occurs in the same area or is an invader , possibly as a result of human activities. Phylum (biology) In biology , a phylum ( / ˈ f aɪ l əm / ; pl. : phyla ) is a level of classification or taxonomic rank below kingdom and above class . Traditionally, in botany the term division has been used instead of phylum, although
1197-401: A subjective decision about which groups of organisms should be considered as phyla. The approach is useful because it makes it easy to classify extinct organisms as " stem groups " to the phyla with which they bear the most resemblance, based only on the taxonomically important similarities. However, proving that a fossil belongs to the crown group of a phylum is difficult, as it must display
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#17327823902541254-470: A surface. In solitary species, the stalk ends in a muscular sucker, or a flexible foot, or is cemented to a surface. The stalk is muscular and produces a characteristic nodding motion. In some species it is segmented . Some solitary species can move, either by creeping on the muscular foot or by somersaulting . The body wall consists of the epidermis and an external cuticle , which consists mainly of criss-cross collagen fibers. The epidermis contains only
1311-474: Is a paraphyletic taxon, which is less acceptable to present-day biologists than in the past. Proposals have been made to divide it among several new kingdoms, such as Protozoa and Chromista in the Cavalier-Smith system . Protist taxonomy has long been unstable, with different approaches and definitions resulting in many competing classification schemes. Many of the phyla listed below are used by
1368-402: Is a gap in the band nearest the anus. A separate band of cilia grows along a groove that runs close to the inner side of the base of the "crown", with a narrow extension up the inner surface of each tentacle. The cilia on the sides of the tentacles create a current that flows into the "crown" at the bases of the tentacles and exits above the center of the "crown". These cilia pass food particles to
1425-542: Is carried out by the same bands of cilia that generate the current; trochozoan larvae also use downstream collecting, but use a separate set of cilia to trap food particles. In addition, glands in the tentacles secrete sticky threads that capture large particles. A non-colonial species reported from around the Antarctic Peninsula in 1993 has cells that superficially resemble the cnidocytes of cnidaria , and fire sticky threads. These unusual cells lie around
1482-405: Is defined in various ways by different biologists (see Current definitions of Plantae ). All definitions include the living embryophytes (land plants), to which may be added the two green algae divisions, Chlorophyta and Charophyta , to form the clade Viridiplantae . The table below follows the influential (though contentious) Cavalier-Smith system in equating "Plantae" with Archaeplastida ,
1539-481: Is generally included in kingdom Fungi, though its exact relations remain uncertain, and it is considered a protozoan by the International Society of Protistologists (see Protista , below). Molecular analysis of Zygomycota has found it to be polyphyletic (its members do not share an immediate ancestor), which is considered undesirable by many biologists. Accordingly, there is a proposal to abolish
1596-436: Is the "certain degree" that defines how different organisms need to be members of different phyla. The minimal requirement is that all organisms in a phylum should be clearly more closely related to one another than to any other group. Even this is problematic because the requirement depends on knowledge of organisms' relationships: as more data become available, particularly from molecular studies, we are better able to determine
1653-454: Is the aggregate of all species which have gradually evolved from one and the same common original form, as, for example, all vertebrates. We name this aggregate [a] Stamm [i.e., stock] ( Phylon )." In plant taxonomy , August W. Eichler (1883) classified plants into five groups named divisions, a term that remains in use today for groups of plants, algae and fungi. The definitions of zoological phyla have changed from their origins in
1710-579: The Bacteriological Code Currently there are 2 phyla that have been validly published according to the Bacteriological Code Other phyla that have been proposed, but not validly named, include: Epidermis (zoology) In zoology, the epidermis is an epithelium (sheet of cells ) that covers the body of a eumetazoan ( animal more complex than a sponge ). Eumetazoa have a cavity lined with
1767-565: The Catalogue of Life , and correspond to the Protozoa-Chromista scheme, with updates from the latest (2022) publication by Cavalier-Smith . Other phyla are used commonly by other authors, and are adapted from the system used by the International Society of Protistologists (ISP). Some of the descriptions are based on the 2019 revision of eukaryotes by the ISP. The number of protist phyla varies greatly from one classification to
Entoprocta - Misplaced Pages Continue
1824-519: 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 8 phyla. Current research in phylogenetics is uncovering the relationships among phyla within larger clades like Ecdysozoa and Embryophyta . The term phylum
1881-419: The trochophore type. The trochozoa also include molluscs , annelids , flatworms , nemertines and others. However, scientists disagree about which phylum is mostly closely related to enctoprocts within the trochozoans. An analysis in 2008 re-introduced the pre-1869 meaning of the term "Bryozoa", for a group in which entoprocts and ectoprocts are each other's closest relatives. All species are sessile. While
1938-405: The "crown" of tentacles), and both can be closed by sphincter muscles. The gut is U-shaped, curving down towards the base of the calyx, where it broadens to form the stomach. This is lined with a membrane consisting of a single layer of cells, each of which has multiple cilia . The stalks of colonial species arise from shared attachment plates or from a network of stolons , tubes that run across
1995-497: The Zygomycota phylum. Its members would be divided between phylum Glomeromycota and four new subphyla incertae sedis (of uncertain placement): Entomophthoromycotina , Kickxellomycotina , Mucoromycotina , and Zoopagomycotina . Kingdom Protista (or Protoctista) is included in the traditional five- or six-kingdom model, where it can be defined as containing all eukaryotes that are not plants, animals, or fungi. Protista
2052-471: The anus is outside the feeding organ. However, studies by one team in 2007 and 2008 argue for sinking Entoprocta into Bryozoa as a class , and resurrecting Ectoprocta as a name for the currently identified bryozoans. The consensus of studies from 1996 onwards has been that entoprocts are part of the Trochozoa , a protostome "superphylum" whose members are united in having as their most basic larval form
2109-407: The base of the "crown" of tentacles. The nervous system runs through the connective tissue and just below the epidermis, and is controlled by a pair of ganglia . Nerves run from these to the calyx, tentacles and stalk, and to sense organs in all these areas. A band of cells, each with multiple cilia, runs along the sides of the tentacles, connecting each tentacle to its neighbors, except that there
2166-470: The cilia on the inner surface of the tentacles, and the inner cilia produce a downward current that drives particles into and around the groove, and then to the mouth. Entoprocts generally use one or both of: ciliary sieving, in which one band of cilia creates the feeding current and another traps food particles (the " sieve "); and downstream collecting, in which food particles are trapped as they are about to exit past them. In entoprocts, downstream collecting
2223-423: The developing eggs. After hatching, the larvae swim for a short time and then settle on a surface. There they metamorphose , and the larval gut rotates by up to 180°, so that the mouth and anus face upwards. Both colonial and solitary species also reproduce by cloning — solitary species grow clones in the space between the tentacles and then release them when developed, while colonial ones produce new members from
2280-405: The entoprocts and the bryozoans benefit from the association: each enhances the water flow that the other needs for feeding; and the longer cilia of the entoprocts may help them to capture different food from that caught by the bryozoans, so that the animals do not compete for the same food. Entoprocts are small and have been little studied by zoologists. Hence it is difficult to determine whether
2337-405: The fertilized egg into a larva follows a typical spiralian pattern: the cells divide by spiral cleavage , and mesoderm develops from a specific cell labelled "4d" in the early embryo . There is no coelom at any stage. In some species the larva is a trochophore which is planktonic and feeds on floating food particles by using the two bands of cilia round its "equator" to sweep food into
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2394-507: The first publication of the APG system in 1998, which proposed a classification of angiosperms up to the level of orders , many sources have preferred to treat ranks higher than orders as informal clades. Where formal ranks have been provided, the traditional divisions listed below have been reduced to a very much lower level, e.g. subclasses . Wolf plants Hepatophyta Liver plants Coniferophyta Cone-bearing plant Phylum Microsporidia
2451-538: The great majority are marine, two species live in freshwater: Loxosomatoides sirindhornae , reported in 2004 in central Thailand , and Urnatella gracilis , found in all the continents except Antarctica . Colonial species are found in all the oceans, living on rocks, shells, algae and underwater buildings. The solitary species, which are marine, live on other animals that feed by producing water currents, such as sponges , ectoprocts and sessile annelids . The majority of species live no deeper than 50 meters, but
2508-482: The mouth, and both the mouth and anus lie inside the "crown". The superficially similar Bryozoa (Ectoprocta) have the anus outside a "crown" of hollow tentacles. Most families of entoprocts are colonial, and all but 2 of the 150 species are marine. A few solitary species can move slowly. Some species eject unfertilized ova into the water, while others keep their ova in brood chambers until they hatch, and some of these species use placenta -like organs to nourish
2565-400: The mouth, and may provide an additional means of capturing prey. The stomach and intestine are lined with microvilli , which are thought to absorb nutrients. The anus, which opens inside the "crown", ejects solid wastes into the outgoing current after the tentacles have filtered food out of the water; in some families it is raised on a cone above the level of the groove that conducts food to
2622-432: The mouth, which uses more cilia to drive them into the stomach, which uses further cilia to expel undigested remains through the anus. In some species of the genera Loxosomella and Loxosoma , the larva produces one or two buds that separate and form new individuals, while the trochophore disintegrates. However, most produce a larva with sensory tufts at the top and front, a pair of pigment-cup ocelli ("little eyes"),
2679-513: The mouth. Most species have a pair of protonephridia which extract soluble wastes from the internal fluids and eliminate them through pores near the mouth. However, the freshwater species Urnatella gracilis has multiple nephridia in the calyx and stalk. The zooids absorb oxygen and emit carbon dioxide by diffusion , which works well for small animals. Most species are simultaneous hermaphrodites , but some switch from male to female as they mature, while individuals of some species remain of
2736-411: The next. The Catalogue of Life includes Rhodophyta and Glaucophyta in kingdom Plantae, but other systems consider these phyla part of Protista. In addition, less popular classification schemes unite Ochrophyta and Pseudofungi under one phylum, Gyrista , and all alveolates except ciliates in one phylum Myzozoa , later lowered in rank and included in a paraphyletic phylum Miozoa . Even within
2793-539: The other hand, the highly parasitic phylum Mesozoa was divided into two phyla ( Orthonectida and Rhombozoa ) when it was discovered the Orthonectida are probably deuterostomes and the Rhombozoa protostomes . This changeability of phyla has led some biologists to call for the concept of a phylum to be abandoned in favour of placing taxa in clades without any formal ranking of group size. A definition of
2850-496: The phylum Bryozoa , because both groups were sessile animals that filter-fed by means of a "crown" of tentacles that bore cilia . However, from 1869 onwards, increasing awareness of differences, including the position of the entoproct anus inside the feeding structure and the difference in the early pattern of division of cells in their embryos , caused scientists to regard the two groups as separate phyla . "Bryozoa" then became just an alternative name for ectoprocts, in which
2907-475: The relationships between groups. So phyla can be merged or split if it becomes apparent that they are related to one another or not. For example, the bearded worms were described as a new phylum (the Pogonophora) in the middle of the 20th century, but molecular work almost half a century later found them to be a group of annelids , so the phyla were merged (the bearded worms are now an annelid family ). On
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#17327823902542964-484: The same sex all their lives. Individuals have one or two pairs of gonads , placed between the atrium and stomach, and opening into a single gonopore in the atrium. The eggs are thought to be fertilized in the ovaries . Most species release eggs that hatch into planktonic larvae , but a few brood their eggs in the gonopore. Those that brood small eggs nourish them by a placenta -like organ, while larvae of species with larger eggs live on stored yolk . The development of
3021-399: The six Linnaean classes and the four embranchements of Georges Cuvier . Informally, phyla can be thought of as groupings of organisms based on general specialization of body plan . At its most basic, a phylum can be defined in two ways: as a group of organisms with a certain degree of morphological or developmental similarity (the phenetic definition), or a group of organisms with
3078-492: The stalks or from corridor-like stolons . Fossils of entoprocts are very rare, and the earliest specimens that have been identified with confidence date from the Late Jurassic . Most studies from 1996 onwards have regarded entoprocts as members of the Trochozoa , which also includes molluscs and annelids . However, a study in 2008 concluded that entoprocts are closely related to bryozoans. Other studies place them in
3135-407: The stalks, and can form large colonies in this way. In solitary species, clones form on the floor of the atrium, and are released when their organs are developed. The phylum consists of about 150 recognized species, grouped into 4 families : Since entoprocts are small and soft-bodied, fossils have been extremely rare. In 1977, Simon Conway Morris provided the first description of Dinomischus ,
3192-479: Was "armored" with sclerites, scale-like structures. C. tylodes did have a similar sessile lifestyle to modern entoprocts. The identified fossils of C. tylodes were found in 520-million-year-old rocks from southern China. This places early entoprocts in the period of the Cambrian explosion . When entoprocts were discovered in the nineteenth century, they and bryozoans (ectoprocts) were regarded as classes within
3249-468: Was coined in 1866 by Ernst Haeckel from the Greek phylon ( φῦλον , "race, stock"), related to phyle ( φυλή , "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"): "perhaps such a real and completely self-contained unity
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