28-466: 2, see text Perkinsidae is a family of alveolates in the phylum Perkinsozoa , a sister group to the dinoflagellates . It includes Perkinsus species, which are parasitic protozoans , some of which cause disease and mass mortality in wild and farmed molluscs such as oysters . There are two genera : Perkinsidae possess plastids which do not contain DNA. This alveolate -related article
56-406: A dinoflagellate . It is known as a prevalent pathogen of oysters , causing massive mortality in oyster populations. The disease it causes is known as dermo or perkinsosis, and is characterized by the degradation of oyster tissues. The genome of this species has been sequenced . The species originally was named Dermocystidium marinum by Mackin, Owen and Collier in 1950. P. marinus
84-406: A plastid . Chromerids, apicomplexans, and peridinin dinoflagellates have retained this organelle . Going one step even further back, the chromerids, the peridinin dinoflagellates and the heterokont algae have been argued to possess a monophyletic plastid lineage in common, i.e. acquired their plastids from a red alga , and so it seems likely that the common ancestor of alveolates and heterokonts
112-475: A model alveolate, having been genetically studied in great depth over the longest period of any alveolate lineage. They are unusual among eukaryotes in that reproduction involves a micronucleus and a macronucleus . Their reproduction is easily studied in the lab, and made them a model eukaryote historically. Being entirely predatory and lacking any remnant plastid, their development as a phylum illustrates how predation and autotrophy are in dynamic balance and that
140-589: A taxon now split because each has a distinctive organization or ultrastructural identity . The Acavomonidia are closer to the dinoflagellate/perkinsid group than the Colponemidia are. As such, the informal term "colponemids", as it stands currently, covers two non-sister groups within Alveolata: the Acavomonidia and the Colponemidia. The Apicomplexa and dinoflagellates may be more closely related to each other than to
168-461: Is a protozoan of the protist superphylum Alveolata, the alveolates . Its phylum, Perkinsozoa, is a relatively new taxon positioned between the dinoflagellates and the Apicomplexa , and is probably more closely related to the former. P. marinus is the type species of the genus Perkinsus , which was erected in 1978. When first identified in 1950, it was mistaken for a fungus . The protist
196-502: Is a stub . You can help Misplaced Pages by expanding it . Alveolata The alveolates (meaning "pitted like a honeycomb") are a group of protists , considered a major clade and superphylum within Eukarya . They are currently grouped with the stramenopiles and Rhizaria among the protists with tubulocristate mitochondria into the SAR supergroup . The most notable shared characteristic
224-405: Is about 2 to 4 μm long. The zoospore has two flagella , which it uses to swim in its marine habitat. It is ingested by its mollusc host , which is often an oyster of the genus Crassostrea . It then becomes a trophozoite , which proliferates in the tissues of the host. P. marinus often infests the hemocytes , cells in the blood of the host, analogous to malaria in vertebrates. It
252-457: Is also often seen in the cells of the intestine , connective tissues , digestive glands, and gills . Inside the cell, the trophozoite produces a vacuole that displaces the cell nucleus . The infested cell is referred to as a signet ring cell , because it is spherical and filled with the rounded vacuole, and resembles a signet ring . The mature trophozoite undergoes binary fission and up to 16 immature trophozoites are produced. These stay in
280-407: Is the presence of cortical (near the surface) alveoli (sacs) . These are flattened vesicles (sacs) arranged as a layer just under the membrane and supporting it, typically contributing to a flexible pellicle (thin skin). In armored dinoflagellates they may contain stiff plates. Alveolates have mitochondria with tubular cristae ( invaginations ), and cells often have pore-like intrusions through
308-769: The Cercozoa . The ellobiopsids are of uncertain relation within the alveolates. Silberman et al 2004 establish that the Thalassomyces genus of ellobiopsids are alveolates using phylogenetic analysis, however as of 2016 no more certainty exists on their place. In 2017, Thomas Cavalier-Smith described the phylogeny of the Alveolata as follows: Heterotrichea Karyorelictea Desmata Spirotrichia Colponemea Acavomonadea Apicomonada Sporozoa Dinoflagellata Perkinsea Alveolata Cavalier-Smith 1991 [Alveolatobiontes] The development of plastids among
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#1732870105046336-574: The ellobiopsids . In 2001, direct amplification of the rRNA gene in marine picoplankton samples revealed the presence of two novel alveolate lineages, called group I and II. Group I has no cultivated relatives, while group II is related to the dinoflagellate parasite Amoebophrya , which was classified until now in the Syndiniales dinoflagellate order. Some studies suggested the haplosporids , mostly parasites of marine invertebrates, might belong here, but they lack alveoli and are now placed among
364-594: The 1980s, and this was confirmed in the early 1990s by comparisons of ribosomal RNA sequences, most notably by Gajadhar et al . Cavalier-Smith introduced the formal name Alveolata in 1991, although at the time he considered the grouping to be a paraphyletic assemblage. Many biologists prefer the use of the colloquial name 'alveolate'. Alveolata include around nine major and minor groups. They are diverse in form, and are known to be related by various ultrastructural and genetic similarities: The Acavomonidia and Colponemidia were previously grouped together as colponemids,
392-487: The Chromerida and the heterokont algae acquired their plastids from a red alga with evidence of a common origin of this organelle in all these four clades. A Bayesian estimate places the evolution of the alveolate group at ~ 850 million years ago . The Alveolata consist of Myzozoa , Ciliates , and Colponemids. In other words, the term Myzozoa, meaning "to siphon the contents from prey", may be applied informally to
420-825: The North American coast from New Brunswick to Florida to the Yucatán Peninsula of Mexico . Dermo epizootic outbreaks occurred in the Gulf of Mexico in the 1940s. Periodic outbreaks in the Chesapeake Bay have caused extensive oyster mortality. Significant disease has occurred in Delaware Bay , Long Island Sound , and other parts of the coast of the northeastern United States. Oyster farming operations have been disrupted in some areas, particularly in Mexico. The prevalence of
448-466: The alveolates is intriguing. Cavalier-Smith proposed the alveolates developed from a chloroplast-containing ancestor, which also gave rise to the Chromista (the chromalveolate hypothesis). Other researchers have speculated that the alveolates originally lacked plastids and possibly the dinoflagellates and Apicomplexa acquired them separately. However, it now appears that the alveolates, the dinoflagellates,
476-403: The balance can swing one way or other at the point of origin of a new phylum from mixotrophic ancestors, causing one ability to be lost. Few algae have been studied for epigenetics . Those for which epigenetic data are available include some algal alveolates. Perkinsus marinus Perkinsus marinus is a species of alveolate belonging to the phylum Perkinsozoa . It is similar to
504-437: The basis that apicomplexans possess a plastid surrounded by four membranes, and that peridinin dinoflagellates possess a plastid surrounded by three membranes, Petersen et al. have been unable to rule out that the shared stramenopile-alveolate plastid could have been recycled multiple times in the alveolate phylum, the source being stramenopile-alveolate donors, through the mechanism of ingestion and endosymbiosis . Ciliates are
532-696: The cell surface. The group contains free-living and parasitic organisms, predatory flagellates , and photosynthetic organisms. Almost all sequenced mitochondrial genomes of ciliates and apicomplexa are linear. The mitochondria almost all carry mtDNA of their own but with greatly reduced genome sizes. Exceptions are Cryptosporidium which are left with only a mitosome , the circular mitochondrial genomes of Acavomonas and Babesia microti , and Toxoplasma ' s highly fragmented mitochondrial genome, consisting of 21 sequence blocks which recombine to produce longer segments. The relationship of apicomplexa, dinoflagellates and ciliates had been suggested during
560-620: The ciliates. Both have plastids , and most share a bundle or cone of microtubules at the top of the cell. In apicomplexans this forms part of a complex used to enter host cells, while in some colorless dinoflagellates it forms a peduncle used to ingest prey. Various other genera are closely related to these two groups, mostly flagellates with a similar apical structure. These include free-living members in Oxyrrhis and Colponema , and parasites in Perkinsus , Parvilucifera , Rastrimonas and
588-431: The common ancestor of the subset of alveolates that are neither ciliates nor colponemids. Predation upon algae is an important driver in alveolate evolution, as it can provide sources for endosymbiosis of novel plastids. The term Myzozoa is therefore a handy concept for tracking the history of the alveolate phylum. The ancestors of the alveolate group may have been photosynthetic. The ancestral alveolate probably possessed
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#1732870105046616-628: The host animal and infest its tissues, or are released into the water in the feces or from a dead host. Trophozoites in the water mature and release flagellated zoospores. The most economically important host is the eastern oyster ( Crassostrea virginica ). The parasite is also common in C. corteziensis , and the species C. rhizophorae , C. gasar , and C. brasiliana are probably susceptible. Magallana gigas and M. ariakensis are experimentally susceptible, but may be more resistant. Certain clams such as Mya arenaria and Macoma balthica can be infected in experimental situations. In
644-541: The host, or into its bloodstream. There, they infest more cells or are excreted or released when the host dies and disintegrates. The infected oyster becomes stressed, its tissues are pale in color, its gamete production is retarded, its growth slows, it becomes emaciated , its mantle shrivels and pulls away from the shell, and it may develop pockets of pus -like fluid. Lysis of tissues and blockage of blood vessels causes fatality, but many oysters can persist up to 3 years with active infections. The protist occurs along
672-405: The laboratory, the sea snail Boonea impressa can be infected and then pass the parasite to an oyster host. Perkinsosis or "dermo" is the disease condition of the oyster. The name "dermo" was coined when the protist was named Dermocystidium marinum , and it is still commonly used. Infested cells are destroyed by the reproducing protist, and many trophozoites are released into the tissues of
700-421: The protist and the disease are influenced by environmental factors such as temperature, salinity , and food availability to the hosts. Oysters exposed to environmental pollutants such as N -Nitrosodimethylamine , and tributyltins experience more severe disease. At higher temperatures, the chemical defenses of the oyster, particularly its lysozymes , are reduced; infections are more common and more severe in
728-570: The summer. Warmer winter ocean temperatures also promote outbreaks. While laboratory studies of certain antibiotics have been promising, no methods of eradication are effective, so prevention is important. Oysters from populations or farms that have experienced disease should not be moved to areas without infestations, because the protist is easily introduced and transmitted. In aquaculture , efforts to locate and breed more resistant strains of oysters are ongoing. Infested seed oysters should not be planted in oyster beds, and in disease-ridden areas,
756-459: Was also photosynthetic. In one school of thought the common ancestor of the dinoflagellates , apicomplexans , Colpodella , Chromerida , and Voromonas was a myzocytotic predator with two heterodynamic flagella , micropores , trichocysts , rhoptries , micronemes , a polar ring and a coiled open sided conoid . While the common ancestor of alveolates may also have possessed some of these characteristics, it has been argued that Myzocytosis
784-412: Was not one of these characteristics, as ciliates ingest prey by a different mechanism. An ongoing debate concerns the number of membranes surrounding the plastid across apicomplexans and certain dinoflagellates, and the origin of these membranes. This ultrastructural character can be used to group organisms and if the character is in common, it can imply that phyla had a common photosynthetic ancestor. On
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