101-513: See text Symbiodiniaceae is a family of marine dinoflagellates notable for their symbiotic associations with reef-building corals , sea anemones , jellyfish , marine sponges , giant clams , acoel flatworms , and other marine invertebrates. Symbiotic Symbiodiniaceae are sometimes colloquially referred to as Zooxanthellae , though the latter term can be interpreted to include other families of symbiotic algae as well. While many Symbiodiniaceae species are endosymbionts, others are free living in
202-412: A biased random walk , with runs and tumbles brought about by rotating its flagellum counterclockwise and clockwise , respectively. The two directions of rotation are not identical (with respect to flagellum movement) and are selected by a molecular switch. Clockwise rotation is called the traction mode with the body following the flagella. Counterclockwise rotation is called the thruster mode with
303-401: A cyst . Different types of dinoflagellate cysts are mainly defined based on morphological (number and type of layers in the cell wall) and functional (long- or short-term endurance) differences. These characteristics were initially thought to clearly distinguish pellicle (thin-walled) cysts from resting (double-walled) dinoflagellate cysts. The former were considered short-term (temporal) and
404-477: A haplontic life cycle , with the possible exception of Noctiluca and its relatives. The life cycle usually involves asexual reproduction by means of mitosis, either through desmoschisis or eleuteroschisis . More complex life cycles occur, more particularly with parasitic dinoflagellates. Sexual reproduction also occurs, though this mode of reproduction is only known in a small percentage of dinoflagellates. This takes place by fusion of two individuals to form
505-560: A zygote , which may remain mobile in typical dinoflagellate fashion and is then called a planozygote. This zygote may later form a resting stage or hypnozygote , which is called a dinoflagellate cyst or dinocyst . After (or before) germination of the cyst, the hatchling undergoes meiosis to produce new haploid cells . Dinoflagellates appear to be capable of carrying out several DNA repair processes that can deal with different types of DNA damage . The life cycle of many dinoflagellates includes at least one nonflagellated benthic stage as
606-484: A T3SS. However, it has also been suggested that the flagellum may have evolved first or the two structures evolved in parallel. Early single-cell organisms' need for motility (mobility) support that the more mobile flagella would be selected by evolution first, but the T3SS evolving from the flagellum can be seen as 'reductive evolution', and receives no topological support from the phylogenetic trees. The hypothesis that
707-401: A dinokaryon are classified under Syndiniales . Although classified as eukaryotes , the dinoflagellate nuclei are not characteristically eukaryotic, as some of them lack histones and nucleosomes , and maintain continually condensed chromosomes during mitosis . The dinoflagellate nucleus was termed 'mesokaryotic' by Dodge (1966), due to its possession of intermediate characteristics between
808-401: A lack of diversity may occur in a bloom is through a reduction in predation and a decreased competition. The first may be achieved by having predators reject the dinoflagellate, by, for example, decreasing the amount of food it can eat. This additionally helps prevent a future increase in predation pressure by causing predators that reject it to lack the energy to breed. A species can then inhibit
909-487: A loss rather than being a primitive condition. The loss of cilia occurred in red algae , some green algae ( Zygnematophyceae ), the gymnosperms except cycads and Ginkgo , angiosperms , pennate diatoms , some apicomplexans , some amoebozoans , in the sperm of some metazoans , and in fungi (except chytrids ). A number of terms related to flagella or cilia are used to characterize eukaryotes. According to surface structures present, flagella may be: According to
1010-458: A novel, dominant family of nuclear proteins that appear to be of viral origin, thus are called Dinoflagellate viral nucleoproteins (DVNPs) which are highly basic, bind DNA with similar affinity to histones, and occur in multiple posttranslationally modified forms. Dinoflagellate nuclei remain condensed throughout interphase rather than just during mitosis , which is closed and involves a uniquely extranuclear mitotic spindle . This sort of nucleus
1111-510: A plastid derived from secondary endosymbiosis of red algae, however dinoflagellates with plastids derived from green algae and tertiary endosymbiosis of diatoms have also been discovered. Similar to other photosynthetic organisms, dinoflagellates contain chlorophylls a and c2 and the carotenoid beta-carotene. Dinoflagellates also produce the xanthophylls including peridinin , dinoxanthin , and diadinoxanthin . These pigments give many dinoflagellates their typical golden brown color. However,
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#17328013953691212-573: A potent neurotoxin that immobilizes its prey upon contact. When K. arminger are present in large enough quantities, they are able to cull whole populations of its copepods prey. The feeding mechanisms of the oceanic dinoflagellates remain unknown, although pseudopodial extensions were observed in Podolampas bipes . Dinoflagellate blooms are generally unpredictable, short, with low species diversity, and with little species succession. The low species diversity can be due to multiple factors. One way
1313-852: A result of the abundant nutrients in the water. Although the resulting red waves are an interesting visual phenomenon, they contain toxins that not only affect all marine life in the ocean, but the people who consume them as well. A specific carrier is shellfish . This can introduce both nonfatal and fatal illnesses. One such poison is saxitoxin , a powerful paralytic neurotoxin . Human inputs of phosphate further encourage these red tides, so strong interest exists in learning more about dinoflagellates, from both medical and economic perspectives. Dinoflagellates are known to be particularly capable of scavenging dissolved organic phosphorus for P-nutrient, several HAS species have been found to be highly versatile and mechanistically diversified in utilizing different types of DOPs. The ecology of harmful algal blooms
1414-484: A speed, a bacterium would take about 245 days to cover 1 km; although that may seem slow, the perspective changes when the concept of scale is introduced. In comparison to macroscopic life forms, it is very fast indeed when expressed in terms of number of body lengths per second. A cheetah, for example, only achieves about 25 body lengths per second. Through use of their flagella, bacteria are able to move rapidly towards attractants and away from repellents, by means of
1515-531: A total of 2,294 living dinoflagellate species, which includes marine, freshwater, and parasitic dinoflagellates. A rapid accumulation of certain dinoflagellates can result in a visible coloration of the water, colloquially known as red tide (a harmful algal bloom ), which can cause shellfish poisoning if humans eat contaminated shellfish. Some dinoflagellates also exhibit bioluminescence , primarily emitting blue-green light, which may be visible in oceanic areas under certain conditions. The term "dinoflagellate"
1616-411: A turning force. The longitudinal flagellum is relatively conventional in appearance, with few or no hairs. It beats with only one or two periods to its wave. The flagella lie in surface grooves: the transverse one in the cingulum and the longitudinal one in the sulcus, although its distal portion projects freely behind the cell. In dinoflagellate species with desmokont flagellation (e.g., Prorocentrum ),
1717-425: Is 19–20 μm long. A nonfunctioning centriole lies adjacent to the kinetosome . Nine interconnected props attach the kinetosome to the plasmalemma , and a terminal plate is present in the transitional zone. An inner ring-like structure attached to the tubules of the flagellar doublets within the transitional zone has been observed in transverse section. [REDACTED] This article incorporates text from
1818-669: Is a combination of the Greek dinos and the Latin flagellum . Dinos means "whirling" and signifies the distinctive way in which dinoflagellates were observed to swim. Flagellum means "whip" and this refers to their flagella . In 1753, the first modern dinoflagellates were described by Henry Baker as "Animalcules which cause the Sparkling Light in Sea Water", and named by Otto Friedrich Müller in 1773. The term derives from
1919-416: Is a hair-like appendage that protrudes from certain plant and animal sperm cells , from fungal spores ( zoospores ), and from a wide range of microorganisms to provide motility . Many protists with flagella are known as flagellates . A microorganism may have from one to many flagella. A gram-negative bacterium Helicobacter pylori , for example, uses its flagella to propel itself through
2020-448: Is called a red tide , from the color the bloom imparts to the water. Some colorless dinoflagellates may also form toxic blooms, such as Pfiesteria . Some dinoflagellate blooms are not dangerous. Bluish flickers visible in ocean water at night often come from blooms of bioluminescent dinoflagellates, which emit short flashes of light when disturbed. A red tide occurs because dinoflagellates are able to reproduce rapidly and copiously as
2121-412: Is extensively studied. At night, water can have an appearance of sparkling light due to the bioluminescence of dinoflagellates. More than 18 genera of dinoflagellates are bioluminescent, and the majority of them emit a blue-green light. These species contain scintillons , individual cytoplasmic bodies (about 0.5 μm in diameter) distributed mainly in the cortical region of the cell, outpockets of
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#17328013953692222-1038: Is found either in specialized cells of multicellular organisms (e.g., the choanocytes of sponges , or the ciliated epithelia of metazoans ), as in ciliates and many eukaryotes with a "flagellate condition" (or "monadoid level of organization ", see Flagellata , an artificial group). Flagellated lifecycle stages are found in many groups, e.g., many green algae (zoospores and male gametes), bryophytes (male gametes), pteridophytes (male gametes), some gymnosperms ( cycads and Ginkgo , as male gametes), centric diatoms (male gametes), brown algae (zoospores and gametes), oomycetes (assexual zoospores and gametes), hyphochytrids (zoospores), labyrinthulomycetes (zoospores), some apicomplexans (gametes), some radiolarians (probably gametes), foraminiferans (gametes), plasmodiophoromycetes (zoospores and gametes), myxogastrids (zoospores), metazoans (male gametes), and chytrid fungi (zoospores and gametes). Flagella or cilia are completely absent in some groups, probably due to
2323-443: Is made up of protein subunits of flagellin . Its shape is a 20- nanometer -thick hollow tube. It is helical and has a sharp bend just outside the outer membrane; this "hook" allows the axis of the helix to point directly away from the cell. A shaft runs between the hook and the basal body , passing through protein rings in the cell's membrane that act as bearings. Gram-positive organisms have two of these basal body rings, one in
2424-427: Is pH sensitive. When the pH drops, luciferase changes its shape, allowing luciferin, more specifically tetrapyrrole, to bind. Dinoflagellates can use bioluminescence as a defense mechanism. They can startle their predators by their flashing light or they can ward off potential predators by an indirect effect such as the "burglar alarm". The bioluminescence attracts attention to the dinoflagellate and its attacker, making
2525-422: Is still common (e.g., Andersen et al., 1991; Leadbeater et al., 2000). The core of a eukaryotic flagellum, known as the axoneme is a bundle of nine fused pairs of microtubules known as doublets surrounding two central single microtubules ( singlets ). This 9+2 axoneme is characteristic of the eukaryotic flagellum. At the base of a eukaryotic flagellum is a basal body , "blepharoplast" or kinetosome, which
2626-793: Is sufficient for nutrition, are classified as amphitrophic. If both forms are required, the organisms are mixotrophic sensu stricto . Some free-living dinoflagellates do not have chloroplasts, but host a phototrophic endosymbiont. A few dinoflagellates may use alien chloroplasts (cleptochloroplasts), obtained from food ( kleptoplasty ). Some dinoflagellates may feed on other organisms as predators or parasites. Food inclusions contain bacteria, bluegreen algae, diatoms, ciliates, and other dinoflagellates. Mechanisms of capture and ingestion in dinoflagellates are quite diverse. Several dinoflagellates, both thecate (e.g. Ceratium hirundinella , Peridinium globulus ) and nonthecate (e.g. Oxyrrhis marina , Gymnodinium sp. and Kofoidinium spp. ), draw prey to
2727-503: Is suited to locomotion of microscopic organisms; these organisms operate at a low Reynolds number , where the viscosity of the surrounding water is much more important than its mass or inertia. The rotational speed of flagella varies in response to the intensity of the proton-motive force, thereby permitting certain forms of speed control, and also permitting some types of bacteria to attain remarkable speeds in proportion to their size; some achieve roughly 60 cell lengths per second. At such
2828-399: Is the microtubule organizing center for flagellar microtubules and is about 500 nanometers long. Basal bodies are structurally identical to centrioles . The flagellum is encased within the cell's plasma membrane , so that the interior of the flagellum is accessible to the cell's cytoplasm . Besides the axoneme and basal body, relatively constant in morphology, other internal structures of
2929-537: The International Code of Botanical Nomenclature (ICBN, now renamed as ICN) and the International Code of Zoological Nomenclature (ICZN). About half of living dinoflagellate species are autotrophs possessing chloroplasts and half are nonphotosynthesising heterotrophs. The peridinin dinoflagellates, named after their peridinin plastids, appear to be ancestral for the dinoflagellate lineage. Almost half of all known species have chloroplasts, which are either
3030-489: The Symbiodinium genus. There are eleven accepted genera in this family: This dinoflagellate -related article is a stub . You can help Misplaced Pages by expanding it . Dinoflagellate The dinoflagellates (from Ancient Greek δῖνος ( dînos ) 'whirling' and Latin flagellum 'whip, scourge') are a monophyletic group of single-celled eukaryotes constituting
3131-603: The flagellate order Dinoflagellida. Botanists treated them as a division of algae, named Pyrrophyta or Pyrrhophyta ("fire algae"; Greek pyrr(h)os , fire) after the bioluminescent forms, or Dinophyta . At various times, the cryptomonads , ebriids , and ellobiopsids have been included here, but only the last are now considered close relatives. Dinoflagellates have a known ability to transform from noncyst to cyst-forming strategies, which makes recreating their evolutionary history extremely difficult. Dinoflagellates are unicellular and possess two dissimilar flagella arising from
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3232-429: The peptidoglycan layer and one in the plasma membrane . Gram-negative organisms have four such rings: the L ring associates with the lipopolysaccharides , the P ring associates with peptidoglycan layer, the M ring is embedded in the plasma membrane , and the S ring is directly attached to the cytoplasm . The filament ends with a capping protein. The flagellar filament is the long, helical screw that propels
3333-436: The periplasmic space as shown by breaking the outer-membrane and also by electron cryotomography microscopy. The rotation of the filaments relative to the cell body causes the entire bacterium to move forward in a corkscrew-like motion, even through material viscous enough to prevent the passage of normally flagellated bacteria. In certain large forms of Selenomonas , more than 30 individual flagella are organized outside
3434-455: The theca or lorica , as opposed to athecate ("nude") dinoflagellates. These occur in various shapes and arrangements, depending on the species and sometimes on the stage of the dinoflagellate. Conventionally, the term tabulation has been used to refer to this arrangement of thecal plates . The plate configuration can be denoted with the plate formula or tabulation formula. Fibrous extrusomes are also found in many forms. A transverse groove,
3535-468: The 350 described freshwater species and a little more than 10% of the known marine species. Dinoflagellates are alveolates possessing two flagella , the ancestral condition of bikonts . About 1,555 species of free-living marine dinoflagellates are currently described. Another estimate suggests about 2,000 living species, of which more than 1,700 are marine (free-living, as well as benthic) and about 220 are from fresh water. The latest estimates suggest
3636-483: The Greek word δῖνος ( dînos ), meaning whirling, and Latin flagellum , a diminutive term for a whip or scourge. In the 1830s, the German microscopist Christian Gottfried Ehrenberg examined many water and plankton samples and proposed several dinoflagellate genera that are still used today including Peridinium, Prorocentrum , and Dinophysis . These same dinoflagellates were first defined by Otto Bütschli in 1885 as
3737-544: The United States, Central Florida is home to the Indian River Lagoon which is abundant with dinoflagellates in the summer and bioluminescent ctenophore in the winter. Dinoflagellates produce characteristic lipids and sterols. One of these sterols is typical of dinoflagellates and is called dinosterol . Dinoflagellate theca can sink rapidly to the seafloor in marine snow . Dinoflagellates have
3838-451: The ability of the dinoflagellate to prey upon larger copepods. Toxic strains of K. veneficum produce karlotoxin that kills predators who ingest them, thus reducing predatory populations and allowing blooms of both toxic and non-toxic strains of K. veneficum . Further, the production of karlotoxin enhances the predatory ability of K. veneficum by immobilizing its larger prey. K. arminger are more inclined to prey upon copepods by releasing
3939-407: The addition of N-linked glycans which are necessary for proper assembly or function. Discoveries in the 1990s revealed numerous detailed differences between the archaeal and bacterial flagella. These include: These differences support the theory that the bacterial flagella and archaella are a classic case of biological analogy , or convergent evolution , rather than homology . Research into
4040-455: The advantages of recombination and sexuality, such that in fungi, for example, complex combinations of haploid and diploid cycles have evolved that include asexual and sexual resting stages. However, in the general life cycle of cyst-producing dinoflagellates as outlined in the 1960s and 1970s, resting cysts were assumed to be the fate of sexuality, which itself was regarded as a response to stress or unfavorable conditions. Sexuality involves
4141-510: The bacterial flagella and the eukaryotic cilia and flagella, some authors attempted to replace the name of these two eukaryotic structures with " undulipodia " (e.g., all papers by Margulis since the 1970s) or "cilia" for both (e.g., Hülsmann, 1992; Adl et al., 2012; most papers of Cavalier-Smith ), preserving "flagella" for the bacterial structure. However, the discriminative usage of the terms "cilia" and "flagella" for eukaryotes adopted in this article (see § Flagella versus cilia below)
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4242-493: The bacterial flagellum share homologous proteins with the type three secretion system (T3SS) found in many gram-negative bacteria, hence one likely evolved from the other. Because the T3SS has a similar number of components as a flagellar apparatus (about 25 proteins), which one evolved first is difficult to determine. However, the flagellar system appears to involve more proteins overall, including various regulators and chaperones, hence it has been argued that flagella evolved from
4343-531: The bacterium when rotated by the motor, through the hook. In most bacteria that have been studied, including the gram-negative Escherichia coli , Salmonella typhimurium , Caulobacter crescentus , and Vibrio alginolyticus , the filament is made up of 11 protofilaments approximately parallel to the filament axis. Each protofilament is a series of tandem protein chains. However, Campylobacter jejuni has seven protofilaments. The basal body has several traits in common with some types of secretory pores , such as
4444-448: The basis of gross morphology and behavior. Both flagella and archaella consist of filaments extending outside the cell, and rotate to propel the cell. Archaeal flagella have a unique structure which lacks a central channel. Similar to bacterial type IV pilins , the archaeal proteins (archaellins) are made with class 3 signal peptides and they are processed by a type IV prepilin peptidase-like enzyme. The archaellins are typically modified by
4545-447: The cell body, helically twining about each other to form a thick structure (easily visible with the light microscope) called a " fascicle ". In some Vibrio spp. (particularly Vibrio parahaemolyticus ) and related bacteria such as Aeromonas , two flagellar systems co-exist, using different sets of genes and different ion gradients for energy. The polar flagella are constitutively expressed and provide motility in bulk fluid, while
4646-407: The cell's direction of motion is unfavorable (e.g., away from a chemical attractant), tumbles are no longer suppressed and occur much more often, with the chance that the cell will be thus reoriented in the correct direction. Even if all flagella would rotate clockwise, however, they often cannot form a bundle due to geometrical and hydrodynamic reasons. Aiming to emphasize the distinction between
4747-567: The coiled DNA areas of prokaryotic bacteria and the well-defined eukaryotic nucleus. This group, however, does contain typically eukaryotic organelles , such as Golgi bodies, mitochondria, and chloroplasts. Jakob Schiller (1931–1937) provided a description of all the species, both marine and freshwater, known at that time. Later, Alain Sournia (1973, 1978, 1982, 1990, 1993) listed the new taxonomic entries published after Schiller (1931–1937). Sournia (1986) gave descriptions and illustrations of
4848-416: The conclusion that encystment is associated with sexual reproduction. These observations also gave credence to the idea that microalgal encystment is essentially a process whereby zygotes prepare themselves for a dormant period. Because the resting cysts studied until that time came from sexual processes, dormancy was associated with sexuality, a presumption that was maintained for many years. This attribution
4949-480: The cysts remain in the sediment layer during conditions unfavorable for vegetative growth and, from there, reinoculate the water column when favorable conditions are restored. Indeed, during dinoflagellate evolution the need to adapt to fluctuating environments and/or to seasonality is thought to have driven the development of this life cycle stage. Most protists form dormant cysts in order to withstand starvation and UV damage. However, there are enormous differences in
5050-405: The development of cryo-electron microscopy . The best understood parts are the parts between the inner and outer membrane , that is, the scaffolding rings of the inner membrane (IM), the scaffolding pairs of the outer membrane (OM), and the rod/needle (injectisome) or rod/hook (flagellum) sections. The bacterial flagellum is driven by a rotary engine ( Mot complex ) made up of protein, located at
5151-488: The dinoflagellates Karenia brevis , Karenia mikimotoi , and Karlodinium micrum have acquired other pigments through endosymbiosis, including fucoxanthin . This suggests their chloroplasts were incorporated by several endosymbiotic events involving already colored or secondarily colorless forms. The discovery of plastids in the Apicomplexa has led some to suggest they were inherited from an ancestor common to
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#17328013953695252-419: The flagella lagging behind the body. During flagellar assembly, components of the flagellum pass through the hollow cores of the basal body and the nascent filament. During assembly, protein components are added at the flagellar tip rather than at the base. In vitro , flagellar filaments assemble spontaneously in a solution containing purified flagellin as the sole protein. At least 10 protein components of
5353-447: The flagellar apparatus are the transition zone (where the axoneme and basal body meet) and the root system (microtubular or fibrilar structures that extend from the basal bodies into the cytoplasm), more variable and useful as indicators of phylogenetic relationships of eukaryotes. Other structures, more uncommon, are the paraflagellar (or paraxial, paraxonemal) rod, the R fiber, and the S fiber. For surface structures, see below. Each of
5454-405: The flagellum still works, though sometimes at reduced efficiency. Moreover, with many proteins unique to some number across species, diversity of bacterial flagella composition was higher than expected. Hence, the flagellar apparatus is clearly very flexible in evolutionary terms and perfectly able to lose or gain protein components. For instance, a number of mutations have been found that increase
5555-427: The flagellum's anchor point on the inner cell membrane. The engine is powered by proton-motive force , i.e., by the flow of protons (hydrogen ions) across the bacterial cell membrane due to a concentration gradient set up by the cell's metabolism ( Vibrio species have two kinds of flagella, lateral and polar, and some are driven by a sodium ion pump rather than a proton pump ). The rotor transports protons across
5656-529: The fusion of haploid gametes from motile planktonic vegetative stages to produce diploid planozygotes that eventually form cysts, or hypnozygotes , whose germination is subject to both endogenous and exogenous controls. Endogenously, a species-specific physiological maturation minimum period (dormancy) is mandatory before germination can occur. Thus, hypnozygotes were also referred to as "resting" or "resistant" cysts, in reference to this physiological trait and their capacity following dormancy to remain viable in
5757-459: The genus Symbiodinium ). The association between Symbiodinium and reef-building corals is widely known. However, endosymbiontic Zooxanthellae inhabit a great number of other invertebrates and protists, for example many sea anemones , jellyfish , nudibranchs , the giant clam Tridacna , and several species of radiolarians and foraminiferans . Many extant dinoflagellates are parasites (here defined as organisms that eat their prey from
5858-401: The growth of its competitors, thus achieving dominance. Dinoflagellates sometimes bloom in concentrations of more than a million cells per millilitre. Under such circumstances, they can produce toxins (generally called dinotoxins ) in quantities capable of killing fish and accumulating in filter feeders such as shellfish , which in turn may be passed on to people who eat them. This phenomenon
5959-504: The hollow, rod-like "plug" in their centers extending out through the plasma membrane. The similarities between bacterial flagella and bacterial secretory system structures and proteins provide scientific evidence supporting the theory that bacterial flagella evolved from the type-three secretion system (TTSS). The atomic structure of both bacterial flagella as well as the TTSS injectisome have been elucidated in great detail, especially with
6060-583: The increase in the requirement of the torque or speed more MotAB are employed. Because the flagellar motor has no on-off switch, the protein epsE is used as a mechanical clutch to disengage the motor from the rotor, thus stopping the flagellum and allowing the bacterium to remain in one place. The production and rotation of a flagellum can take up to 10% of an Escherichia coli cell's energy budget and has been described as an "energy-guzzling machine". Its operation generates reactive oxygen species that elevates mutation rates. The cylindrical shape of flagella
6161-721: The inside, i.e. endoparasites , or that remain attached to their prey for longer periods of time, i.e. ectoparasites). They can parasitize animal or protist hosts. Protoodinium, Crepidoodinium, Piscinoodinium , and Blastodinium retain their plastids while feeding on their zooplanktonic or fish hosts. In most parasitic dinoflagellates, the infective stage resembles a typical motile dinoflagellate cell. Three nutritional strategies are seen in dinoflagellates: phototrophy , mixotrophy , and heterotrophy . Phototrophs can be photoautotrophs or auxotrophs . Mixotrophic dinoflagellates are photosynthetically active, but are also heterotrophic. Facultative mixotrophs, in which autotrophy or heterotrophy
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#17328013953696262-485: The largest groups of marine eukaryotes, although substantially smaller than diatoms . Some species are endosymbionts of marine animals and play an important part in the biology of coral reefs . Other dinoflagellates are unpigmented predators on other protozoa, and a few forms are parasitic (for example, Oodinium and Pfiesteria ). Some dinoflagellates produce resting stages, called dinoflagellate cysts or dinocysts , as part of their lifecycles; this occurs in 84 of
6363-444: The lateral flagella are expressed when the polar flagella meet too much resistance to turn. These provide swarming motility on surfaces or in viscous fluids. Bundling is an event that can happen in multi-flagellated cells, bundling the flagella together and causing them to rotate in a coordinated manner. Flagella are left-handed helices, and when rotated counter-clockwise by their rotors, they can bundle and rotate together. When
6464-432: The latter long-term (resting) cysts. However, during the last two decades further knowledge has highlighted the great intricacy of dinoflagellate life histories. More than 10% of the approximately 2000 known marine dinoflagellate species produce cysts as part of their life cycle (see diagram on the right). These benthic phases play an important role in the ecology of the species, as part of a planktonic-benthic link in which
6565-498: The main cell vacuole. They contain dinoflagellate luciferase , the main enzyme involved in dinoflagellate bioluminescence, and luciferin , a chlorophyll-derived tetrapyrrole ring that acts as the substrate to the light-producing reaction. The luminescence occurs as a brief (0.1 sec) blue flash (max 476 nm) when stimulated, usually by mechanical disturbance. Therefore, when mechanically stimulated—by boat, swimming, or waves, for example—a blue sparkling light can be seen emanating from
6666-405: The main phenotypic, physiological and resistance properties of each dinoflagellate species cysts. Unlike in higher plants most of this variability, for example in dormancy periods, has not been proven yet to be attributed to latitude adaptation or to depend on other life cycle traits. Thus, despite recent advances in the understanding of the life histories of many dinoflagellate species, including
6767-1195: The marine genera of dinoflagellates, excluding information at the species level. The latest index is written by Gómez. English-language taxonomic monographs covering large numbers of species are published for the Gulf of Mexico, the Indian Ocean, the British Isles, the Mediterranean and the North Sea. The main source for identification of freshwater dinoflagellates is the Süsswasser Flora . Calcofluor-white can be used to stain thecal plates in armoured dinoflagellates. Dinoflagellates are found in all aquatic environments: marine, brackish, and fresh water, including in snow or ice. They are also common in benthic environments and sea ice. All Zooxanthellae are dinoflagellates and most of them are members within Symbiodiniaceae (e.g.
6868-496: The membrane, and is turned in the process. The rotor alone can operate at 6,000 to 100,000 rpm , but with the flagellar filament attached usually only reaches 200 to 1000 rpm. The direction of rotation can be changed by the flagellar motor switch almost instantaneously, caused by a slight change in the position of a protein, FliG , in the rotor. The torque is transferred from the MotAB to the torque helix on FliG's D5 domain and with
6969-741: The motility of E. coli . Additional evidence for the evolution of bacterial flagella includes the existence of vestigial flagella, intermediate forms of flagella and patterns of similarities among flagellar protein sequences, including the observation that almost all of the core flagellar proteins have known homologies with non-flagellar proteins. Furthermore, several processes have been identified as playing important roles in flagellar evolution, including self-assembly of simple repeating subunits, gene duplication with subsequent divergence, recruitment of elements from other systems ('molecular bricolage') and recombination. Different species of bacteria have different numbers and arrangements of flagella, named using
7070-405: The motor is highly adaptive to different signals. In the model describing chemotaxis ("movement on purpose") the clockwise rotation of a flagellum is suppressed by chemical compounds favorable to the cell (e.g. food). When moving in a favorable direction, the concentration of such chemical attractants increases and therefore tumbles are continually suppressed, allowing forward motion; likewise, when
7171-411: The number of flagella, cells may be: (remembering that some authors use "ciliated" instead of "flagellated") According to the place of insertion of the flagella: According to the beating pattern: Other terms related to the flagellar type: The archaellum possessed by some species of Archaea is superficially similar to the bacterial flagellum; in the 1980s, they were thought to be homologous on
7272-522: The only other dinoflagellate genera known to use this particular feeding mechanism. Katodinium (Gymnodinium) fungiforme , commonly found as a contaminant in algal or ciliate cultures, feeds by attaching to its prey and ingesting prey cytoplasm through an extensible peduncle. Two related species, polykrikos kofoidii and neatodinium, shoots out a harpoon-like organelle to capture prey. Some mixotrophic dinoflagellates are able to produce neurotoxins that have anti-grazing effects on larger copepods and enhance
7373-408: The order Gymnodiniales , suborder Actiniscineae . The formation of thecal plates has been studied in detail through ultrastructural studies. 'Core dinoflagellates' ( dinokaryotes ) have a peculiar form of nucleus , called a dinokaryon , in which the chromosomes are attached to the nuclear membrane . These carry reduced number of histones . In place of histones, dinoflagellate nuclei contain
7474-464: The original peridinin plastids or new plastids acquired from other lineages of unicellular algae through endosymbiosis. The remaining species have lost their photosynthetic abilities and have adapted to a heterotrophic, parasitic or kleptoplastic lifestyle. Most (but not all) dinoflagellates have a dinokaryon , described below (see: Life cycle , below). Dinoflagellates with a dinokaryon are classified under Dinokaryota , while dinoflagellates without
7575-420: The outer 9 doublet microtubules extends a pair of dynein arms (an "inner" and an "outer" arm) to the adjacent microtubule; these produce force through ATP hydrolysis. The flagellar axoneme also contains radial spokes , polypeptide complexes extending from each of the outer nine microtubule doublets towards the central pair, with the "head" of the spoke facing inwards. The radial spoke is thought to be involved in
7676-489: The phylum Dinoflagellata and are usually considered protists . Dinoflagellates are mostly marine plankton , but they are also common in freshwater habitats . Their populations vary with sea surface temperature , salinity , and depth. Many dinoflagellates are photosynthetic , but a large fraction of these are in fact mixotrophic , combining photosynthesis with ingestion of prey ( phagotrophy and myzocytosis ). In terms of number of species, dinoflagellates are one of
7777-660: The predator more vulnerable to predation from higher trophic levels. Bioluminescent dinoflagellate ecosystem bays are among the rarest and most fragile, with the most famous ones being the Bioluminescent Bay in La Parguera, Lajas , Puerto Rico; Mosquito Bay in Vieques, Puerto Rico ; and Las Cabezas de San Juan Reserva Natural Fajardo, Puerto Rico . Also, a bioluminescent lagoon is near Montego Bay, Jamaica, and bioluminescent harbors surround Castine, Maine. Within
7878-537: The process by which axonemal subunits, transmembrane receptors , and other proteins are moved up and down the length of the flagellum, is essential for proper functioning of the flagellum, in both motility and signal transduction. Eukaryotic flagella or cilia, probably an ancestral characteristic, are widespread in almost all groups of eukaryotes, as a relatively perennial condition, or as a flagellated life cycle stage (e.g., zoids , gametes , zoospores , which may be produced continually or not). The first situation
7979-453: The regulation of flagellar motion, although its exact function and method of action are not yet understood. The regular beat patterns of eukaryotic cilia and flagella generate motion on a cellular level. Examples range from the propulsion of single cells such as the swimming of spermatozoa to the transport of fluid along a stationary layer of cells such as in the respiratory tract . Although eukaryotic cilia and flagella are ultimately
8080-414: The role of cyst stages, many gaps remain in knowledge about their origin and functionality. Recognition of the capacity of dinoflagellates to encyst dates back to the early 20th century, in biostratigraphic studies of fossil dinoflagellate cysts. Paul Reinsch was the first to identify cysts as the fossilized remains of dinoflagellates. Later, cyst formation from gamete fusion was reported, which led to
8181-413: The rotors reverse direction, thus rotating clockwise, the flagellum unwinds from the bundle. This may cause the cell to stop its forward motion and instead start twitching in place, referred to as tumbling . Tumbling results in a stochastic reorientation of the cell, causing it to change the direction of its forward swimming. It is not known which stimuli drive the switch between bundling and tumbling, but
8282-463: The same function of providing motility. The Latin word flagellum means " whip " to describe its lash-like swimming motion. The flagellum in archaea is called the archaellum to note its difference from the bacterial flagellum. Eukaryotic flagella and cilia are identical in structure but have different lengths and functions. Prokaryotic fimbriae and pili are smaller, and thinner appendages, with different functions. Cilia are attached to
8383-432: The same, they are sometimes classed by their pattern of movement, a tradition from before their structures have been known. In the case of flagella, the motion is often planar and wave-like, whereas the motile cilia often perform a more complicated three-dimensional motion with a power and recovery stroke. Yet another traditional form of distinction is by the number of 9+2 organelles on the cell. Intraflagellar transport ,
8484-406: The sea surface. Dinoflagellate bioluminescence is controlled by a circadian clock and only occurs at night. Luminescent and nonluminescent strains can occur in the same species. The number of scintillons is higher during night than during day, and breaks down during the end of the night, at the time of maximal bioluminescence. The luciferin-luciferase reaction responsible for the bioluminescence
8585-431: The sediments for long periods of time. Exogenously, germination is only possible within a window of favorable environmental conditions. Yet, with the discovery that planozygotes were also able to divide it became apparent that the complexity of dinoflagellate life cycles was greater than originally thought. Following corroboration of this behavior in several species, the capacity of dinoflagellate sexual phases to restore
8686-475: The smallest known eye. Some athecate species have an internal skeleton consisting of two star-like siliceous elements that has an unknown function, and can be found as microfossils . Tappan gave a survey of dinoflagellates with internal skeletons . This included the first detailed description of the pentasters in Actiniscus pentasterias , based on scanning electron microscopy . They are placed within
8787-401: The so-called cingulum (or cigulum) runs around the cell, thus dividing it into an anterior (episoma) and posterior (hyposoma). If and only if a theca is present, the parts are called epitheca and hypotheca, respectively. Posteriorly, starting from the transverse groove, there is a longitudinal furrow called the sulcus. The transverse flagellum strikes in the cingulum, the longitudinal flagellum in
8888-468: The stomach to reach the mucous lining where it may colonise the epithelium and potentially cause gastritis, and ulcers – a risk factor for stomach cancer . In some swarming bacteria , the flagellum can also function as a sensory organelle , being sensitive to wetness outside the cell. Across the three domains of Bacteria , Archaea , and Eukaryota , the flagellum has a different structure, protein composition, and mechanism of propulsion but shares
8989-475: The structure of archaella made significant progress beginning in the early 2010s, with the first atomic resolution structure of an archaella protein, the discovery of additional functions of archaella, and the first reports of archaella in Nanoarchaeota and Thaumarchaeota. The only fungi to have a single flagellum on their spores are the chytrids . In Batrachochytrium dendrobatidis the flagellum
9090-406: The sulcal region of the cell (either via water currents set up by the flagella or via pseudopodial extensions) and ingest the prey through the sulcus. In several Protoperidinium spp., e.g. P. conicum , a large feeding veil—a pseudopod called the pallium—is extruded to capture prey which is subsequently digested extracellularly (= pallium-feeding). Oblea , Zygabikodinium , and Diplopsalis are
9191-452: The sulcus. Together with various other structural and genetic details, this organization indicates a close relationship between the dinoflagellates, the Apicomplexa , and ciliates , collectively referred to as the alveolates . Dinoflagellate tabulations can be grouped into six "tabulation types": gymnodinoid , suessoid , gonyaulacoid – peridinioid , nannoceratopsioid , dinophysioid , and prorocentroid . Most Dinoflagellates have
9292-448: The surface of flagella and are used to swim or move fluid from one region to another. The three types of flagella are bacterial, archaeal, and eukaryotic. The flagella in eukaryotes have dynein and microtubules that move with a bending mechanism. Bacteria and archaea do not have dynein or microtubules in their flagella, and they move using a rotary mechanism. Other differences among these three types are: The bacterial flagellum
9393-428: The term tricho , from the Greek trichos meaning hair . Counterclockwise rotation of a monotrichous polar flagellum pushes the cell forward with the flagellum trailing behind, much like a corkscrew moving inside cork. Water on the microscopic scale is highly viscous , unlike usual water . Spirochetes , in contrast, have flagella called endoflagella arising from opposite poles of the cell, and are located within
9494-415: The two flagella are differentiated as in dinokonts, but they are not associated with grooves. Dinoflagellates have a complex cell covering called an amphiesma or cortex, composed of a series of membranes, flattened vesicles called alveoli (= amphiesmal vesicles) and related structures. In thecate ("armoured") dinoflagellates, these support overlapping cellulose plates to create a sort of armor called
9595-456: The two groups, but none of the more basal lines has them. All the same, the dinoflagellate cell consists of the more common organelles such as rough and smooth endoplasmic reticulum , Golgi apparatus , mitochondria , lipid and starch grains, and food vacuoles . Some have even been found with a light-sensitive organelle, the eyespot or stigma , or a larger nucleus containing a prominent nucleolus . The dinoflagellate Erythropsidinium has
9696-428: The two structures evolved separately from a common ancestor accounts for the protein similarities between the two structures, as well as their functional diversity. Some authors have argued that flagella cannot have evolved, assuming that they can only function properly when all proteins are in place. In other words, the flagellar apparatus is " irreducibly complex ". However, many proteins can be deleted or mutated and
9797-584: The vegetative phase, bypassing cyst formation, became well accepted. Further, in 2006 Kremp and Parrow showed the dormant resting cysts of the Baltic cold water dinoflagellates Scrippsiella hangoei and Gymnodinium sp. were formed by the direct encystment of haploid vegetative cells, i.e., asexually. In addition, for the zygotic cysts of Pfiesteria piscicida dormancy was not essential. Flagella A flagellum ( / f l ə ˈ dʒ ɛ l əm / ; pl. : flagella ) ( Latin for 'whip' or 'scourge')
9898-506: The ventral cell side (dinokont flagellation). They have a ribbon-like transverse flagellum with multiple waves that beats to the cell's left, and a more conventional one, the longitudinal flagellum, that beats posteriorly. The transverse flagellum is a wavy ribbon in which only the outer edge undulates from base to tip, due to the action of the axoneme which runs along it. The axonemal edge has simple hairs that can be of varying lengths. The flagellar movement produces forward propulsion and also
9999-468: The water column or sediment. Most symbiotic members of Symbiodiniaceae were previously assigned to the genus Symbiodinium ; however, recent genetic analysis has led to a taxonomic reorganization with several former members of Symbiodinium (previously "clades") reassigned to new genera within the Symbiodiniaceae family. Species formerly classified within Symbiodinum Clade A are retained in
10100-426: Was coincident with evolutionary theories about the origin of eukaryotic cell fusion and sexuality, which postulated advantages for species with diploid resting stages, in their ability to withstand nutrient stress and mutational UV radiation through recombinational repair, and for those with haploid vegetative stages, as asexual division doubles the number of cells. Nonetheless, certain environmental conditions may limit
10201-536: Was once considered to be an intermediate between the nucleoid region of prokaryotes and the true nuclei of eukaryotes , so were termed " mesokaryotic ", but now are considered derived rather than primitive traits (i. e. ancestors of dinoflagellates had typical eukaryotic nuclei). In addition to dinokaryotes, DVNPs can be found in a group of basal dinoflagellates (known as Marine Alveolates , "MALVs") that branch as sister to dinokaryotes ( Syndiniales ). Dinoflagellates are protists and have been classified using both
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