The dinoflagellates (Gk Greek , an independent branch of the Indo-European family of languages, is the language of the Greeks. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. In its ancient form, it is the language of classical ancient Greek literature and the New Testament of. δῖνος dinos [whirling] and Lt Latin is an Italic language originally spoken in Latium and Ancient Rome. With the Roman conquest, Latin was spread to countries around the Mediterranean, including a large part of Europe. Romance languages such as Aragonese, Corsican, Catalan, French, Italian, Portuguese, Romanian, Sardinian, Spanish and others, are descended from Latin, while. flagellum [whip or scourge]) are a large group of flagellate Flagellates are organisms with one or more whip-like organelles called flagella. Some cells in animals may be flagellate, for instance the spermatozoa of most phyla. Higher plants and fungi do not produce flagellate cells, but the closely related green algae and chytrids do. Many protists take the form of single-celled flagellates protists Protists are a diverse group of eukaryotic microorganisms. which include mostly unicellular organisms that do not fit into the other kingdoms. Historically, protists were treated as the kingdom Protista, which includes mostly unicellular organisms that do not fit into the other kingdoms, but this group is contested in modern taxonomy. Instead, it. Most are marine Marine is an umbrella term. As an adjective it is usually applicable to things relating to the sea or ocean, such as marine biology, marine ecology and marine geology. As a noun it can be a term for a certain kind of navy, or those enlisted in such a navy plankton Plankton are any drifting organisms that inhabit the pelagic zone of oceans, seas, or bodies of fresh water. Plankton are defined by their ecological niche rather than phylogenetic or taxonomic classification. They provide a crucial source of food to larger, more familiar aquatic organisms such as fish and cetacea, but they are common in fresh water Freshwater or fresh water is naturally occurring water on the Earth's surface in bogs, ponds, lakes, rivers and streams, and underground as groundwater in aquifers and underground streams. Freshwater is characterized by having low concentrations of dissolved salts and other total dissolved solids. The term specifically excludes seawater and habitats as well. Their populations are distributed depending on temperature In practical terms, the exact meaning of surface varies according to the measurement method used. A satellite infrared radiometer indirectly measures the temperature of a very thin layer of about 10 micrometres thick of the ocean which leads to the phrase skin temperature (because infrared radiation is emitted from this layer). A microwave, salinity Salinity is the saltiness or dissolved salt content of a body of water. It is a general term used to describe the levels of different salts such as sodium chloride, magnesium and calcium sulfates, and bicarbonates. Salinity in Australian English and North American English may also refer to the salt content of soil, or depth. About half of all dinoflagellates are photosynthetic Photosynthesis is a process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can create their own food. In plants, algae, and cyanobacteria,, and these make up the largest group of eukaryotic A eukaryote is an organism whose cells contain complex structures enclosed within membranes. The defining membrane-bound structure that sets eukaryotic cells apart from prokaryotic cells is the nucleus, or nuclear envelope, within which the genetic material is carried. The presence of a nucleus gives eukaryotes their name, which comes from the algae Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms. The largest and most complex marine forms are called seaweeds. They are photosynthetic, like plants, and "simple" because they lack the many distinct organs found in land plants aside from the diatoms Diatoms are a major group of algae, and are one of the most common types of phytoplankton. Most diatoms are unicellular, although they can exist as colonies in the shape of filaments or ribbons , fans (e.g. Meridion), zigzags (e.g. Tabellaria), or stellate colonies (e.g. Asterionella). Diatoms are producers within the food chain. A characteristic. Being primary producers makes them an important part of the aquatic food chain. Some species, called zooxanthellae Zooxanthellae are flagellate protozoa that are golden-brown intracellular endosymbionts of various marine animals and protozoa, especially anthozoans such as the scleractinian corals and the tropical sea anemone, Aiptasia, are endosymbionts An endosymbiont is any organism that lives within the body or cells of another organism, i.e. forming an endosymbiosis . Examples are nitrogen-fixing bacteria (called rhizobia) which live in root nodules on legume roots, single-celled algae inside reef-building corals, and bacterial endosymbionts that provide essential nutrients to about 10%–15% of marine animals and protozoa, and play an important part in the biology of coral Corals are marine organisms in class Anthozoa of phylum Cnidaria typically living in compact colonies of many identical individual "polyps". The group includes the important reef builders that inhabit tropical oceans, which secrete calcium carbonate to form a hard skeleton reefs. Other dinoflagellates are colorless predators on other protozoa, and a few forms are parasitic Parasitism is a type of symbiotic relationship between organisms of different species where one organism, the parasite, benefits at the expense of the host (see for example Oodinium Oödinium is a genus of microscopic parasitic dinoflagellates. They live off salt and fresh water fish, causing a type of fish velvet disease (also called gold dust disease). One species has also been recorded on various cnidarians, Pfiesteria Pfiesteria is a genus of heterotrophic dinoflagellates that has been associated with harmful algal blooms and fish kills. Pfiesteria complex organisms were claimed to be responsible for large fish kills in the 1980s and 1990s on the coast of North Carolina and in tributaries of the Chesapeake Bay. In reaction to the toxic outbreaks, six states).

It is sometimes equated with the order Dinoflagellata.^[1] It is also sometimes equated with the class Dinophyceae.^[2]

An algal bloom An algal bloom is a rapid increase or accumulation in the population of algae in an aquatic system. Algal blooms may occur in freshwater as well as marine environments. Typically, only one or a small number of phytoplankton species are involved, and some blooms may be recognized by discoloration of the water resulting from the high density of of dinoflagellates can result in a visible coloration of the water colloquially known as red tide An algal bloom is a rapid increase or accumulation in the population of algae in an aquatic system. Algal blooms may occur in freshwater as well as marine environments. Typically, only one or a small number of phytoplankton species are involved, and some blooms may be recognized by discoloration of the water resulting from the high density of.

Classification

In 1753 the first modern dinoflagellates were described by Baker and named by Muller in 1773.^[3] The term derives from the Greek word δῖνος (dinos), meaning 'whirling,' and Latin flagellum, a diminutive term for a whip or scourge.

These same dinoflagellates were first defined by Otto Bütschli in 1885 as the flagellate order dinoflagellida. Botanists treated them as a division of algae, named Pyrrhophyta ("fire algae"; Greek pyrrhos, fire) after the bioluminscent forms, or Dinophyta. At various times the cryptomonads The cryptomonads are a group of algae, most of which have chloroplasts. They are common in freshwater, and also occur in marine and brackish habitats. Each cell is around 10-50 μm in size and flattened in shape, with an anterior groove or pocket. At the edge of the pocket there are typically two slightly unequal flagella, ebriids The Ebridea is a group of phagotrophic flagellate protist present in marine coastal plankton communities worldwide. Ebria tripartita is one of two described extant species in the Ebridea, and ellobiopsids have been included here, but only the last are now considered close relatives. Dinoflagellates have a known ability to evolve from non-cyst to cyst forming strategies which makes it extremely difficult to recreate their evolutionary history.

Part of the challenge in dinoflagellate taxonomy and nomenclature is that they have been independently classified by the rules of zoology Zoology , occasionally also spelt zo-ölogy, is the branch of biology that focuses on the structure, function, behavior, and evolution of animals and botany Botany, plant science, phytology, or plant biology is a branch of biology that involves the scientific study of plant life. Botany covers a wide range of scientific disciplines concerned with the study of plants, algae and fungi, including structure, growth, reproduction, metabolism, development, diseases, chemical properties, and evolutionary, and only recently have the disciplines converged.^[4]

Most (but not all) dinoflagellates have a dinokaryon (see: Life-cycle, below.).^[5] Dinoflagellates with a dinokaryon are classified under Dinokaryota, while dinoflagellates without a dinokaryon are classified under Syndiniales.

Although classified as eukaryotes A eukaryote is an organism whose cells contain complex structures enclosed within membranes. The defining membrane-bound structure that sets eukaryotic cells apart from prokaryotic cells is the nucleus, or nuclear envelope, within which the genetic material is carried. The presence of a nucleus gives eukaryotes their name, which comes from the, the dinoflagellate nuclei are not characteristically eukaryotic, as they lack histones In biology, histones are strongly alkaline proteins found in eukaryotic cell nuclei, which package and order the DNA into structural units called nucleosomes. They are the chief protein components of chromatin, act as spools around which DNA winds, and play a role in gene regulation. Without histones, the unwound DNA in chromosomes would be very, nucleosomes and maintain continually condensed chromosomes during mitosis Mitosis is the process by which a eukaryotic cell separates the chromosomes in its cell nucleus into two identical sets in two nuclei. It is generally followed immediately by cytokinesis, which divides the nuclei, cytoplasm, organelles and cell membrane into two cells containing roughly equal shares of these cellular components. Mitosis and. In fact, Dodge (1966)^[6] termed the dinoflagellate nucleus as ‘mesokaryotic’, due to its possession of intermediate characteristics between the coiled DNA areas of prokaryotic bacteria and the well-defined eukaryotic nucleus. This group, however, does contain typically eukaryotic organelles In cell biology, an organelle is a specialized subunit within a cell that has a specific function, and is usually separately enclosed within its own lipid bilayer, such as golgi bodies, mitochondria and chloroplasts ^[7]

Morphology

Most dinoflagellates are unicellular forms with two flagella A flagellum is a tail-like projection that protrudes from the cell body of certain prokaryotic and eukaryotic cells, and functions in locomotion. There are some notable differences between prokaryotic and eukaryotic flagella, such as protein composition, structure, and mechanism of propulsion. An example of a flagellated bacterium is the ulcer-. One of these extends towards the posterior, called the longitudinal flagellum, while the other forms a lateral circle, called the transverse flagellum. In many forms these are set into grooves, called the sulcus and cingulum. The transverse flagellum provides most of the force propelling the cell, and often imparts to it a distinctive whirling motion, which is what gives them their name. The longitudinal flagellum acts mainly as a rudder, but provides a small amount of propulsive force as well.

Dinoflagellates have a complex cell covering called an amphiesma, composed of flattened vesicles A vesicle like a liposome can be visualised as a bubble of liquid within another liquid, a supamolecular assembly made up of many different molecules. More technically, a vesicle is a small membrane-enclosed sac that can store or transport substances. Vesicles can form naturally because of the properties of lipid membranes , or they may be, called alveoli. In some forms, these support overlapping cellulose Cellulose is an organic compound with the formula n, a polysaccharide consisting of a linear chain of several hundred to over ten thousand β(1→4) linked D-glucose units plates that make up a sort of armor called the theca. These come in various shapes and arrangements, depending on the species and sometimes stage of the dinoflagellate. Fibrous extrusomes Extrusomes are membrane-bound structures in some eukaryotes which, under certain conditions, discharge their contents outside the cell. There are a variety of different types, probably not homologous, and serving various functions are also found in many forms. Together with various other structural and genetic details, this organization indicates a close relationship between the dinoflagellates, Apicomplexa The Apicomplexa are a large group of protists, most of which possess a unique organelle called apicoplast and an apical complex structure involved in penetrating a host's cell. They are unicellular, spore-forming, and exclusively parasites of animals. Motile structures such as flagella or pseudopods are absent except in certain gamete stages. This, and ciliates The ciliates are a group of protozoans characterized by the presence of hair-like organelles called cilia, which are identical in structure to flagella but typically shorter and present in much larger numbers with a different undulating pattern than flagella. Cilia occur in all members of the group and are variously used in swimming, crawling,, collectively referred to as the alveolates The most notable shared characteristic is the presence of cortical alveoli, flattened vesicles packed into a continuous layer supporting the membrane, typically forming a flexible pellicle. In dinoflagellates they often form armor plates. Alveolates have mitochondria with tubular cristae, and their flagella or cilia have a distinct structure.

The chloroplasts Chloroplasts are organelles found in plant cells and other eukaryotic organisms that conduct photosynthesis. Chloroplasts capture light energy to conserve free energy in the form of ATP and reduce NADP to NADPH through a complex set of processes called photosynthesis in most photosynthetic dinoflagellates are bound by three membranes The 'e is one biological membrane separating the interior of a cell from the outside environment, suggesting they were probably derived from some ingested algae, and contain chlorophylls Chlorophyll is a green pigment found in all plants, algae, and cyanobacteria. Its name is derived from the Greek χλωρός (chloros "green") and φύλλον (phyllon "leaf"). Chlorophyll absorbs light most strongly in the blue portion of the electromagnetic spectrum, followed by the red portion. However, it is a poor a and c and either peridinin Peridinin is a light-harvesting carotenoid, a pigment associated with chlorophyll and found in the peridinin-chlorophyll-protein light-harvesting complex in dinoflagellates, best studied in Amphidinium carterae. The PCP complex is unique in its high ratio of peridinin to chlorophyll; most light-harvesting complexes contain more chlorophyll than or fucoxanthin Fucoxanthin is a xanthophyll, with formula C42H58O6. It is found as an accessory pigment in the chloroplasts of brown algae and most other heterokonts, giving them a brown or olive-green color. Fucoxanthin absorbs light primarily in the blue-green to yellow-green part of the visible spectrum, peaking at around 510-525 nm by various estimates and, as well as various other accessory pigments A pigment is a material that changes the color of reflected or transmitted light as the result of wavelength-selective absorption. This physical process differs from fluorescence, phosphorescence, and other forms of luminescence, in which a material emits light. However, a few such as zooxanthellae, which are endosymbionts of marine animals such as coral, have chloroplasts with different pigmentation, sexuality, and structure, some of which retain a nucleus In cell biology, the nucleus , also sometimes referred to as the "control center", is a membrane-enclosed organelle found in eukaryotic cells. It contains most of the cell's genetic material, organized as multiple long linear DNA molecules in complex with a large variety of proteins, such as histones, to form chromosomes. The genes. This suggests that chloroplasts were incorporated by several endosymbiotic events involving already colored or secondarily colorless forms. The discovery of plastids in Apicomplexa have led some to suggest they were inherited from an ancestor common to the two groups, but none of the more basal lines have them. All the same, the dinoflagellate still 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 light sensitive organelle such as the eyespot or a larger nucleus containing a prominent nucleolus. The dinoflagellate Erythropsidium has the smallest known eye Eyes are organs that detect light, and convert it to electro-chemical impulses in neurons. The simplest photoreceptors in conscious vision connect light to movement. In higher organisms complex neural pathways exist that connect the eye, via the optic nerve to the visual cortex and other areas of the brain. Complex optical systems with resolving.^[8]

Life cycle

Most dinoflagellates have a peculiar form of nucleus In cell biology, the nucleus , also sometimes referred to as the "control center", is a membrane-enclosed organelle found in eukaryotic cells. It contains most of the cell's genetic material, organized as multiple long linear DNA molecules in complex with a large variety of proteins, such as histones, to form chromosomes. The genes, called a dinokaryon, in which the chromosomes A chromosome is an organized structure of DNA and protein that is found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements and other nucleotide sequences. Chromosomes also contain DNA-bound proteins, which serve to package the DNA and control its functions. The word chromosome comes from the Greek χρῶμα are attached to the nuclear membrane. These lack histones In biology, histones are strongly alkaline proteins found in eukaryotic cell nuclei, which package and order the DNA into structural units called nucleosomes. They are the chief protein components of chromatin, act as spools around which DNA winds, and play a role in gene regulation. Without histones, the unwound DNA in chromosomes would be very and remain condensed throughout interphase rather than just during mitosis Mitosis is the process by which a eukaryotic cell separates the chromosomes in its cell nucleus into two identical sets in two nuclei. It is generally followed immediately by cytokinesis, which divides the nuclei, cytoplasm, organelles and cell membrane into two cells containing roughly equal shares of these cellular components. Mitosis and, which is closed and involves a unique external spindle. This sort of nucleus was once considered to be an intermediate between the nucleoid region of prokaryotes The prokaryotes are a group of organisms that lack a cell nucleus (= karyon), or any other membrane-bound organelles. They differ from the eukaryotes, which have a cell nucleus. Most are unicellular, but a few prokaryotes such as myxobacteria have multicellular stages in their life cycles. The word prokaryote comes from the Greek πρό- (pro-) & and the true nuclei of eukaryotes A eukaryote is an organism whose cells contain complex structures enclosed within membranes. The defining membrane-bound structure that sets eukaryotic cells apart from prokaryotic cells is the nucleus, or nuclear envelope, within which the genetic material is carried. The presence of a nucleus gives eukaryotes their name, which comes from the, and so were termed mesokaryotic, but now are considered advanced rather than primitive traits.

In most dinoflagellates, the nucleus is dikaryotic throughout the entire life cycle. They are usually haploid, and reproduce primarily through fission, but sexual reproduction also occurs.^[9] This takes place by fusion of two individuals to form a zygote, which may remain mobile in typical dinoflagellate fashion or may form a resting dinocyst, which later undergoes meiosis to produce new haploid cells.^{[clarification needed]}

When conditions become unfavourable, usually when nutrients become depleted or there is insufficient light, some dinoflagellate species alter their life cycle dramatically. Two vegetative cells will fuse together forming a planozygote. Next is a stage not much different from hibernation called hypnozygote, when the organism takes in excess fat and oil. At the same time its body enlarges and the shell gets harder. Sometimes even spikes are formed. When the weather allows it, these dinoflagellates break out of their shell and are in a temporary stage, planomeiocyte, when they quickly reform their individual thecae and return to the dinoflagellates at the beginning of the process.

Dinoflagellates sometimes bloom in concentrations of more than a million cells per millilitre. Some species produce neurotoxins, which in such quantities kill fish and accumulate in filter feeders such as shellfish, which in turn may pass them on to people who eat them. This phenomenon 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.

The same red tide mentioned above is more specifically produced when dinoflagellates are able to reproduce rapidly and copiously on account of the abundant nutrients in the water. Although the resulting red waves are an unusual sight, they contain toxins that not only affect all marine life in the ocean but the people who consume them as well.^[10] A specific carrier is shellfish. This can introduce both non-fatal and fatal illnesses. One such poison is saxitoxin, a powerful paralytic. Human inputs of phosphate further encourage these red tides, and consequently there is a strong interest in learning more about dinoflagellates, from both medical and economic perspectives.

Evolutionary history

Dinoflagellate cysts are found as microfossils from the Triassic period, and form a major part of the organic-walled marine microflora from the middle Jurassic, through the Cretaceous and Cenozoic to the present day. Because some species are adapted to different surface water conditions, these fossils from sediments can be used to reconstruct past surface ocean conditions.^[11] Arpylorus, from the Silurian of North Africa was at one time considered to be a dinoflagellate cyst, but this palynomorph is now considered to be part of the microfauna (Arthropoda). It is possible that some of the Paleozoic acritarchs also represent dinoflagellates.

Examples

• Noctiluca (Sea Ghost or "Fire of sea" : Origin of Bioluminescence.
• Ceratium
• Gonyaulax
• Gymnodinium

See also

• Algal bloom
• Ciguatera
• Paralytic shellfish poisoning (PSP)

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