Raphidophytes are a small group of eukaryotic

Eukaryote

A eukaryote is an organism whose cells contain complex structures enclosed within membranes. Eukaryotes may more formally be referred to as the taxon Eukarya or Eukaryota. The defining membrane-bound structure that sets eukaryotic cells apart from prokaryotic cells is the nucleus, or nuclear...

 algae that includes both marine

Marine (ocean)

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...

 and freshwater

Fresh Water

Fresh Water is the debut album by Australian rock and blues singer Alison McCallum, released in 1972. Rare for an Australian artist at the time, it came in a gatefold sleeve...

 species

Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

. All raphidophytes are unicellular, with large cells (50 → 100 μm

Micrometre

A micrometer , is by definition 1×10-6 of a meter .In plain English, it means one-millionth of a meter . Its unit symbol in the International System of Units is μm...

) but no cell walls. Raphidophytes possess a pair of flagella

Flagellum

A flagellum is a tail-like projection that protrudes from the cell body of certain prokaryotic and eukaryotic cells, and plays the dual role of locomotion and sense organ, being sensitive to chemicals and temperatures outside the cell. There are some notable differences between prokaryotic and...

, organised such that both originate from the same invagination

Invagination

Invagination means to fold inward or to sheath. In biology, this can refer to a number of processes.* Invagination is the morphogenetic processes by which an embryo takes form, and is the initial step of gastrulation, the massive reorganization of the embryo from a simple spherical ball of cells,...

 (or gullet). One flagellum points forwards, while the other, covered in hair-like mastigonemes

Mastigonemes

Mastigonemes are lateral "hairs" found covering the flagella of heterokont and cryptophyte algae. They are approximately 15 nm in diameter, and usually consist of a tubular shaft that itself terminates in smaller "hairs". It is believed that they assist in locomotion by increasing the surface...

, points backwards across the cell surface, lying within a ventral

Anatomical terms of location

Standard anatomical terms of location are designations employed in science that deal with the anatomy of animals to avoid ambiguities that might otherwise arise. They are not language-specific, and thus require no translation...

 groove. Raphidophytes contain numerous ellipsoid

Ellipse

In geometry, an ellipse is a plane curve that results from the intersection of a cone by a plane in a way that produces a closed curve. Circles are special cases of ellipses, obtained when the cutting plane is orthogonal to the cone's axis...

 chloroplast

Chloroplast

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.Chloroplasts are green...

s, which contain chlorophyll

Chlorophyll

Chlorophyll is a green pigment found in almost all plants, algae, and cyanobacteria. Its name is derived from the Greek words χλωρος, chloros and φύλλον, phyllon . Chlorophyll is an extremely important biomolecule, critical in photosynthesis, which allows plants to obtain energy from light...

s a, c₁ and c₂. They also make use of accessory pigment

Accessory pigment

Accessory pigments are light-absorbing compounds, found in photosynthetic organisms, that work in conjunction with chlorophyll a. They include other forms of this pigment, such as chlorophyll b in green algal and higher plant antennae, while other algae may contain chlorophyll c or d...

s including β-carotene

Carotene

The term carotene is used for several related unsaturated hydrocarbon substances having the formula C40Hx, which are synthesized by plants but cannot be made by animals. Carotene is an orange photosynthetic pigment important for photosynthesis. Carotenes are all coloured to the human eye...

 and diadinoxanthin. Unlike other heterokontophytes, raphidophytes do not possess the photoreceptive organelle

Eyespot apparatus

The eyespot apparatus is a photoreceptive organelle found in the flagellate cells of green algae and other unicellular photosynthetic organisms such as euglenids. It allows the cells to sense light direction and intensity and respond to it by swimming either towards the light or away from the...

 (or eyespot) typical of this group.

In terms of ecology

Ecology

Ecology is the scientific study of the relations that living organisms have with respect to each other and their natural environment. Variables of interest to ecologists include the composition, distribution, amount , number, and changing states of organisms within and among ecosystems...

, raphidophytes occur as photosynthetic

Photosynthesis

Photosynthesis is a chemical 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...

 autotroph

Autotroph

An autotroph, or producer, is an organism that produces complex organic compounds from simple inorganic molecules using energy from light or inorganic chemical reactions . They are the producers in a food chain, such as plants on land or algae in water...

s across a range of aquatic

Aquatic ecosystem

An aquatic ecosystem is an ecosystem in a body of water. Communities of organisms that are dependent on each other and on their environment live in aquatic ecosystems. The two main types of aquatic ecosystems are marine ecosystems and freshwater ecosystems....

 systems. Freshwater species are more common in acid

Acid

An acid is a substance which reacts with a base. Commonly, acids can be identified as tasting sour, reacting with metals such as calcium, and bases like sodium carbonate. Aqueous acids have a pH of less than 7, where an acid of lower pH is typically stronger, and turn blue litmus paper red...

ic waters, such as pools in bog

Bog

A bog, quagmire or mire is a wetland that accumulates acidic peat, a deposit of dead plant material—often mosses or, in Arctic climates, lichens....

s. Marine species often produce large blooms

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...

 in summer, particularly in coastal waters

Coast

A coastline or seashore is the area where land meets the sea or ocean. A precise line that can be called a coastline cannot be determined due to the dynamic nature of tides. The term "coastal zone" can be used instead, which is a spatial zone where interaction of the sea and land processes occurs...

. Off the Japan

Japan

Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

ese coast, the resulting red tide

Red tide

Red tide is a common name for a phenomenon also known as an algal bloom , an event in which estuarine, marine, or fresh water algae accumulate rapidly in the water column and results in discoloration of the surface water. It is usually found in coastal areas...

s often cause disruption to fish farms

Fish farming

Fish farming is the principal form of aquaculture, while other methods may fall under mariculture. Fish farming involves raising fish commercially in tanks or enclosures, usually for food. A facility that releases young fish into the wild for recreational fishing or to supplement a species'...

, although raphidophytes are not usually responsible for toxic

Toxicity

Toxicity is the degree to which a substance can damage a living or non-living organisms. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a substructure of the organism, such as a cell or an organ , such as the liver...

 blooms.

See also

• Chattonella
• Fibrocapsa
• Gonyostomum
• Haramonas
• Heterosigma
• Vacuolaria