Eustigmatophytes are a small group (17

genera Genus (; : genera ) is a taxonomic rank above species and below family as used in the biological classification of living and fossil organisms as well as viruses. In binomial nomenclature, the genus name forms the first part of the binomial s ...

; ~107

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

) of

eukaryotic The eukaryotes ( ) constitute the Domain (biology), domain of Eukaryota or Eukarya, organisms whose Cell (biology), cells have a membrane-bound cell nucleus, nucleus. All animals, plants, Fungus, fungi, seaweeds, and many unicellular organisms ...

forms of

alga Algae ( , ; : alga ) is an informal term for any organisms of a large and diverse group of photosynthetic organisms that are not plants, and includes species from multiple distinct clades. Such organisms range from unicellular microalgae, suc ...

e that includes marine,

freshwater Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. The term excludes seawater and brackish water, but it does include non-salty mi ...

and soil-living species. All eustigmatophytes are

unicellular A unicellular organism, also known as a single-celled organism, is an organism that consists of a single cell, unlike a multicellular organism that consists of multiple cells. Organisms fall into two general categories: prokaryotic organisms and ...

, with coccoid cells and

polysaccharide Polysaccharides (), or polycarbohydrates, are the most abundant carbohydrates found in food. They are long-chain polymeric carbohydrates composed of monosaccharide units bound together by glycosidic linkages. This carbohydrate can react with wat ...

cell walls. Eustigmatophytes contain one or more yellow-green

chloroplast A chloroplast () is a type of membrane-bound organelle, organelle known as a plastid that conducts photosynthesis mostly in plant cell, plant and algae, algal cells. Chloroplasts have a high concentration of chlorophyll pigments which captur ...

s, which contain

chlorophyll Chlorophyll is any of several related green pigments found in cyanobacteria and in the chloroplasts of algae and plants. Its name is derived from the Greek words (, "pale green") and (, "leaf"). Chlorophyll allows plants to absorb energy ...

a and the

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 vascular ("higher") plan ...

s violaxanthin and β-carotene. Eustigmatophyte zoids (

gamete A gamete ( ) is a Ploidy#Haploid and monoploid, haploid cell that fuses with another haploid cell during fertilization in organisms that Sexual reproduction, reproduce sexually. Gametes are an organism's reproductive cells, also referred to as s ...

s) possess a single or pair of

flagella A flagellum (; : flagella) (Latin for 'whip' or 'scourge') 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 pr ...

, originating from the

apex The apex is the highest point of something. The word may also refer to: Arts and media Fictional entities * Apex (comics) A-Bomb Abomination Absorbing Man Abraxas Abyss Abyss is the name of two characters appearing in Ameri ...

of the cell. Unlike other

heterokont The stramenopiles, also called heterokonts, are protists distinguished by the presence of stiff tripartite external hairs. In most species, the hairs are attached to flagella, in some they are attached to other areas of the cellular surface, an ...

ophytes, eustigmatophyte zoids do not have typical photoreceptive organelles (or eyespots); instead an orange-red eyespot outside a chloroplast is located at the anterior end of the zoid.

Ecologically Ecology () is the natural science of the relationships among living organisms and their environment. Ecology considers organisms at the individual, population, community, ecosystem, and biosphere levels. Ecology overlaps with the closely re ...

, eustigmatophytes occur as

photosynthetic Photosynthesis ( ) is a Biological system, system of biological processes by which Photoautotrophism, photosynthetic organisms, such as most plants, algae, and cyanobacteria, convert light energy, typically from sunlight, into the chemical ener ...

autotroph An autotroph is an organism that can convert Abiotic component, abiotic sources of energy into energy stored in organic compounds, which can be used by Heterotroph, other organisms. Autotrophs produce complex organic compounds (such as carbohy ...

s across a range of systems. Most eustigmatophyte genera live in freshwater or in soil, although ''

Nannochloropsis ''Nannochloropsis'' is a genus of algae comprising six known species. The genus in the current taxonomic classification was first termed by Hibberd (1981). The species have mostly been known from the marine environment but also occur in fresh and ...

'' contains marine species of picophytoplankton (2–4 μm). The class was erected to include some algae previously classified in the

Xanthophyceae Yellow-green algae or the Xanthophyceae (xanthophytes) are an important group of heterokont algae. Most live in fresh water, but some are found in marine and soil habitats. They vary from single-celled flagellates to simple colonial and filamen ...

Classification

* Class Eustigmatophyceae Hibberd & Leedale 1970 ** Order Eustigmatales Hibberd 1981 *** Genus '' Paraeustigmatos'' Fawley, Nemcová, & Fawley 2019 *** Family Eustigmataceae Hibberd 1981 hlorobothryaceae Pascher 1925; Pseudocharaciopsidaceae Lee & Bold ex Hibberd 1981**** Genus ?'' Ellipsoidion'' Pascher 1937 **** Genus '' Chlorobotrys'' Bohlin 1901 **** Genus '' Eustigmatos'' Hibberd 1981 **** Genus '' Pseudocharaciopsis'' Lee & Bold 1973 **** Genus '' Pseudostaurastrum'' Chodat 1921 **** Genus '' Vischeria'' Pascher 1938 - 16 spp. *** Family Monodopsidaceae Hibberd 1981 oboceae Hegewald 2007**** Genus '' Microchloropsis'' Fawley, Jameson & Fawley 2015 **** Genus '' Monodopsis'' Hibberd 1981 **** Genus ''

'' Hibberd 1981 **** Genus '' Pseudotetraedriella'' Hegewald & Padisák 2007 *** Family Neomonodaceae Amaral et al. 2020 **** Genus ?'' Botryochloropsis'' Preisig & Wilhelm 1989 **** Genus '' Characiopsiella'' Amaral et al. 2020 **** Genus '' Munda'' Amaral et al. 2020 **** Genus '' Neomonodus'' Amaral et al. 2020 **** Genus '' Pseudellipsoidion'' Neustupa & Nemková 2001 ** Order Goniochloridales Fawley, Elias & Fawley 2013 *** Family Goniochloridaceae **** Genus '' Goniochloris'' Geitler 1928 **** Genus '' Pseudostaurastrum'' Chodat 1921 **** Genus '' Tetraedriella'' Pascher 1930 **** Genus '' Trachydiscus'' H.Ettl 1964 **** Genus '' Vacuoliviride'' Nakayama et al. 2015

Phylogeny

Phylogeny of Eustigmatophyceae based on the work of Amaral et al 2020

References

Ochrophyta Eustigmatophyceae {{Heterokont-stub