The cryptophyceae are a class of

algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mic ...

, most of which have

plastids The plastid (Greek: πλαστός; plastós: formed, molded – plural plastids) is a membrane-bound organelle found in the cells of plants, algae, and some other eukaryotic organisms. They are considered to be intracellular endosymbiotic cyanobac ...

. About 220 species are known, and 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 A flagellum (; ) is a hairlike appendage that protrudes from certain plant and animal sperm cells, and from a wide range of microorganisms to provide motility. Many protists with flagella are termed as flagellates. A microorganism may have f ...

. Some exhibit

mixotrophy A mixotroph is an organism that can use a mix of different sources of energy and carbon, instead of having a single trophic mode on the continuum from complete autotrophy at one end to heterotrophy at the other. It is estimated that mixotrophs comp ...

Characteristics

Cryptophytes are distinguished by the presence of characteristic

extrusome 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. Notable extru ...

s called

ejectosome An ejectosome is a cellular organelle responsible for ejecting their contents from the cell. Two unrelated types of ejectosomes are described in the literature: # Cryptomonads have two types of characteristic ejectosomes known as extrusomes. # Int ...

s or ejectisomes, which consist of two connected spiral ribbons held under tension. If the cells are irritated either by mechanical, chemical or light stress, they discharge, propelling the cell in a zig-zag course away from the disturbance. Large ejectosomes, visible under the light microscope, are associated with the pocket; smaller ones occur underneath the

periplast The periplast is one of three types of cell-covering of three classes of algae. The ''Cryptomonads'' have the periplast covering. The '' Dinophyceae'' have a type called the amphiesma, and the ''Euglena'' covering is the pellicle. Structure The pe ...

, the cryptophyte-specific cell surrounding. Except for ''

Chilomonas ''Chilomonas'' is a genus of cryptophytes, including the species '' Chilomonas paramecium''. Chilomonas is a protozoa (heterotroph). Chilomonas is golden brown and has two flagella A flagellum (; ) is a hairlike appendage that protrudes fr ...

'', which has

leucoplast Leucoplasts (λευκός leukós "white", πλαστός plastós "formed, molded") are a category of plastid and as such are organelles found in plant cells. They are non-pigmented, in contrast to other plastids such as the chloroplast. Lacki ...

s, cryptophytes have one or two chloroplasts. These contain chlorophylls ''a'' and ''c'', together with phycobiliproteins and other pigments, and vary in color (brown, red to blueish-green). Each is surrounded by four membranes, and there is a reduced

cell nucleus The cell nucleus (pl. nuclei; from Latin or , meaning ''kernel'' or ''seed'') is a membrane-bound organelle found in eukaryotic cells. Eukaryotic cells usually have a single nucleus, but a few cell types, such as mammalian red blood cells, h ...

called a

nucleomorph Nucleomorphs are small, vestigial eukaryotic nuclei found between the inner and outer pairs of membranes in certain plastids. They are thought to be vestiges of primitive red and green algal nuclei that were engulfed by a larger eukaryote. Becaus ...

between the middle two. This indicates that the plastid was derived from a

eukaryotic Eukaryotes () are organisms whose cells have a nucleus. All animals, plants, fungi, and many unicellular organisms, are Eukaryotes. They belong to the group of organisms Eukaryota or Eukarya, which is one of the three domains of life. Bacte ...

symbiont, shown by genetic studies to have been a

red alga Red algae, or Rhodophyta (, ; ), are one of the oldest groups of eukaryotic algae. The Rhodophyta also comprises one of the largest phyla of algae, containing over 7,000 currently recognized species with taxonomic revisions ongoing. The majority ...

. However, the plastids are very different from red algal plastids: phycobiliproteins are present but only in the thylakoid lumen and are present only as phycoerythrin or

phycocyanin Phycocyanin is a pigment-protein complex from the light-harvesting phycobiliprotein family, along with allophycocyanin and phycoerythrin. It is an accessory pigment to chlorophyll. All phycobiliproteins are water-soluble, so they cannot exist w ...

. In the case of "Rhodomonas" the crystal structure has been determined to 1.63Å; and it has been shown that the alpha subunit bears no relation to any other known phycobiliprotein. A few cryptophytes, such as ''

Cryptomonas ''Cryptomonas'' is the name-giving genus of the Cryptomonads established by German biologist Christian Gottfried Ehrenberg in 1831. The algae are common in freshwater habitats and brackish water worldwide and often form blooms in greater depths ...

'', can form palmelloid stages, but readily escape the surrounding mucus to become free-living flagellates again. Some ''Cryptomonas'' species may also form immotile

microbial cyst A microbial cyst is a resting or dormant stage of a microorganism, usually a bacterium or a protist or rarely an invertebrate animal, that helps the organism to survive in unfavorable environmental conditions. It can be thought of as a state of ...

s–resting stages with rigid cell walls to survive unfavorable conditions. Cryptophyte flagella are inserted parallel to one another, and are covered by bipartite hairs called

mastigonemes Mastigonemes are lateral "hairs" that attach to protistan flagella. Flimsy hairs attach to the flagella of euglenid flagellates, while stiff hairs occur in stramenopile and cryptophyte protists.Hoek, C. van den, Mann, D. G. and Jahns, H. M. ( ...

, formed within the endoplasmic reticulum and transported to the cell surface. Small scales may also be present on the flagella and cell body. The

mitochondria A mitochondrion (; ) is an organelle found in the Cell (biology), cells of most Eukaryotes, such as animals, plants and Fungus, fungi. Mitochondria have a double lipid bilayer, membrane structure and use aerobic respiration to generate adenosi ...

have flat cristae, and

mitosis In cell biology, mitosis () is a part of the cell cycle in which replicated chromosomes are separated into two new nuclei. Cell division by mitosis gives rise to genetically identical cells in which the total number of chromosomes is mainta ...

is open;

sexual reproduction Sexual reproduction is a type of reproduction that involves a complex life cycle in which a gamete ( haploid reproductive cells, such as a sperm or egg cell) with a single set of chromosomes combines with another gamete to produce a zygote tha ...

has also been reported. The group have evolved a whole range of light-absorbing pigments, called phycobilins, which are able to absorb wavelengths that are not accessible to other plants or algae, allowing them to live in a variety of different ecological niches. While cryptophytes are usually seen as asexual, sexual reproductions do occur; both haploid and diploid forms have been found. The two species ''Teleaulax amphioxeia'' and ''Plagioselmis prolonga'' are now considered to be the same species, where ''T. amphioxeia'' is the diploid form and ''P. prolonga'' is the haploid form. The diploid form is most common when there are more nutrients in the water. Two haploid cells will often fuse to form a diploid cell, mixing their genes.

Classification

CSIRO ScienceImage 7234 microalgal cultures

The first mention of cryptophytes appears to have been made by

Christian Gottfried Ehrenberg Christian Gottfried Ehrenberg (19 April 1795 – 27 June 1876) was a German Natural history, naturalist, zoologist, comparative anatomist, geologist, and microscopy, microscopist. Ehrenberg was an Evangelicalism, evangelist and was considered to ...

in 1831, while studying

Infusoria Infusoria are minute freshwater life forms including ciliates, euglenoids, protozoa, unicellular algae and small invertebrates. Some authors (e.g., Bütschli) used the term as a synonym for Ciliophora. In modern formal classifications, the term ...

. Later, botanists treated them as a separate

group, class Cryptophyceae or division Cryptophyta, while zoologists treated them as the flagellate

protozoa Protozoa (singular: protozoan or protozoon; alternative plural: protozoans) are a group of single-celled eukaryotes, either free-living or parasitic, that feed on organic matter such as other microorganisms or organic tissues and debris. Histo ...

order Cryptomonadina. In some classifications, the cryptomonads were considered close relatives of the dinoflagellates because of their (seemingly) similar pigmentation, being grouped as the

Pyrrhophyta The dinoflagellates (Greek δῖνος ''dinos'' "whirling" and Latin ''flagellum'' "whip, scourge") are a monophyletic group of single-celled eukaryotes constituting the phylum Dinoflagellata and are usually considered algae. Dinoflagellates are ...

. There is considerable evidence that cryptophyte chloroplasts are closely related to those of the

heterokont Heterokonts are a group of protists (formally referred to as Heterokonta, Heterokontae or Heterokontophyta). The group is a major line of eukaryotes. Most are algae, ranging from the giant multicellular kelp to the unicellular diatoms, which ...

s and

haptophyte The haptophytes, classified either as the Haptophyta, Haptophytina or Prymnesiophyta (named for '' Prymnesium''), are a clade of algae. The names Haptophyceae or Prymnesiophyceae are sometimes used instead. This ending implies classification at ...

s, and the three groups are sometimes united as the

Chromista Chromista is a biological kingdom consisting of single-celled and multicellular eukaryotic species that share similar features in their photosynthetic organelles ( plastids). It includes all protists whose plastids contain chlorophyll ''c'', ...

. However, the case that the organisms themselves are closely related is not very strong, and they may have acquired plastids independently. Currently they are discussed to be members of the clade

Diaphoretickes Diaphoretickes () is a major group of eukaryotic organisms, with over 400,000 species. The majority of the earth's biomass that carries out photosynthesis belongs to Diaphoretickes. Diaphoretickes includes: * Archaeplastida (comprising red alg ...

and to form together with the

Haptophyta The haptophytes, classified either as the Haptophyta, Haptophytina or Prymnesiophyta (named for '' Prymnesium''), are a clade of algae. The names Haptophyceae or Prymnesiophyceae are sometimes used instead. This ending implies classification at ...

the group

Hacrobia The cryptomonads-haptophytes assemblage is a proposed monophyletic grouping of unicellular eukaryotes that are not included in the SAR supergroup. Several alternative names have been used for the group, including Hacrobia (derived from "ha-" refe ...

. Parfrey et al. and Burki et al. placed Cryptophyceae as a sister clade to the

Green Algae The green algae (singular: green alga) are a group consisting of the Prasinodermophyta and its unnamed sister which contains the Chlorophyta and Charophyta/Streptophyta. The land plants (Embryophytes) have emerged deep in the Charophyte alga as ...

. One suggested grouping is as follows: (1) ''

'', (2) ''

Chroomonas ''Chroomonas'' is a genus of Cryptomonad, cryptophytes first described by Anton Hansgirg. It includes the species ''Chroomonas elegans'', ''Chroomonas placoidea'', ''Chroomonas baltica'', ''Chroomonas guttula'' and ''Chroomonas vectensis''. Refe ...

/ Komma'' and ''

Hemiselmis ''Hemiselmis'' is a genus of cryptomonads. History of discovery It was first described by English biologist Mary Parke in 1949. She also described the first species in this genus, ''Hemiselmis rufescens.'' Morphology ''Hemiselmis'' are typi ...

'', (3) ''

Rhodomonas ''Rhodomonas'' is a genus of cryptomonads. It is characterized by its red colour, the square-shaped plates of its inner periplast, its short furrow ending in a gullet, and a distinctly shaped chloroplast closely associated with its nucleomorph. Hi ...

/ Rhinomonas/ Storeatula'', (4) ''

Guillardia ''Guillardia'' is a genus of flagellate cryptomonad algae belonging to the family Geminigeraceae, containing a secondary plastid within a reduced cytoplasmic compartment that contains a vestigial nucleomorph. There is only one characterised mem ...

Hanusia Geminigeraceae is a family (biology), family of Cryptomonad, cryptophytes containing the five genera ''Geminigera'', ''Guillardia'', ''Hanusia'', ''Proteomonas'' and ''Teleaulax''. They are characterised by chloroplasts containing Phycoerythrin, ...

'', (5) ''

Geminigera ''Geminigera'' /ˌdʒɛmɪnɪˈdʒɛɹə/ is a genus of cryptophyte from the family Geminigeraceae. Named for its unique pyrenoid Pyrenoids are sub-cellular micro-compartments found in chloroplasts of many algae,Giordano, M., Beardall, J., ...

Plagioselmis ''Plagioselmis'' is a genus of cryptophytes, including the species '' Plagioselmis punctata''. ''Plagioselmis'' was first described by Butcher in 1967 as a saltwater life form. In 1994, Novarino placed the freshwater ''Rhodomonas minuta'' into ...

Teleaulax Geminigeraceae is a family of cryptophytes containing the five genera '' Geminigera'', '' Guillardia'', ''Hanusia'', ''Proteomonas'' and ''Teleaulax''. They are characterised by chloroplasts containing Cr-phycoerythrin 545, and an inner peripl ...

'', (6) '' Proteomonas sulcata'', (7) '' Falcomonas daucoides''. * Class Cryptophyceae Fritsch 1937 ryptomonadea Stein 1878 emend. Schoenichen 1925** Genus '' Wysotzkia'' Lemmermann 1899 ** Genus '' Urgorri'' Laza-Martinez 2012 ** Order

Tetragonidiales Tetragonidiaceae is a family of cryptomonads which includes two genera. Members of Tetragonidiaceae are distinguished from other cryptomonads by reproduction occurring in a non-motile vegetative phase, as well as the formation of multicellular f ...

Kristiansen 1992 *** Family

Tetragonidiaceae Tetragonidiaceae is a family of cryptomonads The cryptomonads (or cryptophytes) are a group of algae, most of which have plastids. They are common in freshwater, and also occur in marine and brackish habitats. Each cell is around 10–50 μ ...

Bourelly ex Silva1980 **** Genus ''

Bjornbergiella ''Bjornbergiella hawaiiensis'' is a Hawaiian species of cryptomonad The cryptomonads (or cryptophytes) are a group of algae, most of which have plastids. They are common in freshwater, and also occur in marine and brackish habitats. Each ce ...

'' Bicudo 1966 **** Genus '' Tetragonidium'' Pascher 1914 ** Order

Pyrenomonadales Pyrenomonadales is an order of Cryptophyta The cryptophyceae are a class of algae, most of which have plastids. About 220 species are known, and they are common in freshwater, and also occur in marine and brackish habitats. Each cell is arou ...

Novarino & Lucas 1993 *** Family Baffinellaceae Daugbjerg & Norlin 2018 **** Genus '' Baffinella'' Norlin & Daugbjerg 2018 *** Family

Chroomonadaceae Chroomonadaceae is a family of cryptomonads first recognized by Clay et al in 1999 as including genera ''Chroomonas'', '' Falcomonas'', and '' Komma''. Following a molecular phylogenic study in 2002, Hemiselmis was also placed within the Chroomon ...

Clay, Cugrens & Lee 1999 **** Genus ?'' Smithimastix'' Skvortzov 1969 'Smithiella''_Skvortzov_1968_nom._illeg..html" ;"title="Smithiella.html" ;"title="'Smithiella">'Smithiella'' Skvortzov 1968 nom. illeg.">Smithiella.html" ;"title="'Smithiella">'Smithiella'' Skvortzov 1968 nom. illeg.**** Genus ''

'' Hansgirg 1885 **** Genus ''Falcomonas'' Hill 1991 **** Genus ''

'' Parke 1949 **** Genus '' Komma'' Hill 1991 **** Genus '' Nodeana'' Skvortzov 1968 **** Genus '' Planonephros'' Christensen 1978 **** Genus '' Protochrysis'' Pascher 1911 *** Family Geminigeraceae Clay, Cugrens & Lee 1999 **** Genus ''

'' Hill 1991 **** Genus ''

'' Hill & Wetherbee 1990 **** Genus '' Phia'' Özdikmen 2009 [''

'' Deane et al. 1998 non Cripps 1989] **** Genus ''

'' Butcher 1967 ex Novarino, Lucas & Morrall 1994 **** Genus ''

'' Hill 1991 *** Family

Pyrenomonadaceae Pyrenomonadaceae is a family of cryptomonads which includes three or four known genera. They are distinguished from other cryptomonads by their nucleomorphs being imbedded into the pyrenoid, and the presence of distinctive pigment phycoerythrin ...

Novarino & Lucas 1993 **** Genus '' Proteomonas'' Hill & Wetherbee 1986 **** Genus '' Rhinomonas'' Hill & Wetherbee 1988 **** Genus ''

'' Karsten 1898 'Pyrenomonas''_Santore_1984.html" ;"title="Pyrenomonas.html" ;"title="'Pyrenomonas">'Pyrenomonas'' Santore 1984">Pyrenomonas.html" ;"title="'Pyrenomonas">'Pyrenomonas'' Santore 1984**** Genus '' Storeatula'' Hill 1991 ** Order Cryptomonadales Pascher 1913 *** Family ?Butschliellaceae Skvortzov 1968 **** Genus ''Butschliella'' Skvortzov 1968 **** Genus ''Skvortzoviella'' Bourelly 1970 *** Family ? Cyathomonadaceae Pringsheim 1944 **** Genus '' Cyathomonas'' de Fromentel 1874 *** Family ?

Hilleaceae ''Hilleaceae'' was one of the three families of Cryptomonads proposed by R.W. Butcher in 1967, who included only the genus '' Hillea''. It has appeared in at least two other cryptomonad classification systems since then. However, as ''Hillea'' ...

Pascher 1967 **** Genus '' Calkinsiella'' Skvortzov 1969 **** Genus '' Hillea'' Schiller 1925 *** Family ?

Pleuromastigaceae Pleuromastigaceae is an obsolete family of cryptomonads, which included genera '' Monomastix'', '' Pleuromastix'', and '' Xanthodiscus''. Today, Monomastix is regarded as a green alga, and since 1987 Xanthodiscus is regarded as a synonym of ...

Bourrelly ex Silva 1980 **** Genus ?'' Opisthostigma'' Scherfffel 1911 **** Genus '' Pleuromastix'' Scherffel 1912 non Namyslowski 1913 **** Genus '' Xanthodiscus'' Schewiakoff 1892 *** Family

Cryptomonadaceae Cryptomonadaceae is a family of Cryptophyta in the order Cryptomonadales Cryptomonadales is an Order (biology), order of Cryptomonad, Cryptophyta containing the families Cryptomonadaceae and Hilleaceae. References Cryptomonads Bikont ord ...

Ehrenberg 1831 ampylomonadaceae Clay, Kugrens & Lee 1999; Cryptochrysidaceae Pascher 1931] **** Genus ?''

'' Ehrenberg 1831 **** Genus ?'' Protocryptochrysis'' Skvortzov 1969 **** Genus ''

Cryptella ''Cryptella'' is a genus of small-shelled slugs in the family Parmacellidae. Species Species in the genus ''Cryptella'' include: * '' Cryptella alegranzae'' Hutterer & Groh, 1991

'' Pascher 1929 **** Genus ''

Cryptochloris ''Cryptochloris'' is a genus of golden mole Golden moles are small insectivorous burrowing mammals endemic to Sub-Saharan Africa. They comprise the family Chrysochloridae and as such they are taxonomically distinct from the true moles, fami ...

'' Schiller 1925 **** Genus '' Cryptochrysis'' Pascher 1911 **** Genus ''

'' Ehrenberg 1832 'Campylomonas''_Hill_1991.html" ;"title="Campylomonas.html" ;"title="' 'Campylomonas''_Hill_1991">Campylomonas.html"_;"title="'Campylomonas">'Campylomonas''_Hill_1991****_Genus_''Cyanomastix.html" ;"title="Campylomonas">'Campylomonas'' Hill 1991">Campylomonas.html" ;"title="'Campylomonas">'Campylomonas'' Hill 1991**** Genus ''Cyanomastix">Campylomonas">'Campylomonas'' Hill 1991">Campylomonas.html" ;"title="'Campylomonas">'Campylomonas'' Hill 1991**** Genus ''Cyanomastix'' Lackey 1936 **** Genus ''Isoselmis'' Butcher 1967 **** Genus ''Kisselevia'' Skvortzov 1969 **** Genus ''Meyeriella'' Skvortzov 1968 **** Genus ''Olivamonas'' Skvortzov 1969 **** Genus '' Protocryptomonas'' Skvortzov 1969 ex Bicudo 1989

References

External links

Tree of Life: Cryptomonads
{{Taxonbar, from=Q21281984, from2=Q18668642, from3=Q488032 Taxa named by Thomas Cavalier-Smith