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 micr ...

, 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 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 fro ...

. 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 extrusomes called ejectosomes 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 cryptophyte-specific cell surrounding. Except for '' Chilomonas'', which has leucoplasts, cryptophytes have one or two chloroplasts. These contain

chlorophyll Chlorophyll (also chlorophyl) 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 allow plants to ...

s ''a'' and ''c'', together with

phycobiliprotein Phycobiliproteins are water-soluble proteins present in cyanobacteria and certain algae ( rhodophytes, cryptomonads, glaucocystophytes). They capture light energy, which is then passed on to chlorophylls during photosynthesis. Phycobiliproteins ...

s 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 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. 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. 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 cysts–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, formed within the

endoplasmic reticulum The endoplasmic reticulum (ER) is, in essence, the transportation system of the eukaryotic cell, and has many other important functions such as protein folding. It is a type of organelle made up of two subunits – rough 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 cells of most Eukaryotes, such as animals, plants and fungi. Mitochondria have a double membrane structure and use aerobic respiration to generate adenosine triphosphate (ATP), which is used ...

have flat

crista A crista (; plural cristae) is a fold in the inner membrane of a mitochondrion. The name is from the Latin for ''crest'' or ''plume'', and it gives the inner membrane its characteristic wrinkled shape, providing a large amount of surface area fo ...

e, 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 maintai ...

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 th ...

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 naturalist, zoologist, comparative anatomist, geologist, and microscopist. Ehrenberg was an evangelist and was considered to be of the most famous and productive scient ...

in 1831, while studying Infusoria. Later, botanists treated them as a separate

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

flagellate A flagellate is a cell or organism with one or more whip-like appendages called flagella. The word ''flagellate'' also describes a particular construction (or level of organization) characteristic of many prokaryotes and eukaryotes and thei ...

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

dinoflagellate 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 ...

s because of their (seemingly) similar pigmentation, being grouped as the Pyrrhophyta. 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 a ...

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. 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 ...

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

'', (2) '' Chroomonas/ Komma'' and '' Hemiselmis'', (3) '' Rhodomonas/

Rhinomonas ''Rhinomonas'' is a genus of cryptophytes. It includes the species ''Rhinomonas pauca''. References Cryptomonad genera {{Cryptomonad-stub ...

Storeatula ''Storeatula'' is a genus of cryptophytes. It includes the species In biology, a species is the basic unit of Taxonomy (biology), classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often de ...

'', (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 of cryptophytes containing the five genera '' Geminigera'', '' Guillardia'', ''Hanusia'', ''Proteomonas'' and ''Teleaulax''. They are characterised by chloroplasts containing Cr-phycoerythrin 545, and an inner peripla ...

'', (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 peripla ...

'', (6) ''

Proteomonas sulcata 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 periplast ...

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

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 cel ...

'' Bicudo 1966 **** Genus '' Tetragonidium'' Pascher 1914 ** Order Pyrenomonadales 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 Chroom ...

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 '' Chroomonas'' Hansgirg 1885 **** Genus ''Falcomonas'' Hill 1991 **** Genus '' Hemiselmis'' Parke 1949 **** Genus ''Komma (alga), Komma'' Hill 1991 **** Genus '' Nodeana'' Skvortzov 1968 **** Genus '' Planonephros'' Christensen 1978 **** Genus '' Protochrysis'' Pascher 1911 *** Family

Geminigeraceae 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 periplast ...

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 ''Rhinomonas'' is a genus of cryptophytes. It includes the species ''Rhinomonas pauca''. References Cryptomonad genera {{Cryptomonad-stub ...

'' Hill & Wetherbee 1988 **** Genus '' Rhodomonas'' Karsten 1898 'Pyrenomonas''_Santore_1984.html" ;"title="Pyrenomonas.html" ;"title="'Pyrenomonas">'Pyrenomonas'' Santore 1984">Pyrenomonas.html" ;"title="'Pyrenomonas">'Pyrenomonas'' Santore 1984**** Genus ''

'' 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 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 aro ...

Pascher 1967 **** Genus '' Calkinsiella'' Skvortzov 1969 **** Genus '' Hillea'' Schiller 1925 *** Family ? Pleuromastigaceae 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 of Cryptophyta The cryptophyceae are a class of algae, most of which have plastids. About 220 species are known, and they are common in f ...

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