Cryptomonad

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Cryptomonad

The cryptomonads are a small group of flagellate

Flagellate

Flagellates are cell s with one or more whip-like organelles called flagellum. Some cells in animals may be flagellate, for instance the spermatozoa of most phyla....
s, most of which have chloroplast

Chloroplast

Chloroplasts are organelles found in plant cells and other eukaryote organisms that conduct photosynthesis. Chloroplasts capture light energy to conserve Thermodynamic free energy in the form of Adenosine triphosphate and reduce NADP to NADPH through a complex set of processes called photosynthesis....
s. They are common in freshwater, and also occur in marine and brackish habitats. Each cell is around 10-50 µm

1 E-5 m

To help compare different orders of magnitude, this page lists lengths between 10−5 metre and 10−4 m .1 E-6 m...
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

Flagellum

A flagellum is a tail-like structure that projects from the cell body of certain prokaryotic and eukaryotic cells, and it functions in locomotion....
.

Cryptomonads distinguished by the presence of characteristic extrusome

Extrusome

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The cryptomonads are a small group of flagellate

Flagellate

Chloroplast

1 E-5 m

Flagellum

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....
s called 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 ejectisomes, visible under the light microscope, are associated with the pocket; smaller ones occur elsewhere on the cell.

Cryptomonads have one or two chloroplasts, except for Chilomonas which has leucoplast

Leucoplast

Leucoplasts 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....
s and Goniomonas which lacks plastids entirely. These contain chlorophyll

Chlorophyll

Chlorophyll is a green pigment found in most plants, algae, and cyanobacteria. Its name is derived from Greek language: ?????? and f????? ....
s a and c, together with phycobiliprotein

Phycobiliprotein

Phycobiliproteins are water-soluble proteins present in cyanobacteria and certain algae that capture light energy which is then passed on to chlorophylls during photosynthesis....
s and other pigments, and vary in color from brown to green. Each is surrounded by four membranes, and there is a reduced cell nucleus

Cell nucleus

In cell biology, the nucleus , also sometimes referred to as the "control center", is a membrane-enclosed organelle found in all eukaryote cell ....
called a nucleomorph

Nucleomorph

Nucleomorphs are small, reduced eukaryotic nuclei found in certain plastids. So far, only two groups of organisms are known to contain a nucleomorph: the cryptomonads of the supergroup Chromista and the chlorarachniophytes of the supergroup Rhizaria....
between the middle two. This indicates that the chloroplast was derived from a eukaryotic

Eukaryote

Animals, plants, fungus, and protists are eukaryotes , organisms whose Cell are organized into complex structures enclosed within Cell membrane....
symbiont, shown by genetic studies to have been a red alga.

A few cryptomonads, such as Cryptomonas
Cryptomonas

Cryptomonas is the name-giving genus of the cryptomonads. It is common in freshwater habitats and often forms blooms in greater depths of lakes, or during winter beneath the ice....
, can form palmelloid stages, but readily escape the surrounding mucus to become free-living flagellates again. Cryptomonad flagella are inserted parallel to one another, and are covered by bipartite hairs called mastigonemes

Mastigonemes

Mastigonemes are Anatomical terms of location "hairs" found covering the flagellum of heterokont and Cryptomonad algae. They are approximately 15 nanometre in diameter, and usually consist of a tubular shaft that itself terminates in smaller "hairs"....
, formed within the endoplasmic reticulum

Endoplasmic reticulum

The endoplasmic reticulum is a eukaryote organelle that forms an interconnected network of tubules, vesicle , and cisternae within cell . The lacey membranes of the endoplasmic reticulum were first seen by Keith R....
and transported to the cell surface. Small scales may also be present on the flagella and cell body. The mitochondria

Mitochondrion

In cell biology, a mitochondrion is a membrane-enclosed organelle found in most eukaryote cell . These organelles range from 0.5–10 micrometers in diameter....
have flat crista

Crista

Cristae are the internal compartments formed by the Inner mitochondrial membrane of a mitochondrion. They are studded with proteins, including ATP synthase and a variety of cytochromes....
e, and mitosis

Mitosis

Mitosis is the process in which a eukaryotic cell separates the chromosomes in its cell nucleus, into two identical sets in two daughter nuclei....
is open; sexual reproduction

Sexual reproduction

Sexual reproduction is characterized by processes that pass a Genetic recombination of Genetics material to offspring, resulting in Genetic diversity....
has also been reported.

Originally the cryptomonads were considered close relatives of the dinoflagellate

Dinoflagellate

The dinoflagellates are a large group of flagellate protists. Most are marine plankton, but they are common in fresh water habitats as well. Their populations are distributed depending on sea surface temperature, salinity, or depth....
s because of their similar pigmentation. Later botanists treated them as a separate division, Cryptophyta, while zoologists treated them as the flagellate order Cryptomonadida. There is considerable evidence that cryptomonad chloroplasts are closely related to those of the heterokont

Heterokont

The heterokonts or stramenopiles are a major line of eukaryotes presently containing about 10,500 known species. Most are algae, ranging from the giant multicellular kelp to the unicellular diatoms, which are a primary component of plankton....
s and haptophyte

Haptophyte

The haptophytes, classed either as the Prymnesiophyta or Haptophyta, are a phylum of algae. The chloroplasts are pigmented similarly to those of the heterokonts, such as golden algae, but the structure of the rest of the cell is different, so it may be that they are a separate line whose chloroplasts are derived from similar endosymbionts....
s, and the three groups are sometimes united as the Chromista

Chromista

The Chromista are a eukaryote supergroup, probably polyphyletic, which may be treated as a separate kingdom or included among the Protista. They include all algae whose chloroplasts contain chlorophylls a and c, as well as various colorless forms that are closely related to them....
. However, the case that the organisms themselves are closely related is not very strong, and they may have acquired chloroplasts independently.

Katablepharids

The katablepharids, a group of heterotrophic flagellate

Flagellate

Flagellates are cell s with one or more whip-like organelles called flagellum. Some cells in animals may be flagellate, for instance the spermatozoa of most phyla....
s, have been considered as part of the Cryptophyta since katablepharids were described in 1939. Although they differ from other cryptophytes and have even been proposed to be alveolate

Alveolate

The alveolates are a major line of protists....
s, early 21st century research suggests they are related to cryptophytes.

Cryptomonad

Katablepharids

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