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The cryptomonads 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 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. Some may exhibit mixotrophy. They are classified as clade Cryptomonada, which is divided into two classes: heterotrophic Goniomonadea and phototrophic Cryptophyceae. The two groups are united under three shared morphological characteristics: presence of a periplast, ejectisomes with secondary scroll, and mitochondrial cristae with flat tubules. Genetic studies as early as 1994 also supported the hypothesis that Goniomonas was sister to Cryptophyceae. A study in 2018 found strong evidence that the common ancestor of Cryptomonada was an autotrophic protist.
Cryptophyta is a group of single-celled flagellates. It contains a small group of heterotrophic flagellates known as katablepharids, as well as the abundant cryptomonads, which comprise the heterotrophic Goniomonadea and the photosynthetic Cryptophyceae. It is considered a division of algae among phycologists. It is alternatively known as Rollomonadia. Together with Palpitomonas and the Endohelea heliozoans, they compose the phylum Cryptista.
Chromista is a proposed but polyphyletic biological kingdom, refined from the Chromalveolata, consisting of single-celled and multicellular eukaryotic species that share similar features in their photosynthetic organelles (plastids). It includes all eukaryotes whose plastids contain chlorophyll c and are surrounded by four membranes. If the ancestor already possessed chloroplasts derived by endosymbiosis from red algae, all non-photosynthetic Chromista have secondarily lost the ability to photosynthesise. Its members might have arisen independently as separate evolutionary groups from the last eukaryotic common ancestor.
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 of lakes. The cells are usually brownish or greenish in color and are characteristic of having a slit-like furrow at the anterior. They are not known to produce any toxins. They are used to feed small zooplankton, which is the food source for small fish in fish farms. Many species of Cryptomonas can only be identified by DNA sequencing. Cryptomonas can be found in several marine ecosystems in Australia and South Korea.
The cryptophyceae are a class of algae, most of which have plastids. About 230 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.
In molecular biology, a twintron is an intron-within-intron excised by sequential splicing reactions. A twintron is presumably formed by the insertion of a mobile intron into an existing intron.
The raphidophytes, formally known as Raphidophycidae or Raphidophyceae, are a small group of eukaryotic algae that includes both marine and freshwater species. All raphidophytes are unicellular, with large cells, but no cell walls. Raphidophytes possess a pair of flagella, organised such that both originate from the same invagination. One flagellum points forwards, and is covered in hair-like mastigonemes, while the other points backwards across the cell surface, lying within a ventral groove. Raphidophytes contain numerous ellipsoid chloroplasts, which contain chlorophylls a, c1 and c2. They also make use of accessory pigments including β-carotene and diadinoxanthin. Unlike other heterokontophytes, raphidophytes do not possess the photoreceptive organelle typical of this group.
Pyrenomonas is a genus of cryptomonad.
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. Historically, Rhodomonas was characterized by its red chloroplast alone, but this no longer occurs as its taxonomy has become increasingly based on molecular and cellular data. Currently, there is some debate about the taxonomic validity of Rhodomonas as a genus and further research is needed to verify its taxonomic status. Rhodomonas is typically found in marine environments, although freshwater reports exist. It is commonly used as a live feed for various aquaculture species.
Geminigera /ˌdʒɛmɪnɪˈdʒɛɹə/ is a genus of cryptophyte from the family Geminigeraceae. Named for its unique pyrenoids, Geminigera is a genus with a single mixotrophic species. It was discovered in 1968 and is known for living in very cold temperatures such as under the Antarctic ice. While originally considered to be part of the genus Cryptomonas, the genus Geminigera was officially described in 1991 by D. R. A. Hill.
Guillardia is a genus of marine biflagellate cryptomonad algae with a plastid obtained through secondary endosymbiosis of a red alga.
Hemiselmis is a genus of cryptomonads.
The kathablepharids are a group of heterotrophic flagellates (Protists) the first species of which was described by Skuja in 1939 as Kathablepharis phoenikoston. His spelling was challenged because of non-compliance with botanical nomenclatural conditions, hence the alternative spelling Katablepharis. As the organism was heterotrophic and usually regarded as 'protozoan', and to favour stability, Skuja's original spelling has largely prevailed. With an anterior pocket and ejectisomes, the kathablepharids were thought initially to be cryptomonads. There were a variety of differences with Cryptomonas and other typical cryptomonads = cryptophytes, such as the thickness, length, and beat pattern of the flagella, their phagotrophic habitat, differences in the ejectisomes, and various features of their ultrastructure. The distinctive characteristics of the group were established from electron microscopical studies by Clay and Kugrens and Vørs. More recently they have been tentatively grouped with the chromalveolates, or distantly with the cryptophytes.
Mesodinium chamaeleon is a ciliate of the genus Mesodinium. It is known for being able to consume and maintain algae endosymbiotically for days before digesting the algae. It has the ability to eat red and green algae, and afterwards using the chlorophyll granules from the algae to generate energy, turning itself from being a heterotroph into an autotroph. The species was discovered in January 2012 outside the coast of Nivå, Denmark by professor Øjvind Moestrup.
Goniomonadea is a proposed class of cryptomonads which includes the orders Goniomonadida and Hemiarmida.
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 545.
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 Chroomonadaceae. Today, the family is generally recognized as sister to the Pyrenomonadaceae.
Cryptochrysis is a formerly recognized genus of cryptomonads first proposed by Adolf Pascher in 1911. He initially treated it as the sole genus in family Cryptochrysidaceae, but later treated it as a member of the Cryptochrysideae subfamily of Cryptomonadaceae, along with Rhodomonas, Chroomonas, and Cyanomonas. In 1967, R.W. Butcher relegated the group to a subgenus within Chroomonas.
Bjornbergiella hawaiiensis is a Hawaiian species of cryptomonad described in 1965. It is the sole member of the genus Bjornbergiella.
Rhinomonas fulva is a phytoplanktonic species of cryptomonad given its current designation in 1988.
References
- ↑ Novarino and Lucas (1993), "Some proposals for a new classification system of the Cryptophyceae", Botanical Journal of the Linnean Society, 111 (1): 3–21, doi:10.1006/bojl.1993.1002
- ↑ Bicudo (1965), "Bjornbergiella, a New Genus of Cryptophyceae from Hawaiian Soil", Phycologia, 5 (4): 217–221, doi:10.2216/i0031-8884-5-4-217.1