| Nephroselmis | |
|---|---|
 | |
| Nephroselmis olivacea | |
Scientific classification  | |
| Clade: | Viridiplantae |
| Division: | Chlorophyta |
| Class: | Nephrophyceae |
| Order: | Nephroselmidales |
| Family: | Nephroselmidaceae |
| Genus: | Nephroselmis Stein |
| Species | |
Nephroselmis is a genus of green algae. It has been placed in the family Nephroselmidaceae, [1] although a 2009 study suggests that it should be separated into its own class, Nephroselmidophyceae. [2] One species can be an endosymbiont of Hatena arenicola .
The cell body is right-left flattened. On the ventral side are two heterodynamic unequal flagella, the shorter beats towards the anterior direction while the long trails behind. Nephroselmis have a single cup-shaped chloroplast that contains an eyespot in its anterior-ventral edge below the short flagellum and a pyrenoid with starch plates. Vacuole is located in the left-anterior side, nucleus is located in the right-posterior side. The flagellar root system consists of a rhizoplast and three microtubular roots, one of which is multilayered. [3]
All the cells surface area is covered with layers of unminerallized scales, [4] while the surface of the flagella has hairs as well. [5] The cell body surface is covered by two to four layers of body scales. Flagella are covered with at least two scale layers, the second is characteristically rod-shaped. On top of that Nephroselmis has either a third layer of flagellar scales or flagellar pit scales. [3]
The scales morphology can be an important taxonomic characteristic for differentiating between the species. In the case of Nephroselmis spinosa, that exhibits some distinctive morphological characteristics, one of them is a unique outer scale type that has a spine that is extended for about 1μm, is slightly curved and has a hook shape at the end. [3]
A unique symbiosis occurs between the katablepharid Hatena arenicola and Nephroselmis rotunda. One of the interpretations to the observations of their interaction is that this symbiosis stage is leading to a secondary endosymbiosis, which will produce a completely new life form. [6]
This symbiosis is distinct from other reported cases of ongoing symbiosis in that the symbiont plastid is selectively enlarged up to ten times than the normal size. [6]
There is a possibility that retention of Nephroselmis-derived compartments is a precondition of the cell division process of H. arenicola, due to the fact that cell division was only observed in H. arenicola individuals after they have incorporated the N. rotunda parts into their cell body. [6]
The genus Nephroselmis according to reports and documentations done until 2009 appears to have global worldwide distribution. All species of Nephroselmis are marine inhabitants except for Nephroselmis olivacea which is found strictly in freshwater environments. [7]
The biofuel production potential of strains of Nephroselmis under certain treatments was examined in a research published in April 2022 concluding with - "isolated Nephroselmis sp. KGE2 is a candidate microalgal for biodiesel production using AMD as an iron source. The proposed process can be useful in overcoming the bottlenecks of microalgae cultivation. This can make the commercialization of biofuels economically feasible, and the products can be an alternative to fossil-derived commodities with zero carbon emissions." [8]
A research published in January 2021 reveals new information about the diversity of algal phago-mixotrophy - “Our experimental results demonstrate the occurrence of bacterivory across all of the prasinophyte strains tested, spanning three prasinophyte groups: the Pyramimonadophyceae, the Nephroselmidophyceae, and the Mamiellophyceae”. [9]
The life cycle that is found throughout the species of genus Nephroselmis is haplontic. [10]
Documented cell division of Nephroselmis astigmatica shows division by longitudinal binary fission. [11]
Observations of sexual reproduction in genus Nephroselmis are only known and were documented in the species Nephroselmis olivacea. [10] This species is also the only one in the genus that is known to be found in freshwater. [7] The sexual mating mechanism is isogamous heterothallic, The two gamete types are plus and minus, they are morphologically similar but have different roles during the mating process. The minus gamete attaches to the substratum, The plus gamete attaches to the dorsal side of the minus gamete by the base of the flagella of the plus gamete. [10]
Nephroselmis is monophyletic [7] and repeatedly appears in phylogenetic analysis results as an early divergent of the core chlorophytes. Therefore the genus is phylogenetically important to understand the early evolution of Chlorophyta.
According to a 2021 paper Nephroselmis appeared as one of the earliest branching clades from the core chlorophytes. Yet the relationships between Nephroselmis to its sister groups is yet to be resolved. "The three prasinophyte lineages Nephroselmis, Pycnococcus, and Picocystis (abbreviated NPP) branched as the closest relatives to the core chlorophytes", "The relationships between the NPP lineages are not fully resolved". [12]
Earlier paper published in 2011 showed similar results - "The class Nephroselmidophyceae is considered to be situated in the early radiation of Chlorophyta, but the strict phylogenetic position is uncertain". [13]
Family Nephroselmidaceae was put under the order Pseudoscourfieldiales, that consisted of it and Pseudoscourfieldiaceae. [7] The order Nephroselmidales was proposed in 2007- "The morphological evolution within the genus Nephroselmis is discussed and the order Nephroselmidales is proposed". [14]
Chlorophyta is a division of green algae informally called chlorophytes.
A flagellum is a hairlike 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 protists with flagella are known as flagellates.
Acetabularia is a genus of green algae in the family Polyphysaceae. Typically found in subtropical waters, Acetabularia is a single-celled organism, but gigantic in size and complex in form, making it an excellent model organism for studying cell biology. In form, the mature Acetabularia resembles the round leaves of a nasturtium, is 4 to 10 centimetres tall and has three anatomical parts: a bottom rhizoid that resembles a set of short roots; a long stalk in the middle; and a top umbrella of branches that may fuse into a cap. Unlike other giant unicellular organisms, which are multinucleate, members of this genus possess a single nucleus located in the rhizoid, which allows the cell to regenerate completely if its cap is removed. The caps of two Acetabularia may also be exchanged, even from two different species. In addition, if a piece of the stem is removed, with no access to the nucleus in the rhizoid, this isolated stem piece will also grow a new cap.
Sphaeropleales is an order of green algae that used to be called Chlorococcales. The order includes some of the most common freshwater planktonic algae such as Scenedesmus and Pediastrum. The Sphaeropleales includes vegetatively non-motile unicellular, colonial, or filamentous taxa. They have biflagellate zoospores with flagella that are directly opposed in direction : Sphaeroplea, Atractomorpha, Neochloris, Hydrodictyon, and Pediastrum. All of these taxa have basal body core connections. Motile cells generally lack cell walls or have only a very fine layer surrounding the cell membrane. Other common characteristics include a robust vegetative cell wall, cup-shaped chloroplasts with large pyrenoids, and relatively large nuclei.
Hatena arenicola is a species of single-celled eukaryotes discovered in 2000, and first reported in 2005. It was discovered by Japanese biologists Noriko Okamoto and Isao Inouye at the University of Tsukuba, and they gave the scientific description and formal name in 2006. The species is a flagellate, and can resemble a plant at one stage of its life, in which it carries a photosynthesizing alga inside itself, or an animal, acting as predator in another stage of its life. Researchers believe that this organism is in the process of secondary endosymbiosis, in which one organism is incorporated into another, resulting in a completely new life form.
The prasinophytes are a group of unicellular green algae. Prasinophytes mainly include marine planktonic species, as well as some freshwater representatives. The prasinophytes are morphologically diverse, including flagellates with one to eight flagella and non-motile (coccoid) unicells. The cells of many species are covered with organic body scales; others are naked. Well studied genera include Ostreococcus, considered to be the smallest free-living eukaryote, and Micromonas, both of which are found in marine waters worldwide. Prasinophytes have simple cellular structures, containing a single chloroplast and a single mitochondrion. The genomes are relatively small compared to other eukaryotes . At least one species, the Antarctic form Pyramimonas gelidicola, is capable of phagocytosis and is therefore a mixotrophic algae.
Chlorodendrales are an order of green, flagellated, thecate, unicellular eukaryotes, within the green algae class Chlorodendrophyceae. Prasinophyceae are defined by their cellular scales which are composed of carbohydrates, and Chlorodendrales are unique within this group due to these scales forming a fused thecal wall. Cells of Chlorodendrales are completely covered in scales, which fuse around the cell body producing the theca, but remain individually separated on the flagella, of which there are typically four per cell. Species within Chlorodendrales live in both marine and fresh water habitats, occupying both benthic and planktonic food webs. Additionally, they are photoautotrophs, meaning they produce their own food through the conversion of sunlight into chemical energy.
Eudorina is a paraphyletic genus in the volvocine green algae clade. Eudorina colonies consist of 16, 32 or 64 individual cells grouped together. Each individual cell contains flagella which allow the colony to move as a whole when the individual cells beat their flagella together. Description by GM Smith :
Atractomorpha is a genus in the Sphaeropleaceae, a family of green algae. The genus name is derived from Greek and means "spindle-shaped" or "arrow-shaped", and refers to the shape of the cells.
Carteria is a genus of green algae in the family Chlamydomonadaceae. Carteria are similar in morphology to the common genus Chlamydomonas and differ by having four, rather than two, flagella at the vegetative stage.
Crustomastix is a genus of green algae in the class Mamiellophyceae.
Picocystis is a monotypic genus of green algae, the sole species is Picocystis salinarum. It is placed within its own class, Picocystophyceae in the division Chlorophyta.
Trebouxia is a unicellular green alga. It is a photosynthetic organism that can exist in almost all habitats found in polar, tropical, and temperate regions. It can either exist in a symbiotic relationship with fungi in the form of lichen or it can survive independently as a free-living organism alone or in colonies. Trebouxia is the most common photobiont in extant lichens. It is a primary producer of marine, freshwater and terrestrial ecosystems. It uses carotenoids and chlorophyll a and b to harvest energy from the sun and provide nutrients to various animals and insects.
Trichosarcina is a genus of green algae in the order Ulotrichales. Filoprotococcus was once regarded as a synonym. However, Filoprotococcus is now considered valid in its own right. Trichosarcina is considered to be of uncertain validity.
The kathablepharids or katablepharids are a group of heterotrophic flagellates closely related to cryptomonads. First described by Heinrich Leonhards Skuja in 1939, kathablepharids were named after the genus Kathablepharis. This genus is corrected to Katablepharis under botanical nomenclature, but the original spelling is maintained under zoological nomenclature. They are single-celled protists with two anteriorly directed flagella, an anterior cytostome for ingesting eukaryotic prey, and a sheath that covers the cell membrane. They have extrusomes known as ejectisomes, as well as tubular mitochondrial cristae.
Pediastrum duplex is a species of fresh water green algae in the genus Pediastrum. It is the type species of the genus Pediastrum.
Richard Cawthorn Starr was an American phycologist.
Coolia is a marine dinoflagellate genus in the family Ostreopsidaceae. It was first described by Meunier in 1919. There are currently seven identified species distributed globally in tropical and temperate coastal waters. Coolia is a benthic or epiphytic type dinoflagellate: it can be found adhered to sediment or other organisms but it is not limited to these substrates. It can also be found in a freely motile form in the water column. The life cycle of Coolia involves an asexual stage where the cell divides by binary fission and a sexual stage where cysts are produced. Some of the species, for example, Coolia tropicalis and Coolia malayensis, produce toxins that can potentially cause shellfish poisoning in humans.
Lepidodinium is a genus of dinoflagellates belonging to the family Gymnodiniaceae. Lepidodinium is a genus of green dinoflagellates in the family Gymnodiniales. It contains two different species, Lepidodiniumchlorophorum and Lepidodinium viride. They are characterised by their green colour caused by a plastid derived from Pedinophyceae, a green algae group. This plastid has retained chlorophyll a and b, which is significant because it differs from the chlorophyll a and c usually observed in dinoflagellate peridinin plastids. They are the only known dinoflagellate genus to possess plastids derived from green algae. Lepidodinium chlorophorum is known to cause sea blooms, partially off the coast of France, which has dramatic ecological and economic consequences. Lepidodinium produces some of the highest volumes of Transparent Exopolymer Particles of any phytoplankton, which can contribute to bivalve death and the creation of anoxic conditions in blooms, as well as playing an important role in carbon cycling in the ocean.
Asterochloris is a genus of green algae in the family Trebouxiophyceae. It is a common photobiont in lichen, occurring in the thalli of more than 20 lichen genera worldwide. Asterochloris is distinguishable from the morphologically similar genus Trebouxia, primarily due to its deeply lobed chloroplast, the placement of the chloroplast along the cell's periphery before the initiation of zoospore or aplanospore formation, and its tendency to primarily reproduce asexually through the production of aplanospores.