The euglenoids (Euglenophyta) are a group of relatively small, eukaryotic, unicellular organisms, generally biflagellates, from aquatic or humid environments, with free-living or parasitic forms of various organisms, including humans. They are a large group of organisms when it comes to diversity..
They belong to the Protozoa kingdom and the Euglenozoa phylum. At present the phylum Euglenophyta is not taxonomically valid, however it is still widely used in the scientific community. Other names that this group receives are Discomitochondria (also in disuse) and excavated flagellates (common name).
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Euglenozoans are eukaryotic, unicellular organisms, not considered neither plants nor animals, but rather organisms that come from or descend from the first eukaryotic unicellular beings. Its main characteristics are:
They are small organisms, usually measuring between 15 to 40 micrometers, but there are species that can become much larger (500 micrometers). They present two flagella in most of the groups; one ventral directed towards the posterior region and another dorsal directed towards the anterior region.
Most are practically colorless, with the exception of those that have chloroplasts, which are capable of photosynthesis. Some have free life forms and others are parasites.
They have tubular organelles limited by membranes (extrusomes) and additionally have the peculiarity of presenting disc-shaped mitochondrial ridges.
They move through the use of their flagella or by euglenoid movements (metabolia), and present an ordered network of cytoskeletal filaments in the flagella (paraxial bars or rods), which distinguishes them from other taxonomic groups..
In the current classification the phyllum or Euglenophyta division is in disuse. This group was replaced by the phyllum Euglenozoa, which was erected by the prominent protozoologist Thomas Cavallier Smith in 1981, the same researcher who in 2016 proposed the new phylogeny and classification of the large taxa of euglenozoans..
The Euglenozoans are a fairly diverse group; are represented by 8 classes, 18 orders, 31 families and more than 1500 described species.
Euglenozoa reproduce exclusively asexually. Until now, sexual reproduction has not been observed or identified in these microorganisms. This asexual reproduction is carried out by cell division or bipartition, through closed mitosis.
This mitosis consists in that the genetic material (chromosomes) must separate within the nuclear membrane. For its part, the nuclear membrane does not disappear or regenerate (as in open mitosis), but is strangled to give rise to two or more nuclei. In general, this reproduction gives rise to 4 to 8 flagellate cells, which bear the name of zoospores..
These organisms exhibit complex feeding mechanisms and behaviors, of which the following are worth mentioning:
Autotrophic organisms are those that are capable of producing their food from inorganic compounds or substances. The most common example of autotrophic nutrition is photosynthesis, which is the transformation of inorganic substances into organic compounds thanks to the action of sunlight..
Among the euglenoids there are species with chloroplasts, which present chlorophyll to Y b like those of plants, indicating that these organisms can photosynthesize.
Heterotrophs are those organisms that obtain their food from another living being. Most Euglenozoa have a heterotrophic type of nutrition.
Some species feed on bacteria, algae, and detritus through phagocytosis, other species are parasites of various groups of aquatic animals and plants, causing serious diseases..
Mixotrophs are organisms capable of producing food through photosynthesis (for example) and from another living being. Some species of Euglenozoa that carry out photosynthesis have been observed feeding on other organisms, or on organic particles of moderate size..
A study determined that certain species of the genus Euglena, that photosynthesize under laboratory conditions, have lost their chloroplasts when deprived of light for long periods, changing their diet to heterotrophic.
Euglenozoans inhabit a wide variety of aquatic environments, such as lakes, streams, ponds, swamps, wet, marine, and estuarine environments..
There are some species of the group that have adapted to live as pelagic organisms in the water column, others live associated with the mud of very shallow aquatic environments, and others have developed adaptations such that they live as parasites in the circulatory system or in tissues. invertebrates and vertebrates.
Belonging to the class Eugenoidea, the Euglena they are one of the best known genera of the Euglenozoa. These organisms have heterotrophic, autotrophic and mixotrophic eating habits. They inhabit fresh and marine water bodies. Autotrophs are known to generate blooms or blooms that in some cases can become toxic.
The species Calkinsia aureus it is the only one of the genus, belonging to the Euglenoidea class. The organisms of this species are marine, free-living, without chloroplasts, so they are not capable of photosynthesis.
They feed on waste or dead organic matter of plant origin (saprophytes) and are facultative anaerobic, because they can live in environments with both the presence of oxygen and the absence of it..
They are a genus of euglenozoan parasites belonging to the Kinetoplastea class, which are capable of transmitting diseases to invertebrates and vertebrates. In humans they are the cause of serious diseases, such as sleeping sickness and Chagas disease..
Another genus of parasitic organisms belonging to the phyllum Euglenozoa and class Kinetoplastea. Species of this genus use mosquitoes as vectors to spread.
They are the organisms responsible for producing leishmaniasis, a disease that consists of the appearance of one or more volcano-shaped skin papules, which appear approximately one month after the bite of the infected mosquito. This disease mainly attacks mammals, including humans.
It is a genus of euglenozoans of the class Diplonemea. At least five species are known, they are present in both fresh and marine water. Most are free-living organisms, however there are reports of infections in algae and bivalve molluscs caused by species of this genus..
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