| Euglena viridis | |
|---|---|
 | |
Scientific classification | |
| Domain: | Eukaryota |
| Clade: | Discoba |
| Phylum: | Euglenozoa |
| Class: | Euglenida |
| Clade: | Euglenophyceae |
| Order: | Euglenales |
| Family: | Euglenaceae |
| Genus: | Euglena |
| Species: | E. viridis |
| Binomial name | |
| Euglena viridis (O.F.Müller)Ehrenberg | |
Euglena viridis is a single-celled species ofeuglenoid, a type ofmicroalgae. It is one of the oldest-known species ofEuglena, and was first seen byAntonie van Leeuwenhoek in 1764.[1] It is found infreshwater habitats worldwide.[2]
Euglena viridis, along with otherEuglena species, are well-studied.[3] Cells ofE. viridis have asecondary chloroplast.[4] Thechloroplast is bounded by three layers of membrane without anucleomorph.[3]
Euglena viridis is one of the firstEuglena species named whenEhrenberg established thegenusEuglena.[3]Euglena viridis is also thetype species of this genus.[2]
The whole group ofEuglenozoa was originally placed in a group calledExcavata. However, Excavata has been thought notmonophyletic and is divided into several groups. Now, Euglenozoa is placed below a group in Discoba.[5]
According to molecular evidence, phylogenetic relationships betweenEuglena viridis and its close relatives are as follows:[6]
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Thephylogenetic trees of theEuglena genus still have someclades withpolytomy. The phylogenetic relationship ofEuglena viridis with otherEuglena species is still unclear until 2017.[3]
Euglena viridis consists of single cells with twoflagella, although one flagellum is very reduced and so only one is visible under the microscope. Normally, it is 40–65 μm long, slightly bigger than other well-knownEuglena species:Euglena gracilis.[7] The cells are narrowly or widely spindle-shaped, rounded at the anterior end and pointed at the posterior end. The cell is surrounded bypellicle, which has faint spiral striations. Each cell has a single centralchloroplast which is irregular and stellate, withpyrenoids. The central area of the chloroplast has a mass ofparamylon grains, with additional paramylon grains scattered throughout the cell. The single emergent flagellum is roughly as long as the cell , but is sometimes dropped. Cells have a single, reddisheyespot (stigma).[8]
E. viridis typically moves with a squirming motion known asmetaboly; it may also swim very rapidly. The cells can also round up to formcysts.[8]
E. viridis can be distinguished from most otherEuglena species by its one axial, stellate chloroplast with a paramylon center in it. But there are still five species sharing these morphological features.[3]E. viridis differs from similar species (E. stellata,E. pseudostellata, andE. cantabrica) from lacking mucocysts (the mucocysts are only visible after staining with a dye such asneutral red), and is apparently morphologically identical to itssister speciesEuglena pseudoviridis.[6]
Euglena viridis is common in bodies of water rich inorganic compounds.[3] It has acosmopolitan distribution.[2]
Euglena is considered to be one of the most pollution-tolerant algal genera,[9] andE. viridis is anindicator of moderate to heavy pollution.E. viridis commonly forms greenblooms in farmyards and sewage outfalls.[8]
Euglena viridis can be bought as aculture through some institutions[10][11] and can be maintained by replenishing it with freshtap water and fresh leaf blades once a week.[7] Such accessibility lets it easily be used. For example, a research tests new cultivating system by cultivatingEuglena viridis.[7] Additionally,E. viridis is used as teaching material in classrooms in order to demonstrate important biology concepts such as phylogenetic relationships[12] and exponentialpopulation growth.[13]
In awastewaterbiodegradation system, algae can provide theoxygen thatheterotrophicbacteria need for the degradation oforganic matter.[14] The ability to live in polluted water bodies have letEuglena viridis be used as an oxygen producer in wastewater biodegrading systems; it has been proven thatEuglena viridis can enhance biodegradation in piggery wastewater degradation system.[14]
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