Euglenids
Scientific classification
Domain: Eukaryota (unranked) Excavata Phylum: Euglenozoa Class: Euglenoidea Bütschli 1884
Major groups
Phototrophs    Euglenales    Eutreptiales Osmotrophs    Rhabdomonadales Phagotrophs    ?Heteronematales    ?Sphenomonadales Image File history File links No higher resolution available. ... Scientific classification or biological classification is a method by which biologists group and categorize species of organisms. ... Kingdoms Animalia - Animals Fungi Plantae - Plants Protista Alternative Phylogeny Unikonta    Opisthokonta    Amoebozoa Bikonta    Apusozoa    Cabozoa       Rhizaria       Excavata    Corticata       Archaeplastida       Chromalveolata Animals, plants, fungi, and protists are eukaryotes (IPA: ), organisms with a complex cell or cells, where the genetic material is organized into a membrane-bound nucleus or nuclei. ... This article is about the protist group called excavates. ... Classes Euglenoidea Kinetoplastea Diplonemea Postgaardea The Euglenozoa are a large group of flagellate protozoa, dominated by the euglenids and kinetoplastids. ... Otto Bütschli (1848-1920) was a German zoologist and professor at the University of Heidelberg. ...

The euglenids (also spelled euglenoids) are one of the best-known groups of flagellates, commonly found in freshwater especially when it is rich in organic materials, with a few marine and endosymbiotic members. Many euglenids have chloroplasts and produce energy through photosynthesis, but others feed by phagocytosis or strictly by osmosis. They belong to the phylum Euglenozoa, and their cell structure is typical of that group. Flagellata from Ernst Haeckels Artforms of Nature, 1904 Parasitic excavate (Giardia lamblia) Green alga (Chlamydomonas) Flagellates are cells with one or more whip-like organelles called flagella. ... Chloroplasts are organelles found in plant cells and eukaryotic algae that conduct photosynthesis. ... Phagocytosis (literally cell-eating) is a form of endocytosis wherein large particles are enveloped by the cell membrane of a (usually larger) cell and internalized to form a phagosome, or food vacuole. ... Classes Euglenoidea Kinetoplastea Diplonemea Postgaardea The Euglenozoa are a large group of flagellate protozoa, dominated by the euglenids and kinetoplastids. ...

Euglenids are distinguished mainly by the presence of a pellicle, which is composed of proteinaceous strips underneath the cell membrane, supported by dorsal and ventral microtubules. This varies from rigid to flexible, and gives the cell its shape, often giving it distinctive striations. In many euglenids the strips can slide past one another, causing an inching motion called metaboly. Otherwise they move using the flagella. The pellicle is a thin layer supporting the cell membrane in various protozoa, protecting them and allowing them to retain their shape. ... Microtubules are one of the components of the cytoskeleton. ...

The euglenids were first defined by Otto Bütschli in 1884 as the flagellate order Euglenida. Botanists subsequently treated the algal division Euglenophyta; thus they were classified as both animals and plants, as they share characteristics with both. This conflict is an example of why the kingdom Protista was adopted. However, they retained their double-placement until the flagellates were split up, and both names are still used to refer to the group. Otto Bütschli (1848-1920) was a German zoologist and professor at the University of Heidelberg. ... Typical phyla Chromista Heterokontophyta Haptophyta Cryptophyta (cryptomonads) Alveolata Dinoflagellata Apicomplexa Ciliophora (ciliates) Excavata Euglenozoa Percolozoa Metamonada Rhizaria Radiolaria Foraminifera Cercozoa Archaeplastida (in part) Rhodophyta (red algae) Glaucophyta (basal archaeplastids) Amoebozoa Choanozoa Many others; classification varies Protists (IPA: ) are a diverse group of organisms, comprising those eukaryotes that are not animals...

Classification & Nutrition

The classification of euglenids is still variable, as groups are being revised to conform with their molecular phylogeny. To some extent, however, the results support the traditional groups based on differences in nutrition and number of flagella; at any rate these provide a starting point for considering euglenid diversity. In biology, phylogenetics (Greek: phylon = tribe, race and genetikos = relative to birth, from genesis = birth) is the study of evolutionary relatedness among various groups of organisms (e. ...

As with other Euglenozoa, the primitive mode of nutrition is phagocytosis. Prey such as bacteria and smaller flagellates are ingested through a cytostome, supported by microtubules. These are often Phagocytosis (literally cell-eating) is a form of endocytosis wherein large particles are enveloped by the cell membrane of a (usually larger) cell and internalized to form a phagosome, or food vacuole. ... Phyla/Divisions Actinobacteria Aquificae Bacteroidetes/Chlorobi Chlamydiae/Verrucomicrobia Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Nitrospirae Omnibacteria Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Bacteria (singular, bacterium) are a major group of living organisms. ... A cytostome or cell mouth is a part of a cell specialized for phagocytosis, usually in the form of a microtubule-supported funnel or groove. ...

packed together to form two or more rods, which function in ingestion, and in Entosiphon form an extendable siphon. Most phagotrophic euglenids have two flagella, one leading and one trailing. The latter is used for gliding along the substrate. In some, such as Peranema, the leading flagellum is rigid and beats only at its tip.

Phototrophic euglenids

Chloroplasts presumably originated from some ingested green alga. They are pigmented with chlorophylls a and b, giving them a bright green colour. Often they are associated with granules of paramylon, a storage carbohydrate that is unique to the euglenids. Most coloured euglenids also have a stigma or eyespot, which is a small splotch of red pigment on one side of the flagellar pocket. This shades a collection of light sensitive crystals near the base of the leading flagellum, so the two together act as a sort of directional eye. The cytostome is a vestigial, although nutrients may still be obtained by absorption. Divisions Chlorophyta Charophyta Streptophytina (Subdivision) The green algae are the large group of algae from which the embryophytes (higher plants) emerged. ... Chlorophyll gives leaves their green color Space-filling model of the chlorophyll molecule Chlorophyll is a green photosynthetic pigment found in most plants, algae, and cyanobacteria. ... Paramylon is a carbohydrate similar to starch. ... Lactose is a disaccharide found in milk. ...

A few coloured euglenids have two roughly equal flagella, such as Eutreptia, and some have four. In most, however, the trailing flagellum is shortened so that it does not emerge from the flagellar pocket. The emergent flagellum typically undergoes a complex looping motion that pulls the euglenid along a slightly helical path. These include the common genera Euglena, Phacus, and Trachelomonas, which produces an organic lorica that encases the cell. There is also one genus, Colacium, in which the mature cells are non-motile and form branched colonies supported by mucous stalks. Euglena is a common flagellate protist, typical of the euglenids, and commonly found in nutrient-rich freshwater, with a few marine species. ...

Whereas chloroplasts in green algae and higher plants are surrounded by two membranes, those in euglenids are surrounded by three. The extra membrane presents a barrier to the import of chloroplast precursor proteins not present in the simpler two-membrane chloroplasts, where chloroplast proteins are synthesized on free polysomes and then post-translationally imported directly into the chloroplasts. In euglenids protein import is fundamentally different, with three steps: A biological membrane or biomembrane is an enclosing or separating tissue which acts as a barrier within or around a cell. ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... Polysomes (polyribosomes) are free ribosomes engaged in protein synthesis and may appear as clusters, linear arrays, or rosetts in routine. ... Translation is the second process of protein biosynthesis (part of the overall process of gene expression). ...

1. Synthesis on polysomes bound to the rough endoplasmic reticulum (ER) with co-translocation into the ER;
2. Transport from the ER into the Golgi apparatus; and
3. Import across the three chloroplast membranes.

The extra membrane reflects the secondary origin of euglenid chloroplasts from another eukaryotic algae, rather than from prokaryotes as in plants and other Archaeplastida. A third membrane is also found in the chloroplasts of most dinoflagellates, while many other algae have chloroplasts with four membranes. The endoplasmic reticulum (endoplasmic meaning within the cytoplasm, reticulum meaning little net in Latin) or ER is an organelle found in all eukaryotic cells that is an interconnected network of tubules, vesicles and cisternae that is responsible for several specialized functions: Protein translation, folding, and transport of proteins (e. ... Diagram of the endomembrane system in a typical eukaryote cell Micrograph of Golgi apparatus, visible as a stack of semicircular black rings near the bottom. ... The Archaeplastida are a major line of eukaryotes, comprising the land plants, green and red algae, and a small group called the glaucophytes. ... Classes Dinophyceae Noctiluciphyceae Syndiniophyceae The dinoflagellates are a large group of flagellate protists. ...

Osmotrophic euglenids

In many cases exposure to certain chemicals or prolonged absence of light may kill off the chloroplasts without otherwise harming the organism. There are a number of species where chloroplasts have been lost, formerly treated in separate genera such as Astasia (colourless Euglena) and Hyalophacus (colourless Phacus). Since they lack a developed cytostome, these forms feed exclusively by absorption.

Some primitively colourless euglenids, such as Rhabdomonas and Distigma, are also strict absorption-feeders. On molecular trees these form a monophyletic group, as do the photosynthetic euglenids together with their colourless derivatives. In phylogenetics, a group is monophyletic (Greek: of one stem) if all organisms in that group are known to have developed from a common ancestral form, and all descendants of that form are included in the group. ...

In aquaria

Euglena green algae can create green and opaque water problems in aquariums. Euglena can grow due to high Nitrate, Phosphate levels or direct sunlight. Decreasing phosphate and Nitrate by patial water change and moving the aquarium to shade can help in solving the problem. A seaweed (Laurencia) up close: the branches are multicellular and only about 1 mm thick. ... For other uses, see Aquarium (disambiguation). ... An electrostatic potential map of the nitrate ion. ... Above is a ball-and-stick model of the inorganic hydrogenphosphate anion (HPO42−). Colour coding: P (orange); O (red); H (white). ...

External links

• The Euglenoid Project