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Euglena is a genus of single cell flagellate eukaryotes. It is the best known and most widely studied member of the class Euglenoidea, a diverse group containing some 54 genera and at least 200 species. [1] [2] Species of Euglena are found in fresh water and salt water.
Two genera, Strombomonas and Trachelomonas produce outer shells called loricae. [ 4 ] As with other euglenids, cells in the Euglenaceae are surrounded by a series of proteinaceous strips called the pellicle ; the pellicle can stretch in most genera, allowing the cell to contract, creating a type of movement called metaboly.
Within its taxon, the pellicle is one of the euglenoids' most diverse morphological features. [7] The pellicle 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.
Euglenales consists mostly of freshwater organisms, in contrast to its sister Eutreptiales which is generally marine. Cells have two flagella, but only one is emergent; the other is very short and does not emerge from the cell, so cells appear to have only one flagellum. [3]
Euglenophyceae encompasses three taxonomic groups: the mixotrophic Rapaza viridis and two mainly phototrophic orders, Euglenales and Eutreptiales. [1] [3] [6] The classification is as follows (species numbers based on AlgaeBase): [7] Order Euglenales Leedale, 1967 emend. Marin & Melkonian, 2003. Family Euglenaceae [Euglenidae] Dujardin, 1841 ...
The red eyespot of a euglena filters light for the photoreceptor so that only certain wavelengths of light are able to reach the photoreceptor, allowing the euglena to “steer” itself by moving toward light in different intensities in different areas of its photoreceptor. Key: 1. Microtubules that make up the pellicle (see 9.) 2.
Schematic representation of a Euglena cell with red eyespot (9) Schematic representation of a Chlamydomonas cell with chloroplast eyespot (4). The eyespot apparatus (or stigma) is a photoreceptive organelle found in the flagellate or (motile) cells of green algae and other unicellular photosynthetic organisms such as euglenids.
This is supported by one of three sets of microtubules that arise from the flagellar bases; the other two support the dorsal and ventral surfaces of the cell. [ 4 ] Some other euglenozoa feed through absorption, and many euglenids possess chloroplasts , the only eukaryotes outside Diaphoretickes to do so without performing kleptoplasty , [ 5 ...