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Like other euglenoids, Euglena possess a red eyespot, an organelle composed of carotenoid pigment granules. The red spot itself is not thought to be photosensitive . Rather, it filters the sunlight that falls on a light-detecting structure at the base of the flagellum (a swelling, known as the paraflagellar body), allowing only certain ...
Euglena gracilis is a freshwater species of single-celled alga in the genus Euglena. It has secondary chloroplasts , and is a mixotroph able to feed by photosynthesis or phagocytosis . It has a highly flexible cell surface, allowing it to change shape from a thin cell up to 100 μm long to a sphere of approximately 20 μm.
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.
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]
Euglenaceae show the most morphological diversity within the class Euglenophyceae. [3] They are mostly single-celled organisms, except for the genus Colacium.They are free-living or sometimes inhabiting the digestive tracts of animals. [1]
Euglena viridis is a freshwater, single cell, mixotroph microalgae bearing a secondary chloroplast. [1] Their chloroplast is bounded by three layers of membrane without a nucleomorph . [ 2 ] Normally, it is 40–65 μm long, slightly bigger than other well-known Euglena species: Euglena gracilis .
Later, various biologists described additional characteristics for Euglena and established different classification systems for euglenids based on nutrition modes, the presence and number of flagella, and the degree of metaboly.
The fossil record for Phacus, like most euglenoids, is very scarce, and little information is actually known of their geographical origins. However, there have been reports that Phacus-like microfossils have been discovered from pyriform cells, which seem to closely resemble that of Phacus or another closely related genus, Lepocinclis. These ...