Euglena

Euglena
	;
Scientific classification
Domain:	Eukaryota;
Kingdom:	Excavata;
Phylum:	Euglenophyta;
Class:	Euglenoidea;
Order:	Euglenales;
Family:	Euglenaceae;
Genus:	Euglena; Ehrenberg, 1830

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Euglena is a genus of unicellular protists, of the class Euglenoidea of the phylum Euglenophyta. They are single-celled organisms. Currently, over 1000 species of Euglena have been described. Marin et al. (2003) revised the genus to include several species without chloroplasts, formerly classified as Astasia and Khawkinea. Euglena sometimes can be considered to have both plant and animal features.

A euglena is a protist that can eat food like animals do (partly heterotrophic) and can photosynthesize like plants do (partly autotrophic). Euglena can surround a particle of food and eat it (phagocytosis). Many Euglena use a light-sensitive ocular receptor to detect and hunt other protists. Many Euglena also have chloroplasts, which contain chlorophyll a, chlorophyll b, and some carotenoid pigments. Euglena live in fresh water, salt water and in marine-like environments. Many Euglena are able to move by using a flagellum, a long whip-like structure. When the water dries up, a euglena forms a protective wall around itself and lies dormant in the form of a spore until the environment improves. It reproduces by mitosis, splitting into parts, like amoeba.

Euglenas have three distinctive methods of nutrition. They are the holozic, saprophytic, and holophytic methods. Euglenas use the holozic method meaning they ingest solid particles of food. They feed by absorbing dissolved substances through their body wall, which is the saprophytic method of nutrition and plays an important role in the free active swimming phase of the Euglena. They can be classified as animals because they can swim actively and some can ingest larger materials such as other euglenoids. The holophytic method predominates in the encysted forms. It means they obtain nourishment as green plants do by utilizing simple chemical elements like water and carbon dioxide as food for metabolism. Euglenas reproduce asexually by fission, and there has been no existence of sexual reproduction. Reproduction includes transverse division and longitudinal division, which both occur in the active and encysted forms. Acidity and alkalinity are both important factors to consider in Euglenas because they help control reproduction, life spans and nutrition.

Euglena lack cell walls but have pellicle instead. Pellicle is made of protein bands that spiral down the length of the Euglena and lie beneath the plasma membrane. The pellicle provides strength and flexibility to Euglena. The pellicle complex of Euglena is composed of the cell membrane, the ridge and groove with the notch, four fibrils, and a subpellicular ER.

Euglena are monophyletic and contain chloroplasts. The chloroplast and plastid of Euglena have arisen by secondarily through an endosymbiotic event with eukaryotic green alga. Chloroplasts of Euglena are surrounded by three membranes and exist in thylakoid stacks of three. The number and shape of chloroplasts within Euglena varies greatly due to environmental conditions and evolutionary history. Some descendents have lost photosynthesis altogether, while others bleach chloroplasts. This bleaching effect occurs when Euglena survive in the dark. Euglena store paramylon granules in pyernoids within the chloroplast. Paramylon granules are beta-1,3 glucan storage carbohydrate. Mature paramylon granules are highly crystalline, fibrillar, and have a complex substructure.

The eyespot is an organelle that shields the light detector from light, allowing only a certain wave of light to hit it. The eyespot acts as shade for the light detector and regulates the amount of light that strikes it. The light detector is located at the base of the flagellum and detects light that is not blocked by the eyespot. When such light is detected, the Euglena moves toward the appropriate intensity, enhancing photosynthesis. Because of this adaptation, many Euglena are mixotrophs; they are autotrophs in sunlight and heterotrophs in the dark.

Euglena live in a marine and fresh water habitat. Their flagellated tail allows them to be mobile. Euglena can move to different environments with the aid of birds and other animals by attaching to them by wet mud. Since euglena feed on algae, the presence of them in pools can be a good indicator of contamination and lack of chlorine.

There are many possible uses of Euglena being researched. Euglena is rich in nutrients and contains paramylon. Currently there is one Euglena product already in the market called Biozyme Euglena. Biozyme Euglena is developed and produced by a Japanese company called Euglena Co. Ltd. with the help of the University of Tokyo. Biozyme Euglena contains Euglena, royal jelly, condroitin, and brewers yeast. The product is suppose to be a dietary supplement, good antioxidant, and colon cleanser. The same company is looking into other possible uses of Euglena like the application of paramylon. The possible applications of paramylon include use in cosmetics, biodegradable film, and drugs.

[edit] References

"Phylogeny and taxonomic revision of plasmid-containing neophytes based on USU DNA sequence comparisons and signatures in the USU RNA secondary structure."

Berlin, Springer. 2005. Nutrition and reproduction in euglena. Biomedical and Life Sciences. 52: 367-383.

Campbell and Reece. (2008) Biology (Ed. 8, pp. 580-581).

Campbell, Neil A. and Reece, Jane B. 2008. Biology Eighth Edition. Pearson Benjamin-Cummings. San Francisco, CA.

Kiss, J.Z., E. M. Roberts, R. M. Brown Jr. and R. E. Triemer. 1988. X-ray and dissolution studies of paramylon storage granules from Euglena. Protoplasma. 146: 150-156.

Kusel-Fetzmann, lsa and Weidinge, Marieluise. 2008. Ultrastructure of five Euglena species positioned in the subdivision Serpentes. Protoplasma. 233: 209-222.

Sommer, Joanchim R. 1965. The Ultrastructure of the Pellicle Complex of Euglena Gracilis. The Journal of Cell Biology. 24: 253-257.

Vliet, Kent A. 2008. A Lab Manual for Integrated Principles of Biology Part one- BSC2010L Forth Edition. Pearson Custom. University of Florida.