Protozoa (Kingdom) : Eozoa (Subkingdom) : Euglenozoa (Infrakingdom) : Euglenozoa (Phylum) : Euglenoidea (Class) : Euglenia (Subclass) : Euglenida (Order) : Euglenaceae (Family) : Euglena (Genus) 
Description and Significance
This algae is found in fresh water environments all over the planet. Like many other members of the algae(Protists subgroup) its seems to be capable of both sexual and asexual reproduction.   It is also relies on chlorophyll for photosynthesis as well as accessory pigments. It produces an interesting compound toxic to many fish species, and can also overgrow under certain conditions also leading to fish death.  Understanding this microorganism is very important to fishing and fish-farming industries because under certain conditions this algae can have a detrimental impact on its surroundings. 
Structure, Metabolism, and Life Cycle
E. sanguinea is generally cylindrical with a blunt pointed end. They are capable of altering their shape, especially during motility: for example, they can extend their length up to ten times their width. They have a retractable flagellum, that remains mostly within the cell body, even when it is fully extended. They have also be noted to have granular eye spots of many varieties. They have been shown to reproduce asexually by mitosis.  There is some evidence indicating meiosis in E. sanguinea and other Euglenineae.  
The algae is photosynthetic (autotroph) containing chlorophyll and an accessory pigment, astaxanthin(a carotenoid). The accessory pigment prevents the cell's chloroplast from being overwhelmed by under excessively bright conditions. The cells will appear red when utulizing this accessory pigment, and green when these pigments are retracted into vesicles. 
This algae produces a compound known as euglenophycin. "The compound exhibits ichthyotoxic, herbicidal and anticancer activity at low ppm to ppb dosages."  Note: Ichthyotoxic means toxic to fish.
Ecology and Pathogenesis
This protist is found in freshwater environments all over the world. They are a major source of food and oxygen in their habitats.
They produce a compound that is toxic to many freshwater fish at high concentrations. "Fish tested with cultured E. sanguinea cells and with filtrate from the cultures exhibited disorientation during exposure, with accelerated respiration and an inability to maintain equilibria. Gill tissue was reddened, however no distinct haemorrhaging was evident. No other distinct histopathology was seen. We suggest that the toxin functions as a neurotoxin based upon the behavioural changes. Juvenile catfish exposed to cultures of the algal isolates died within 2 h of exposure." 
 WoRMS (2011). "Euglena sanguinea Ehrenberg, 1830". In M. D. Guiry & G. M. Guiry. AlgaeBase. National University of Ireland, Galway. World Register of Marine Species. http://www.marinespecies.org/aphia.php?p=taxdetails&id=163127.
 Paul V. Zimba, Peter D. Moeller, Kevin Beauchesne, Hannah E. Lane, Richard E. Triemer. Identification of euglenophycin – A toxin found in certain euglenoids. Toxicon, Volume 55, Issue 1, January 2010, Pages 100–104 http://dx.doi.org/10.1016/j.toxicon.2009.07.004
 P.V. Zimba, M. Rowan, R. Triemer. Identification of euglenoid algae that produce ichthyotoxin(s). Journal of Fish Diseases, 27 (2004), pp. 115–117
 "Euglena Sanguinea — Details." Encyclopedia of Life. N.p., n.d. Web. 20 July 2013.
 The Cell Morphology and Division of Euglena deses Ehrbg. Mary Gojdics. Transactions of the American Microscopical Society , Vol. 53, No. 4 (Oct., 1934), pp. 299-310. Published by: Wiley on behalf of American Microscopical Society. Article Stable URL: http://www.jstor.org/stable/3222381
 HAAS~, G. : Studien fiber Euglena sanguinea. Arch. Protistenk. g0, 47--59 (1910).
 Leedale, Gordon F. "The Evidence for a Meiotic Process in the Euglenineae - Springer." The Evidence for a Meiotic Process in the Euglenineae - Springer. From the Department of Botany, University of Leeds, England, 05 Apr. 1962. Web. 21 July 2013.
Page authored by Romi Salti, student of Mandy Brosnahan, Instructor at the University of Minnesota-Twin Cities, MICB 3301/3303: Biology of Microorganisms.