BRIEF DESCRIPTION:
This protist that measures from 45 to 65 micras to 14 to 20 micras always has captured my attention. I remember when I received my first microscope as a gift when I was around seven years old. I spent days observing muddy water drops, looking for euglenas (Euglena viridis). In those times, Euglena was classified as a unicellular plant, in the Division Algae. Euglena moves by means of flagella, as if she were a protozoon. Besides, Euglena is a mixotrophic organism (she is a holophytic organism because she produces her own food in chloroplasts, and she is a heterotrophic organism because she absorbs organic matter); besides, Euglena possesses a receptor of light (light sensor) and an eyespot. The complexity of these microorganisms is enough to classify them as a different phylum.
Euglena has an eye-spot for the detection of light. It is situated in the anterior region and it appears as a reddish or brownish dot. Although it cannot be considered to be an eye, it functions as a sensorial organ that perceives the intensity of light. It would determine the direction of Euglena's movements, regularly towards the light source or towards the place where the light is more intense. Euglena's stigma is composed by thirty to fifty granules of beta-carotine.
Euglena excretes by the cytostome and the cytopharinx.
Memo: I am not sure why I am referring to Euglena as a "she", but it sounds well. Anyway, you can also describe her as a "he", or simply as a "tiny green bug".
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