|MadSci Network: Cell Biology|
Hello Lindsey! Euglena, Paremecium, and amoebae are all examples of single-celled protists. The protists are an extremely diverse group of mostly small unicellular organisms, although the large seaweeds and kelps are also protists. Euglena is a single-celled green alga. It has chloroplasts, and thus a green color. Euglena also has a reddish eyespot, which it uses to detect the appropriate light intensity to enhance photosynthesis. However, Euglena is not solely autotrophic - under low light conditions, it can live as a heterotroph, absorbing dissolved organic matter (DOM) from the environment. In fact, there are some close relatives of Euglena that lack chloroplasts and thus are not photosynthetic. But Euglena itself is green. Here's a link to a video of a single Euglena cell smooshing around under a microscope; you can see the green chloroplasts and the red eyespot: http:// micro.magnet.fsu.edu/moviegallery/pondscum/protozoa/euglena/rostrifera/56k/ rostrifera02.html The amoebae are themselves a very diverse group of unicells. There are many kinds of amoebae, but they all use pseudopodia ("false feet") to move over surfaces. The standard naked amoeba, which you might have seen in the laboratory, is a fairly colorless cell. Under phase-contrast light microscopy, it might be a pale bluish-gray color, but they don't have much pigmentation. This link will take you to a video of an amoeba engulfing a food particle: http://micro.magnet.fsu.edu/moviegallery/pondscum/protozoa/ amoeba/56k/amoeba05.html Some amoebae have shells or skeletons. The foraminiferans (forams) have a calcium carbonate shell that resembles a snail's shell. The shell is opaque and whitish, although the cell itself is colorless. Radiolarians and acantharians have beautiful skeletons of transparent glass-like rods. Again, the cell and the skeleton are mostly colorless. Here's a photo of radiolarian skeletons: http://micro.magnet.fsu.edu/primer/techniques/ phasegallery/radiolarians.html Paramecium is a ciliate. It is non-photosynthetic, and thus has no chloroplasts. Paramecium cells are mostly colorless, and in terms of color resemble amoeba cells. You can see for yourself: http:// micro.magnet.fsu.edu/moviegallery/pondscum/protozoa/paramecium/t1/ paramecium04.html Allison J. Gong Mad Scientist
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