Notable Changes this week:
Water had evaporated substantially, leaving about ony 25-30% of original moisture. Added fresh water from lab source (distilled?) as a refill. Noted several green organisms not noticed before. One is a Desmid, about 12 of these near center of tank, slowly moving, more like floating. These are identified under 40x microscoope, look like European cucumbers, and are apparently single celled because of the single nucleus at the restrictum. Also noted 3 or 4 Pleurotonea, also green, stick-shaped, also single cell with a distinct dividing line in the center.
Also, one prevously unnoticed animal, possible the Cyclops from last week in another life phase. Also, what were previouslt thought to be paramecia are more likely Spirostome, pictured and described below. Information from: http://www.microscopy-uk.org.uk/index.html?http://www.microscopy-uk.org.uk/pond/index.html
The genus Spirostomum contains some of the largest Ciliates. The species pictured on this page, Spirostomum ambiguum, can grow to to a size of more than 4 millimetres. It can therefore be seen without the help of a microscope. When observed swimming in a little jar of pond water it looks like a little worm. Only with the help of a microscope you can see that it is a ciliate. The cell of this unicellular is totally covered with hairlike 'cilia'. On the picture you can see the rows of cilia running like a spiral along the body.
One of the remarkable things of Spirostomum is the way it can contract. The organism can contract it's body to 1/4 of it's length in 6-8 millisec which is the fastest contraction known in any living cell. When observing the creature under the microscope it is easy to watch the contraction by gently touching the sample.
One of the remarkable things of Spirostomum is the way it can contract. The organism can contract it's body to 1/4 of it's length in 6-8 millisec which is the fastest contraction known in any living cell. When observing the creature under the microscope it is easy to watch the contraction by gently touching the sample.
Like many large single celled organisms (giant amoebas, or Stentor: the trumpet animalcule) it has not one nucleus but many. The nucleii form a long strand, like a string of pearls, visible as the lighter structure in the right image.
Spirostomum, like many cilates, feeds on bacteria. They are swept into the mouth opening with a row of specialized fused cilia. The mouth opening is very small and can be found on the side of the body.
These critters move in a spiral, slow fashion.
A variety of Desmids are shown below. The cucumber shaped one ant the more stick-shaped Pleurotoneum are in the study tank. Photo from
DESMIDS
by Wim van Egmond
http://www.microscopy-uk.org.uk/index.html?http://www.microscopy-uk.org.uk/pond/index.html
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