Week 3

When viewing my microaquarium this week it was about two-thirds full with water, there was little activity and I found no new forms of life. I then filled the aquarium to the top and organisms then became more visible.

I discovered a thin, unsegmented annelid trapped among a plant stem and several surrounding algae and other material. It was flexible throughout its entire body and its movement was quick in bursts. It viciously flailed and struggled to break free, but it had already escaped before I could identify it. No camera equipment was available at the time. Later, while viewing the aquarium under a microscope with an attached camera, I found another specimen in a similar scenario:
One other annelid was discovered and at first I had supposed it was an organism under the order Tricladida (Pennak 1989). No kind of gut or any other distinctive features were visible except for the location of its eyes. This made identification dificult and I began questioning my initial guess and with help from Dr. McFarland I had also considered it as Stenostomum.


The debris at the bottom of the aquarium had dimished since I last observed it, and many organisms in this area seemed to no longer be present, or had a lower than previous presence. This includes Cyclops, Perididium, and Actinosphaeria.
However, diatoms Pinnularia and Rhopalodia gibba had greatly increased in number in the bottom third.
Other organisms that have increased in number throughout the entire aquarium include Succamoeba lucens and Vorticella.

Citations

Pennak, R. W. (1989). Fresh-Water Invertebrates of the United States. 3rd Ed. United States: John Wiley & Sons, Inc. p140. 620 pgs.