I observed my microaquarium on Thursday, November 8th and again on Friday, November 9th. The microaquarium was full of active life from the top to the bottom of the water column. Near the surface of the water were dozens of halteria (figure 1) which were moving around constantly at a slow pace punctuated by a sudden jump every thirty seconds or so. Ken Mcfarland explained to me that the haltaria have a vacuole that allows water to diffuse into the organism which it must then discharge, causing the sudden jump in location, (Patterson, p.139, fig. 305).
Figure 1(Patterson, 1996: p.139)
I observed one large nematode that was feeding on a dead copopod which was a fascinating process to watch. There were a few, maybe five or ten, euplotes (figure 2) that were actively seeking food and moving rapidly throughout the water column. They did not seem to be restricted to any particular area of the microaquarium, though they seemed to prefer the middle third of the aquarium. A few of the euplotes were moving much quicker than the others, and their movement was in a spiral corkscrew pattern causing the euplote to fade in and out of focus when looking through the microscope, (Patterson p.124, fig.259).
Figure 2 (Patterson, 1996: p.124)
There were a few scattered diatom stacks, identified by Ken Mcfarland, surrounding the ulticularia gibba plant leaves. They were stationary, but still beautiful to observe.
Perhaps the most interesting organism I observed near the top of the water column were two Rotifers philodina (Rainis, p. 188, fig. 88). Their feeding mechanism was so bizarre to observe as they use an 'egg-beater' style motion to suck their food source into their mouth and they move around like a telescope would.
Another stationary organism that I found to be quite beautiful were the Ciliophora vorticella (figure 3) that were anchored onto the ulticularia gibba leaves. I only observed about 3 or 4 of them in the entire aquarium, (Rainis p.104, fig. 40).
Figure 3 (Rainis, 1996: p.104)
The organism that I probably observed for the longest amount of time was the only copopod that I saw alive in the entire aquarium. It was very large, barely visible to the naked eye, and moving around in very quick jerky motions. Being such a large organism it was fascinating to be able to see the inner workings of the crustacean's body while chasing it around the aquarium with my microscope.
The middle third of the aquarium was dominated by euplotes all scavenging for food intensely. While the bottom third had more halteria and anisonima (figure 4). The anisonima were interesting because they have two flagella; one to anchor the organism and the other to explore its surroundings with, (Patterson, p.54, fig.77).
Figure 4 (Patterson, 1996: p. 54)
Near the bottom of the tank I observed 2 very slow moving amoeba which appeared to be flowing like a waterdrop, similar to a slug-like movement. I also discovered two gastrotrichs slowly patrolling the waters in random directions possibly scanning for food. Both of these organisms were identified for my by Ken McFarland.
At the very bottom of the tank, there were a few discernible dead organisms, but mostly just a brown collection of sediments and decomposed matter. One organism that I could identify was a dead Ciliophora blepharisma (Rainis p.87, fig. 23). There was another organism that I was very interested in, but unable to identify. It looked similar to a caterpillar, but it was hiding inside one of the ulticularia gibba leaves, making it too hidden to identify. Hopefully next week this organism will emerge in a more accessible location, so I can have a chance to identify it. There were a few euplotes roaming the bottom of the tank, but much fewer than in the middle of the aquarium. Another unique organism Ken McFarland identified was a single euglenid that was mostly inactive and moving extremely slowly if at all. I began to wonder if the organism was perhaps dying.
Overall it was an interesting observation experience, and I look forward to monitoring the progress of this microecosystem in the following weeks.
Bibliography
Patterson, D.J. 1996: Free Living Freshwater Protozoa: A Colour Guide. Washington D.C.: Manson Publishing
Rainis, K.G. 1996 Guide to microlife: Danbury, Connecticut: Grolier Publishing
