Observation #3

Observation

      Last week, after the food pellet was added, I observed rapid growth of the population in my aquarium. Many more organisms were present, resulting in higher competition, which has led to many more dead organisms in the tank this week.

      I've identified my clear, long, worm-like creatures as Nematodes. I haven't seen the carpenter's ruler colonies in the past 2 weeks, but many more diatoms altogether. I observed small ellipsoid-shaped diatoms stuck to some root-like plant structures, as well as more of the square diatoms I described last week. My water sample is full of cyanobacteria colonies, I was unable to identify these until this week, but the species looks like Oscillatoria; hairlike structures that twitch and move slowly and smoothly. I took a video of a Lacrymaria sp. near the bottom of my aquarium, identified from the book Free-Living Freshwater Protozoa, D.J Patterson, 1996, p. 138, figure 301.

      The Lacrymaria is the amorphous organism I described last week, one can see from the video how it moves. The contracting and expanding of the vacuole in its posterior makes the organism able to extend its "neck" and "tail".

I find the mechanism of motion very interesting, but also slightly repulsive. But Dr. McFarland eased my nausea by informing me that there are unicellular organisms like this inside my own body...