Identifying the movements

On Thursday, October 23rd, I had the opportunity to view my micro-aquarium through a microscope equipped with a camera. There were a couple of different organisms that I focused on throughout the span of time allotted for viewing. One turned out to be some type of rotifer, but still has not been 100% identified so I will concentrate on describing, in more detail, the organism that was dragging his home with him last week. With the help of the book, Fresh Water Invertebrates of the United States, by Robert Pennak, on page 301, figure 11,example (f), and the shape of the posterior, I was able to identify this amazing creature (Pennak 1989). He is a Dero Furcatus sp.
When I initially began to scan the aquarium for him, I could not find him. When I had left him the week before, there was no denying where he was because he was so large, and so active, but while searching initially this week, nothing. While scanning I finally came across a branch that looked like what I had viewed the week prior and followed it out to the end expecting tho see the head that I had seen with a suction cup mouth, but instead I saw what seemed to be antennae. As I continued to view this guy, it became quite apparent that this was not the head. The length of the body is totally transparent so movement through the body can easily be observed. Excrement release became the clue I needed to look elsewhere for the head. After the dero had completed his private affair, he became as active as he had been the week before. Later on in my study of the dero, he became very still once again, so I decided to immediately examine the posterior side of the dero to see if there was any correlation between it being still and excreting waste. Sure enough, that is what was going on. He would stretch out straight to allow his body to work the waste down his tube body until it was exited. After the waste was excreted, he began to again move constantly looking for his next meal. One more thing that I observed, that I wanted to be sure to make mention of in this post is the fact that I have not seen the dero leave this home that he has carved out of the plant stem. I have observed him, on several occasions, become entangled in other vegetation. When this happens, he simply runs his head down the length of the stem, and pulls his tail through to the other end and goes on his merry way. (The head and tail together on one end of the stem can be seen in the top image below as he is making his rerouting transition.)

                               

Top: Dero turning around with anterior and posterior regions visible              Bottom: Posterior region used for identification             

Bibliography:

      Pennak, Robert W. Fresh-water Invertebrates of the United States. 3rd ed. New York: John Wiley & Sons, 1989.cited October 25, 2014. Print.