As my last observation, I would like to spend some time discussing several organisms that have been present and multiplied throughout the duration of this term project. These include: the rotifer, the peritrichs, and the ostracod. (photos were taken by me)
Firstly, the Rotifers:
Rotifers are part of the Phylum Rotifera. The name is derived from Latin, meaning "wheel-bearer", which most likely refers to the rapid movement of the cilia around the mouth. They use these long, coronal cilia to catch food by creating a vortex which draws water and food particles into the rotifers complete digestive track. These multicellular, microscopic animals are found in either still or flowing freshwater, and prefer mosses and lichens as anchoring ports. Their mostly soft bodies are composed of four basic regions: corona (crown), trophi (jaws), pharynx (throat), and foot (attachment feature). Because of their small size, they are often found as fossils. The oldest reported fossil was found in Dominican amber.
Secondly, Peritrichs:
Peritrichs are Protozoa in the Ciliates group. They frequently exist as separate, stalked organisms or branched colonies. These stalks attach to any submerged plant material and use cilia around the mouth of the peritrich to create a food-bringing current. The classic organism is called the Vorticella which means "bell animalcule", referring to the shape it takes when fully extended. Found in freshwater, they eat mostly bacteria, algal unicells, and smaller protozoa. The stalk is contractile and can pull into a tight spiral if the organism is disturbed. This contracile action holds the record for the fastest action in the animal kingdom! If ever the peritrich needs to find a new, more favorable enviornment it can detatch itself and swim freely elsewhere. In this state it is referred to as a telotrach.
Lastly, Ostracod:
Ostracods are crustaceans. Found in both fresh and marine water, ostracods are distantly related to the shrimp family. This similarity is more easily seen in the marine variety because of their larger size. The freshwater, like the ones in my aquarium are much much smaller. As observed, they tend to spend most of their time and energy along the edges, submerged in the debris and muck of the lower levels...not swimming freely in open water. Appendages extend from between the two halves of their carapace shell. This shell is somewhat patterned and not transparent, making it hard to see the internal structure of the ostracod. However, it is obvious that their level of activity is very high, as they are so hard to keep in your microscopes eye. their activity is ceaseless. If disturbed, they will clamp the two halves together for protection. I also observed the remaing exoskeletons left over from a moulting or from a dead ostracod whose internal remains have been eaten. Ghostly and transparent, these skeletal remains are only a vague memory of their former selves.
That's all folks!
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