(a) Nematode
The nematode was a member of my aquarium, this nematode spend most of its time around the bottom part of the aquarium, close to the soil but during my observation I noticed the nematode swimming around the middle of the aquarium. Nematode worms have round elongate bodies that usually taper nearly to a point at both ends. Unlike flatworms, they have no cilia. The body is enclosed in a tough cuticle. Just under the epidermal layer of the body wall are bundles of longitudinal muscles; there are no circular muscles. The lack of circular muscle and the stiff cuticle severely limit the types of movements possible for the worms, and they usually thrash about in what appears to be a random and inefficient manner (keeton).
Nematodes are extremely abundant, and occur in almost every type of habitat. Of the many free-living in soil or water, most are very tiny, often microscopic. A single spadeful of garden soil may contain a million or more, and a bucket of water from a pond usually contains comparable numbers. many of the nematodes are internal parasites on both plants and animals; these also are often small, but some may attain a length of 3 feet or more (Keeton).
Citation:
Keeton, W. Biological Science pg 176
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