ROUND WORMS
Nematodes are the most numerous multicellular animals on earth. A handful of soil will contain thousands of these microscopic worms, many of them parasites. Free-living species are abundant, including nematodes that feed on bacteria, fungi, and other nematodes. There are nearly 20,000 described species classified in the phylum Nemata. Nematodes are structurally simple organisms. Adult nematodes are comprised of approximately 1,000 somatic cells, and potentially hundreds of cells associated with the reproductive system. Nematodes have been characterized as a tube within a tube; referring to the alimentary canal which extends from the mouth on the anterior end, to the anus located near the tail. Nematodes possess digestive, nervous, excretory, and reproductive systems, but lack a discrete circulatory or respiratory system. In size they range from 0.3 mm to over 8 meters.
| Development: Protostomous |
| Body cavity (between endo- and ectoderm): Pseudocoelom |
| Digestive System: Complete |
| Circulatory System: Absent |
| Excretory System: Renette cells or their derivatives |
| Nervous System: Longitudinal nerves and a nerve ring around the pharynx |
| Reproductive system: Separate sexes |
| Claim to Fame: Roundworms have been claimed to be the most numerous and ubiquitous type if animal on the Earth; extraordinarily successful, they and their eggs are found virtually everywhere |
Melodoigyne incognita
Diagram of a Nematode
