Nematodes move through the contraction of their longitudinal muscles. There is high internal body pressure when these muscles contract, which causes the body of the nematode to flex instead of flatten. The thrashing caused by this back and forth movement propels a nematode forward.
Nematodes have no cilia or flagellae to help with their movement, according to the University of Michigan Museum of Zoology.
During the fertilization process, a male nematode uses copulative spines to open the female's reproductive tracts to inject sperm into them. Nematode sperm also doesn't have any flagellae present and therefore, they move using pseudopodia in the same way as amoebas. Nematodes, or round worms as they are commonly called, are simple worm-like organisms that are highly abundant in the environment. There are over 12,000 described distinct species of nematodes with some types occurring widely in many different environments, while others are specialized to one particular habitat.
The nematodes play a critical role as decomposers and predators of many microorganisms in the environmental ecosystem. However, nematodes can also infect humans both directly or indirectly through contact with domestic animals. Common species that infect humans include pinworms, hookworms and trichina, which is the parasite that causes trichinosis.