The pattern of locomotion is remarkably varied amongst the nematodes. Common forms of locomotion include sinusoidal progression, springing from a tightly coiled body, spiralling through a medium by pushing laterally and generating force anteriorly, annelid type extension and contraction or even looping like a leech. Feeding Food material is drawn into the mouth by the actions of a powerful pumping pharynx, before being forced down the digestive tract by contraction and relaxation of the body musculature. The feeding habits and oral apparatus of the nematodes are notably diverse. Many round worms are saprotrophic and actively break down organic material, such as leaf-litter.
Predatory forms are also common, and feed upon other small animals or even other nematodes.
Free living and parasitic nematodes of animals and plants are widespread throughout the globe. Predatory forms often have specialised teeth that line the buccal cavity. Species that parasitise plants commonly have a modified oral spine, or stylet , which can be used to penetrate, and possibly suck, fluids from its host. The nematodes are also a never-ending supply of food for other predatory animals and even some fungi, which lasso the nematodes with specialised hyphal structures. Reproduction and Development Most nematode species are dioecious and exhibit some degree of sexual dimorphism, with females typically larger than their male counterpart.