The image shows the head of Dorylaimus sp., an omnivorous nematode which is able to feed on different food sources depending on the environmental conditions and food availability. Dorylaimus has a big hollow tooth that can be used as a stylet to puncture other organisms or to suck liquids. The nematodes can function as predators, feeding on protozoa and possibly other nematodes when available, but changing to feeding on fungi and bacteria when its primary food source is no longer available. Feeding habits may also change from juvenile to the adult stage, for instance from bacterial feeding in the juvenile stage to becoming predatory in the adult stage.
(Source: European Atlas of Soil Biodiversity|Section2: Organisms of the Soil)