#669: Roundworm

There are perhaps as many as 1 million species of Roundworm, a Phylum of Nematode, over half of which are parasitic. Widespread and versatile, various species inhabit every ecosystem from the deepest oceanic trenches to the driest deserts. They are also, most famously, known to occupy the internal organs of vertebrates, but species are also adapted to parasitise plants and insects as well. Long and slender, parasitic Roundworms have a distinctive head, which may contain head shields and three or six lips, equipped with an array of teeth. They may also be ornamented with bristles, ridges and other distinctive structures. Eggs are deposited in the soil via the host's fecal matter, where they can be ingested directly, or indirectly, by a new host. Once hatched, the larvae may affect the host's behavioural patterns and can have a detrimental effect on their health.