Nematode worms. Coloured differential interference contrast (DIC) light microscopy footage of specimens of the nematode roundworm Caenorhabditis elegans. Nematodes are small worms found in a range of environments worldwide. C. elegans is a transparent, soil-dwelling nematode, found in temperate climates. It feeds on bacteria, and reaches lengths of about 1 millimetre. C. elegans is used extensively in biological research. It can reproduce by self-fertilisation (resulting in identical offspring), and takes a short time to reach maturity.