Nematodes are a diverse group of microscopic, non-segmented round worms that are tapered at each end. There are over one million species and they have been estimated to account for 80% of all individual animals in the world. About half of all nematode species are parasites of marine animals (e.g. sperm whales), 25% are free-living non-parasitic soil inhabiting nematodes, 15% are animal and human parasites (e.g. heart worm in dogs) and 10% are plant parasites.