Nematodes are the most diverse phylum because they consist of 1 million various species. Much like the Porifera and Platyhelminthe phylums the Nematodes respiratory system is through oxygen diffusion.
Trichuris trichiura
A worm that causes trichuriasis when it infects a human large intestine. It is commonly known as the whipworm which refers to the shape of the worm. It looks like a whip with wider "handles" at the posterior end. Infection occurs commonly through eggs in warm areas.
Dirofilaria immitis
Also known as a heartworm, this nematode is a parasitic roundworm that spreads from host to host through the bites of mosquitoes. The primary effect on the health of the animal is damage to the lung vessels and tissues. Occasionally, adult heartworms migrate to the right heart and even the great veins in heavy infections.
Myrmeconema neotropicum
A tetradonematid nematode parasite that induces fruit mimicry in the tropical ant Cephalotes atratus. Infected ants develop bright red gasters, tend to be more sluggish, and walk with their gasters in a conspicuous elevated position. These changes likely cause frugivorous birds to confuse the infected ants for berries and eat them. Parasite eggs passed in the bird's feces are subsequently collected by foraging Cephalotes atratus and are fed to their larvae, thus completing the life cycle of Myrmeconema neotropicum.