Gyrodactylus turnbulli is an ectoparasite from the class Monogenea, is part of the phylum Platyhelminthes, and from the genus Gyrodactylus. It only requires one host to transmit an infection; however, since this parasite lacks oncomiracidium, it must rely on either the adult or subadult for spread of infection (Roberts and Schmidt, 2009). Found in freshwater, this flatworm is commonly found on the gills and fins of the guppy, Poecilia reticulata. G. turnbulli was said to be host specific, but an experiment where parasitologists artificially infected guppies suggests that the parasite can infect a wider range of species. This ability is achievable by host switching, which promotes speciation.