Tylodelphys

Tylodelphys is a genus of parasitic fluke that infects the small water fish. It induces many behavioral changes on its host. Once inside a fish's eye, it can cause partial blindness and several behavioral changes to the intermediate host. Other species of flukes are able to turn into dormant cysts at certain stages of development, but Tylodelphys spp. stays active and roams free inside the fish's eye, giving it an opportunity for it to induce parasite behavior. When Tylodelphys larvae crawl around the inside of the fish's eye, it can get in between the retina and the lens. This can cause partial blindness to the fish, rendering the fish unable to notice predators. Tylodelphys consists of two species, Tylodelphys clavata (von Nordmann, 1832) and Tylodelphys podicipina Kozicka & Niewiadomska, 1960.

==Life cycle== Tylodelphys spp. has a complex three-host life cycle, with a variety of fish- and amphibian-eating birds and lymnaeid or planorbid gastropods as first intermediate hosts. Tylodelphys must enter the gut of fish-eating bird, which would naturally involve the fish being eaten by the said bird such as ciconiiforms, suliforms, falconiforms and podicipediforms acting as definitive hosts. Tylodelphys species can also infect the brain or the body cavity of their second intermediate hosts, which are typically fish but sometimes amphibians. The common intermediate host, the bully, Tylodelphys dwells in its host's eyes in the vitreous liquid between the lens and the retina.