👉 Nematoproctus is a type of protozoan parasite that lives in the gut of certain species of fish, primarily in the stomach and intestines. It is commonly found in freshwater environments such as lakes, rivers, and ponds, but it can also be found in saltwater habitats like oceans. Nematoproctus causes various diseases in fish, including pneumonia, giardiasis, and amoebic colitis.