Protoopalina from the intestine of a Discus.
Protoopalina
Protoopalina from the intestine of a Discus.
Protoopalina sp.This parasite is also mentioned under Nyctotherus
This organism is sometimes found as a commensal in the intestine of Discus (Symphysodon). Twenty years ago I sometimes found these in wild Discus and once in a (Metynnis). Recently they can be found in tank-raised discus from southeast Asia, as in the fish I examined here. An unusual occurance is to find them in Angelfish (Pterophyllum). They are fairly good size for a protozoan (100 to 200 micrometers) usually colorless and gliding slowly amidst intestinal contents. They are covered with long cilia (referred to as multiple flagella) which move continuously.
Protoopalina are in the family Opalinidae, which are in their own class Opalinata (not with the Ciliates). Other genera include Opalina, Cepedea, and Zelleriella. These are mostly commensals in amphibians. Some species are found in marine fish. It is difficult to say that these organisms do any damage to their host. It is said that they absorb nutrients from their surroundings and are often considered to be symbiotic with their host. Aquarium fish thought to carry these are usually treated with Metronidazole.
