ABSTRACT
Ichthyobodo necator or Costia necatrix as it is more commonly known is a very important protozoan parasite of cultured fish throughout the world. However, it is probably the major cause of death of cultured salmonid fry in Scottish fish farms; even the viral disease IPN seldom causes such acute mortality as does Ichthyobodo. Ichthyobodo necator was first described by L. F. Henneguy in 1883 and more fully in 1884 and he named it Bodo necator. The number of flagella which Ichthyobodo possesses and which caused so many problems for earlier workers has been shown to be two, one long and one short flagellum. Very little work has been carried out on the reproduction of Ichthyobodo. However O. N. Bauer has suggested that Ichthyobodo reproduces asexually by longitudinal division, the four flagella form recorded by several authors presumably being the predividing form.
