Ultrastructure of the Peritrich Ciliate Ambiphrya ameiuri and Its Attachment to the Gills of the Catfish Ictalurus punctatus1

Ambiphrya ameiuri is an ectocommensal peritrich that attaches to the gills of warm-water fishes and filters bacteria from the water. The ultrastructure of this protozoon, its attachment to the fish gills, and its effect on the gill tissue were investigated by scanning and transmission electron microscopy. The peritrich attached to the gills by fibers extending from the scopula. A microtubular array, apparently a barren kinetosome, was present in each lobular projection, but no scopular cilia were observed. At low densities Ambiphrya had no apparent harmful effects on the fish; however, at high densities respiration may be impeded. Ultrastructural studies indicate that this organism receives no nourishment from the host tissue.