Ionic Effects of Infection of Ichthyophthirius multifiliis in Goldfish

Ichthyophthiriasis is a common parasitic disease of freshwater food and ornamental fish. This study examined the ionic effects of an induced infection of ichthyophthiriasis in goldfish Carassius auratus. The whole-animal net Na+ and Cl- fluxes were measured from 12 goldfish each day for 5 d. The numbers of branchial mucous and chloride cells were also determined histologically. Two days of postexposure to 200 theronts/mL resulted in significant net losses of Na+ and Cl-. Whole-body ionic effluxes were then reduced over the subsequent duration of the experiment. There was a general increase in the numbers of branchial mucous cells as reinfection progressed. Branchial chloride cells were elevated in infected fish, indicating some degree of compensation in response to infection. This suggested that acute ionic disturbances occurred in the host fish as a consequence of different stages of the life cycle of the parasite; the host exhibited a suite of physiological and morphological changes to compensate for parasitic infection.