Further observations on Cryptobia dahli (Mastigophorea: Kinetoplastida) parasitizing marine fish.

Studies were conducted primarily to ascertain the mode of transmission of Cryptobia dahli parasitizing the digestive tract of lumpfish (Cyclopterus lumpus). Another flagellate, morphologically similar to C. dahli, was also observed in the gut of a deepsea fish (Macrourus berglax). Several invertebrates, which are food for lumpfish, were examined for flagellates, but were neither infected nor showed evidence of cystic stages. Parasites were more abundant in the stomach, especially at about pH 5, than in other areas of the digestive tract. Transmission was achieved by pipetting the parasites into the stomach of uninfected fish, by feeding food contaminated with flagellates, and also by holding infected and uninfected fish in the same aquarium. In nature, lumpfish probably acquire parasites during winter when they aggregate and regurgitate into seawater because parasites can survive for short periods outside their host.