In vitro secretion of metabolic end-products by piscine haemoflagellates Cryptobia salmositica and C. bullocki (Kinetoplastida: Bodonidae) and the relationship of these products to the pH in the medium.

Pathogenic and nonpathogenic strains of Cryptobia salmositica Katz, 1951 and C. bullocki Strout, 1965 produced hydrogen peroxide, pyruvate and lactate under in vitro conditions in Minimum Essential Medium (MEM). As parasite number increased, the phenol red in the medium changed from red to yellow. This change was not associated with a decrease in pH, or an increase in pyruvate or lactate, but was correlated with an increased secretion of hydrogen peroxide. Parasites incubated at 10 degrees C in medium at pH 6.0, 6.5, 7.0 and 7.3 were active for about I week with decreasing activity in the absence of serum. Parasites in saline (pH 6.0, 6.5, 7.0 and 7.3) were nonmotile within 24 h and were dead in about 1 week. This suggests that these Cryptobia spp. are sensitive to changes in pH and require medium which is buffered, either with serum or Hepes.