Artificial culture of Labyrinthuloides haliotidis (Protozoa: Labyrinthomorpha), a pathogenic parasite of abalone

Abstract

Labyrinthuloides haliotidis was isolated from infected abalone (Haliotis kamtschatkana) and successfully cultured in minimum essential medium with 10% fetal calf serum at 10 °C for at least 1 year. On transfer to sea water, some subcultures produced numerous motile biflagellate zoospores while zoospore production of other subcultures was poor. On return to minimum essential medium, zoospores transformed into rapidly dividing vegetative forms. Labyrinthuloides haliotidis was not fastidious in its nutrient requirements and vegetative forms grew well in several different liquid media, on agar containing 10% bovine serum, and on pine pollen (Pinus contorta) in sea water. The mean diameter of the round vegetative forms often varied significantly (Student's t-test, P < 0.05) but the overall range in diameter (3.1 to 16.2 μm) observed in the various media was similar. Best growth occurred at 10 °C and in media made up with 30‰ sea water. No growth occurred at 28 °C or above, or in thioglycollate culture medium at 10 °C. Although L. haliotidis grew on pine pollen in sea water, zoosporoblasts and zoospores were not produced. The disappearance of precipitated proteins in agar medium around colonies of L. haliotidis and the destruction of host tissue around the parasite in infected abalone suggest that extracellular digestion occurs with this organism.