A FACTORIAL EXPERIMENTAL-DESIGN FOR INVESTIGATION OF THE EFFECTS OF TEMPERATURE, INCUBATION-TIME, AND PATHOGEN-TO-PHAGOCYTE RATIO ON IN-VITRO PHAGOCYTOSIS BY TURBOT ADHERENT CELLS

A complete second-order factorial design was used to investigate the e ffects of temperature (T), incubation time (t) and pathogen-to-phagocy te ratio (R) on in vitro phagocytosis of Glugea caulleryi spores by tu rbot spleen adherent cells. Two alternative indicators were used to qu antify phagocytosis: percentage phagocytosis (PP, i.e. the percentage of cells showing phagocytic activity), and the phagocytic index (PI, i .e. the mean number of ingested spores per phagocyte). Within the T, t and R ranges investigated, the fitted model for PP reached a maximum at T = 22 degrees C, t = 1.7 hr and R = 68:1, while the model for PI r eached a maximum at T = 22.8 degrees C, t = 1.85 hr and R = 85:1. Temp erature and spore-to-phagocyte ratio were the most important factors i nfluencing PP, while all three experimental factors had strong effects on PI.