To examine whether P. leiognathi survives the passage through the digestive tract of A. annularis, a fish which previously had been starved for 24 h was fed with 20 glowing Artemia, washed with FSW, transferred to a 2-L plastic tank filled with FSW, and allowed to defecate overnight. In the morning the feces were washed thoroughly with sterilized FSW, torn apart using a sterilized needle, suspended in 1 mL sterilized FSW, and, after serial dilutions, were spread on seawater-based LB agar plates. The plates were incubated at 30 °C overnight, and the number of luminous cfu was determined. To assess the possibility that luminous bacteria were present initially in the gut of A. annularis, another fish was fed with 20 nonluminous Artemia, and its feces were analyzed similarly.