A marine probiotic treatment against the bacterial pathogen Vibrio coralliilyticus to improve the performance of Pacific (Crassostrea gigas) and Kumamoto (C. sikamea) oyster larvae

Abstract

Oyster larvae reared in hatcheries on the U.S. West coast often experience severe Vibrio coralliilyticus-related mortalities early in their development. Current treatment options for these molluscs are either not available or feasible; however, for decades, probiotics have been successfully used in finfish and crustacean shellfish culture. Consequently, the objectives of this work were to 1) isolate marine bacteria from oysters and evaluate their protective activity against Vibrio coralliilyticus infection of Pacific oyster (Crassostrea gigas) larvae, and 2) to determine the long-term effects of probiotic additions on growth and metamorphosis of larval Pacific and Kumamoto oysters (C. sikamea). A combination of three probiotic strains applied once 24 hours post-fertilization was more effective in improving survival of larval C. gigas exposed to lethal concentrations of V. coralliilyticus strain RE22, compared with separate additions of individual probiotics. In addition, a single application of the probiotic combination to one-day-old larvae increased the larval metamorphosis success of C. sikamea and both the Midori and Myiagi stocks of C. gigas. These results suggest that probiotics are effective at preventing bacterial infections and can significantly improve performance of oyster larvae, using a single application early in their development. Highlights* A combination of marine bacteria improved survival of Pacific oyster larvae exposed to virulent V. coralliilyticus. * Metamorphosis was increased after adding a single dose of probiotics to one-day-old larvae. * Repetitive dosing after each water change was not superior to a single dose one day post egg-fertilization. * A single dose of the probiotic combination resulted in larger size on day 12.