Establishment of mixed culture probiotics and microalgae as food for bivalve larvae

Studies were carried out to establish the feasibility of incorporating bact eria with the ability to produce inhibitory substances (BPI) into axenic cu ltures of Isochrysis galbana with the object of using this microalga as a v ector for transmitting BPI into cultures of larval bivalves as antagonists of pathogenic bacteria in these cultures. As a first step, the ability of s even strains of BPI to grow in extracellular products of I. galbana was eva luated, with positive results with four of these (334, C33, 11 and 77). Sub sequently, the effect of the addition of these strains on the growth of I. galbana was evaluated, Comparison of growth rates of I. galbana with and wi thout the addition of BPI showed no significant differences (P > 0.05). A s table and persistent inhibitory capacity of strain C33 on the pathogen Vibr io anguillarum was also observed. Finally, studies were made on the ingesti on of BPI by larvae of Argopecten purpuratus (Lamarck 1819), Results demons trated a significant ingestion of strain 11 (P > 0.05), when it was inocula ted directly into the water, and bacterium C33, when delivered in conjuncti on with the microalga, Upon evaluating incorporation and maintenance of BPI strains 11 and C33 after 5 days of larval culture, we observed the major p resence of strain C33 (3 x 10(2) cfu/larva) compared with strain 11 (90 cfu /larva), The results obtained suggested that it was feasible to use microal gal cultures as vectors for the introduction of bacterial antagonists to ba cterial pathogens in molluscan larval culture.