Application of autochthonous Bacillus bioencapsulated in copepod to grouper Epinephelus coioides larvae

Probiotic administration to fish larvae via live feeds such as rotifers and Artemia has been reported extensively. However, no information is available about the application of probiotics via copepods, one of the most appropriate live feeds for many marine fish larvae. This study evaluated the application of autochthonous probiotic Bacillus clausii DE5 and Bacillus pumilus SE5 bioencapsulated in copepods to orange-spotted grouper Epinephelus coioides larvae. The larvae were fed with control copepod (Pseudodiaptomus annandalei) or probiotic-enriched copepods from day 40 to day 68 after hatching. Increased total length and body weight were observed in larvae fed with the two probiotics for 14 days. The improved growth may be related to the enhanced activities of intestinal digestive enzymes, such as alkaline phosphatase and acid phosphatase. Improved survival was also observed in probiotic fed larvae and may be associated with changes in immune defense, as evidenced by increased lysozyme and SOD activities. On the other hand, several potentially pathogenic bacteria such as Aliivibrio fischeri, Vibrio scophthalmi and Vibrio sp. were suppressed and a desirable gut microbiota was induced by probiotic B. clausii DE5 and B. pumilus SE5, which may contribute to the improvement of health and the development of gastrointestinal (GI) tract in larval grouper E. coioides. Therefore, our results suggest that copepod (P. annandalei) is suitable to act as vector of probiotics in marine fish larvae.

► Copepods are suitable to act as carriers of probiotics in grouper larvae.
► A balanced microbiota induced by probiotics benefits larval health and digestion.
► Increased growth may be related with intestinal digestive enzymes.
► Improved survival may be associated with increased immune defense.