Application of the minute monogonont rotifer proales similis de Beauchamp in larval rearing of seven-band grouper epinephelus

In comparison to the rotifer Brachionus rotundiformis, the euryhaline rotifer Proales similis has a much smaller body size (83 m in length and 40 m in width), and it may be applicable as live food for rearing marine fish larvae with a very small mouth size. A mass culture technique of P. similis was recently established, and it has already been confirmed that marine fish larvae could ingest P. similis. In the present study, we further investigated the use of P. similis as an initial food by observing larval ingestion and digestion and analyzing the nutritional profile, as well as through a 10-day larval rearing trial to investigate survival and growth. Seven-band grouper Epinephelus septemfasciatus larvae showed higher selectivity against P. similis than B. rotundiformis 4 days after hatching. The larvae digested and utilized P. similis as an energy resource as they grew, and survived until the end of the experiment. The fatty acid profile of P. similis changed according to the type of microalgae; Nannochloropsis oculata NIES2146 strain and “super fresh” Chlorella vulgaris V-12 (Chlorella Industry, Fukuoka, Japan) were used as food sources. Higher growth and survival during the initial 10 days were observed when P. similis and B. rotundiformis were co-fed to the seven-band grouper larvae.