Utilizing Brachionus biodiversity in marine finfish larviculture

Mouth gape sizes of marine finfish larvae determine the size of rotifer prey that can be ingested, so providing appropriate size rotifers controls the success of larval rearing. It is difficult for hatcheries to maintain pure cultures of multiple rotifer species by long-term serial dilution without cross-contamination. In this paper, we describe a technique for utilizing multiple rotifer species in larviculture that uses rotifer diapausing eggs as inocula, enabling hatcheries to supply larval predators with optimally sized rotifers. Biodiversity in the Brachionus plicatilis species complex is extensive, including considerable variation in body size. In this paper, we show that large quantities of diapausing eggs can be produced from many Brachionus species. Using the full range of body size diversity from seven Brachionus species, we can produce adult female rotifers with mean body lengths as small as 137 μM, or as large as 305 μM, and neonate females with body lengths ranging from 103 to 206 μM. The length of diapausing eggs for small Brachionus species averaged 100 μM, and 166 μM for large species. Diapausing egg production varied by 3.6 fold among 14 strains. Using diapausing eggs of the very small rotifer Proales similis (88 μM) to inoculate mass cultures also is described.