A Laotian strain of the rotifer Brachionus angularis holds promise as a food source for small-mouthed larvae of freshwater fish in aquaculture

A very small strain of the freshwater rotifer Brachionus angularis (Laos strain) was isolated in Vientiane, Laos. We investigated the morphology as well as grazing and growth characteristics of this strain. The lorica of the Laos strain was round, 86.0 ± 4.9 μm (mean ± SD) in length, with a few small spines. These morphological characteristics make the strain an appropriate live food for small-mouthed larvae of freshwater fish. The rotifer's grazing rate on Chlorella vulgaris increased in a density-dependent manner up to approximately 10 × 106 algal cells ml− 1. The rotifer filtering rate was stable (ca. 100 μl per individual per hour [ind.− 1 h− 1]) at 0.5–10 × 106 algal cells ml− 1 and declined to 30–50 μl ind.− 1 h− 1 at a higher C. vulgaris density (20 × 106 cells ml− 1). In batch cultures, the rotifer strain grew well at 24 °C and 27 °C when fed with algal densities of 7 × 106 and 10 × 106 cells ml− 1; under these conditions, the rotifer density reached > 2000 ind. ml− 1 within 10 days. Life history parameters were obtained using the individual culture method. The generation time became shorter at higher temperatures and higher algal densities.