Effects of several cultivation temperatures on miniaturization of the rotifers, Brachionus plicatilis

The rotifer, Brachionus plicatilis, is widely utilized as a starter feed in aquatic animal larviculture due to its optimal size, rich nutritional profile, rapid reproductive rate, and strong environmental adaptability. However, current aquaculture industry requirements reveal an unmet need for smaller rotifers to accommodate certain larval species with more restrictive gape limitations. To obtain smaller rotifers, this study investigated the effects of several cultivation temperatures, including 21 °C, 24 °C (control group), 27 °C, 30 °C, 33 °C, 36 °C, and 39 °C, on the miniaturization of B. plicatilis s.s. By measuring indicators such as survival status, body size, population growth rate, and nutritional value, we systematically screened for the optimal temperature to induce miniaturization of B. plicatilis s.s. and preliminarily analyzed the potential causes of size reduction at this temperature. The results showed that rotifers in the 39 °C group all died while rotifers in the other groups exhibited good survival. The body sizes of rotifers in the 27 °C and 30 °C groups were significantly smaller than those in the other four temperature groups. The population growth rate of the 30 °C group was significantly higher than those of the 27 °C and 33 °C groups, while the population growth rates of the 27 °C and 33 °C groups were significantly higher than that of the 24 °C group. Rotifers in the 30 °C group exhibited the highest contents of ARA and EPA, the second-highest DHA content after the 24 °C group, and comparable or significantly higher amino acid levels than those in the 24 °C group, except for proline and methionine, while the 27 °C and 33 °C groups showed lower contents of these substances compared to either the 24 °C or 30 °C groups. The above results made the 30 °C group stand out. What’s more, the 30 °C group exhibited a significantly shorter pre-reproductive period and higher fecundity than those of the 24 °C group. In conclusion, 30 °C is the optimal temperature for inducing miniaturization of B. plicatilis s.s., and the temporal and energetic allocation between growth and reproduction may be the key factors influencing temperature-dependent size variation.