Ultra-high-density culture of the rotifer Brachionous rotundiformis using a membrane filtration unit and its effect on bacterial abundance in the rotifer body [Japanese]

摘要

We have developed a novel culture system designed for ultra-high-density production of the so-called S-type marine rotifer (Brachionus rotundiformis), which has become an indispensable initial food item for larval cultures of marine fishes and crustaceans. In our culture system, a membrane-type micro-filtration unit (pore size was 0.4 mum) was incorporated in a culture tank (40 l) to prevent accumulation of NH4+, which is a strong inhibitor of rotifer growth. In rotifer batch culture tests with and without the culture system, freshwater Chlorella paste (Chlorella regularis; packed vol., 600 ml/l) was fed continuously into the culture water using a peristaltic tube pump at feed rates from 3.8 - 8.0 l/tank/d. Oxygen gas (purity, 90%) was fed at a rate of 0.2 vvm. In the batch culture system with the filtration unit, the culture broth was filtered out through the unit and fresh seawater was supplied to maintain the culture volume in the tank. In batch culture without filtration, the rotifer density reached 40,000 rotifers/ml after 2 d. However, the rotifer density subsequently seriously decreased due to an increase in the NH4+ concentration up to 900 ppm. In contrast, in the culture with filtration the NH4+ concentration remained below 240 ppm after 4 d, and as a result the rotifer density reached 160,000 ind./ml. The population of Vibrio sp, in the rotifer body diminished from 10(9) to 10(3) CFU/g-rotifer as a consequence of using the filtration unit.