H. Hirata, M. Wachi, S. Yamada, O. Murata, T. Nasu
Abstract:
Recently, a probiotic culture system for the fish has been developed in the sea farms. The present experiment was conducted to apply the system for the rotifer culture. The probiotic materials were made by the fermentation of head of yellowtail (Seriola quinqueradiata), green alga (Ulva pertusa), and lees of bean curd with "Uchishiro microorganisms". The microorganisms consisted of about 40 species of bacteria such as Bacillus subtilis, B. licheniformis, B. ereus, B. macerans, and so on. The culture medium was prepared by the re-fermentation with 50 g of the probiotic materials in one liter of 50% sea water. Strong aeration was supplied for 3 or 4 days. The water temperature was kept at about 25 C. The medium was used as food for the rotifer.
In order to know the optimum volume of medium as food for rotifer, 4 tanks were prepared; tank 1: 100 ml medium for 1 liter rotifers, tank 2: 20 ml medium for 1 liter rotifers, tank 3: 10 ml medium for 1 liter rotifers, and tank 4: no probiotic medium for the rotifers as control. Initial population densities of rotifers in all tanks were regulated to about 100 individuals per ml.
The higher population density, 351 ind/ml, of rotifers was found in tank 2 which were fed on 20 ml medium for 1 liter rotifers. The second higher density, >288 ind/ml, was observed in tank 3 which was fed on 10 ml medium for the rotifers. On the contrary, the population densities in tank 1 and 4 decreased day by day; it is understood that the probiotic medium is useful for rotifers if it is supplied in satisfactory volume.
(Faculty of Agriculture and Fisheries Res. Laboratory of Kinki University, 3327-204 Nakamachi, Nara, 631, Japan)
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