Fundamental Studies on Physiology of Rotifer for its Mass Culture—I: Filter Feeding of Rotifer

Abstract

In the present study, the filtration rate and the ingestion rate of the rotifer, Brachionus plicatilis, were investigated under various culture conditions. Several groups of the rotifer varying in density were cultured for 60 min, in an experimental medium containing a species of marine Chlorella at a definite density. The filtration and ingestion rates of the rotifer were then estimated by measuring the optical density of Chlorella as the phytoplankton density in the media. The rotifer used in these experiments was pre-cultured in two ways. In one case the rotifer was made to have food in its stomach by feeding in the experimental medium (satiated condition) and in the other case the rotifer was made to have an empty stomach (empty condition). Results obtained are as follows. 1. When the rotifer is fed with Chlorella in the test medium kept at a density of less than about 213 xlO4cells/ml, the rotifer maintained its filtration rate at the highest and almost constant level of about (7—10) x 10~5(empty condition) and (5–7) x 10–5 ml (satiated condition) per min. per individual while the ingestion rate continued to increase. Above this density of Chlorella, the filtration rate decreased with the increase of the density of Chlorella in the test medium while the ingestion rate maintained an almost constant level of about 200 cells/min/individual under the empty condition. This tendency of ingestion rate could not be observed distinctly in the rotifer under the satiated condition. 2. The filtration rate measured under the satiated condition showed its highest in the media having a temperature over 22.0°C, chlorinity at about 7.8%