Relationship between Body Size of the Rotifer Brachionus plicatilis and the Maximum Size of Particles Ingested

Abstract

The maximum size of particles ingested by Brachionus plicatilis was investigated by the use of an automatic blood cell counter. The rotifer used in this experiments was determined to be var. spatiosus based on consideration of their dorsal lorica length. Dried and powdered activated sludge was utilized for simulating food particles. The size of the particles was expressed in terms of the diameter of a sphere of the same volume. Food particles were counted into twelve size sections between 29.5 μm and 13.6 μm, and the maximum one among those sections where particles were decreased through the filtering of rotifers was denoted as S_max. The lower end of S_max was assumed to be the maximum ingestable size. After obtaining the filtering rate (I) by all individuals and the one (I_a) only in S_max, I_s/I was calculated, which indicates the proportion of experimented rotifers having contributed to the clearance in S_max. Then, the individuals which ingests the particles of the lower end of Smax as the maximum igestable particles corresponds to the 100(I_s/I)th individual from the larger end among a hundred rotifers drawn randomly at the termination of an experiment. From the total ten experiments, a regression line Y=0.0896X-0.033, (r=0.94) was obtained between the lorica length (X μm) of the aforesaid animal and the maximum diameter (Y μm) of particles ingested.