Feeding in the rotifer Brachionus calyciflorus : II. Effect of food density on feeding rates using Euglena gracilis and Rhodotorula glutinis.

The laboratory feeding behavior of Brachionus calyciflorus varies depending upon the type of food cell available in suspension. When feeding on the yeast Rhodotorula glutinis, rotifers show a continuous increase in ingestion with increased cell density between 0.01 and 1000 μg dry weight ml-1. Effective clearance rates drop from ca. 50 μl animal-1 h-1 to less than 0.5 μl animal-1 h-1 over this food density range. When feeding on Englena gracilis, B. calyciflorus ingestion rates are constant between 1.0 and 100 μg ml-1 of available food, averaging close to 25 ng animal-1 h-1. The decrease in clearance rate is more striking than with R. glutinis, dropping from 45 μl animal-1 h-1 at 0.1 μg ml-1 to 0.13 μl animal-1 h-1 at 100 μg ml-1. Differences between the patterns obtained with the two food types indicate fundamental dissimilarities in the feeding behavior of this rotifer species when presented with these different foods.