Studies on Consumption and Growth in the Ciliate Colpidium campylum Stokes

The study of animal energetics has gained momentum in recent years, involving both field approach and laboratory study. However, such investigations have largely bypassed the Protozoa, with the exception of the work of Heal (1967) on a species of Acanthamoeba, and those of Curds & Cockburn (1968, 1971) on the ciliate TetraXymena pyriformis Ehrenberg. The present study describes aspects of the energetics of the hymenostomatid ciliate, Colpidium campylum Stokes. When measuring growth and reproduction rates in a protozoan, and their relationship to the amount of food consumed, a complicating factor is that the food source itself is capable of rapid division given favourable conditions. Experimental design must allow for this division. The method chosen in the current study was first suggested by Heal (1970), and involves using a non-nutrient medium and measuring the number of bacteria and Protozoa present at the beginning and the end of a specified time. The present study appears to be one of the first in which the actual energy content of both bacteria and Protozoa have been used to calculate gross growth efficiency, i.e. the quantity of ingested food that is incorporated. Heal (1967) used dry weight when estimating the conversion efliciency of Acanthamoeba sp., fed on yeast cells, as did Curds & Cockburn (1968) with TetraXymena pyriformis.