Some Factors Governing Feeding Behavior of Homalozoon vermiculare (Ciliophora, Holotricha)

SYNOPSIS. Feeding activity of Homalozoon vermiculare on Paramecium and Blepharisma and on a number of non-living materials was compared in order to understand its feeding behavior and some of the factors governing it. During a given period it involves a series of feeding responses, each response being completed in 5 stages: (i) contact of prey or non-living particles with the oral rim of Homalozoon, (ii) ejection of toxin by Homalozoon, if the food is a living organism, (iii) paralysis of the prey, (iv) grasping, and (v) swallowing. The feeding activity of Homalozoon differs from one food to another and also on any one food at different times. These differences are governed by (i) the physiologic condition of Homalozoon and (ii) certain food characteristics. Its starvation, but not its developmental stage, markedly influences its feeding activity on any food. The food characteristics most important for feeding by Homalozoon are: (i) concentration of prey or non-living particles in the medium, insuring their adequate contact with the organism's mouth, (b) susceptibility of living organisms to paralysis by the toxin, (c) suitability of particle size for accommodation in the organism's mouth, and (d) suitability of the food material to stimulate the grasping and swallowing responses. Homalozoon much prefers Paramecium to Blepharisma on account of (i) a greater susceptibility of Paramecium to paralysis by the toxin, and (ii) certain differences in the chemical characteristics of the certain proteins, particularly albumins, hemoglobin, etc., of the 2 organisms.