OBSERVATIONS ON THE FOOD HABITS OF ENTAMOEBA MURIS AND ENTAMOEBA RANARUM

¹ From the Zoölogical Laboratory, University of Pennsylvania, and the Marine Biological Laboratory, Woods Hole, Mass.

On the basis of observations on fixed and stained slides showing Entamoeba muris and E. ranarum, the following observations and interpretations have been made.

In general, these species of Entamoeba show great diversity in the kinds of food ingested. E. muris more commonly feeds on a fusiform bacillus but its diet includes many other types of bacteria, Blastocystis, yeasts, plant filaments, starch grains, Trichomonas, Chilomastix, Hexamitus, and host erythrocytes, leucocytes and epithelial cells. E. ranarum shows a similar range of food objects.

Individuals often select for a time, at least,—a single kind of food, with which they may engorge themselves. Others are more omnivorous in their selection.

Populations from a single host may show decided preferences for one type of food; for example, about 80 per cent of one population of E. muris contained one or more specimens of Trichomonas.

A diversity of methods of ingestion is indicated. Starch grains are surrounded by enveloping pseudopodia without the formation of a fluid-containing vacuole around them. Trichomonads appear to be drawn through an ingestion tube with walls sufficiently differentiated to stain heavily with iron hematoxylin. Plant filaments are taken in through similar tubes some of which show the deeply-stained walls. There is evidence that differentiated tubes are employed to constrict food bodies into smaller units.

Bodies which stain with iron hematoxylin have been seen in contact with ingested starch grains in E. muris. These are interpreted as digestive granules in the sense that this term is used in the review by MacLennan (1941).