The Digestion of Oils by Amoeba dubia.

Abstract

The following account deals with experiments consisting of injection of various oils in one of the large free-living amoebae (Amoeba dubia). 1 Injection was accomplished with a Chambers micro-manipulator. The experimental amoebae were from a race which has been cultivated by one of the authors for 4 years. Thus a minimum of variability has been ensured in the amoeba protoplasm concerned. Selected individuals were isolated and injected in the usual hanging drop. They were transferred singly to depression culture dishes. The diameter of the injected oil drop was measured by a calibrated ocular micrometer. These measurements were taken daily until droplet was either extruded or completely digested. Where extruded it was invariably located in the culture medium and measured for decrease in volume. Both experimental and control animals were placed in non-toxic distilled water from the same source as that used for the mass culture of the amoebae.

Nine representative oils were used: animal, vegetable and mineral, which were chosen with reference to their suitability for this type of microinjection. All of these oils were injected in the natural condition and 4 were also injected after radiation by an ultra violet lamp (mercury arc) for 20 minutes at a distance of 24 inches. The amount of digestion accomplished in the various oils is expressed in cubic micra. The average volume of an amoeba was determined by the following method: An amoeba crawling normally was regarded as a thin cylinder. The area was computed from camera lucida drawings, at appropriate magnifications, of 20 typical amoebae. A polar planimeter was used in making the computation. The thickness of the amoeba was measured directly by placing crawling amoebae on a coverslip and viewing the animals edgeways. By this means the volume of an amoeba was found to be approximately 500,000μ³. The injected oil was considered as a sphere and the different volumes computed from the measurement of the diameter. The following table summarizes the results of the injection of this series of oils in Amoeba dubia:

The relative digestibility of these oils by Amoeba dubia may be summarized as follows: