A Preliminary Note on Tetramitus, a Stage in the Life Cycle of a Coprozoic Amoeba

In 1920 a study of the Entamoeba of the rat was begun and in a culture on artificial medium a number of Coprozoic amoeba appeared, one of which exhibited a flagellate phase which seems to be identical with Tetramitus rostratus Perty.t The appearance of flagellate phases in cultures of Coprozoic amoeba (Whitmore,2 etc.) as well as of soil amoeba (Kofoid,3 Wilson,4 etc.) has been recorded a number of times, but the flagellates which appeared were relatively simple in organization and very transitory in occurrence. Furthermore, some of the simpler flagellates have been observed (Pascher5) to lose their flagella and become amoeboid. In the case here described, however, there is a transformation of a simple amoeba inlto a relatively complex flagellate which multiplies for several days then returns to the amoeboid condition and becomes encysted. Tetramitus rostratus has been studied by a number of investigators since its discovery in 1852, by Perty,1 yet no one has given a full account of its life history. The lack of cyts in previous accounts, mentioned by Dobell and O'Connor,6 is explained by the transformation into an amoeba before encystment. It is believed that this animal presents the extreme in transformations of this sort and'serves to emphasize the close relationship between amoebae and flagellates, and the need for careful studies of life cycles, in pure cultures where possible, in'investigations of coprozoic and other Protozoa. It is proposed to rec0rd at this time a brief account of the life history of this amuoebo-flagellate reserving tlle more extended discussion for future publication. The amoeba in question was first observed on November 5, 1.920 in coecal material which had been taken from the rat and placed in sterile physiological saIt solution on October 28, 1920. This is known as culture 10. After discovery of the amoeba, transplants were immediately made in various media. The amoebae were subcultured several times on solid media over a period of about two months, then two cultures were made in fluid media. In on the formula given by Sellards,7 namely, 1.0 gr. Witte's peptone, 0.5 gr. lactose, 1000 cc. distilled water was used; in another, dextrose was substituted for lactose in Sellards' formula. The medium containing dextrose proved to be much more favorable for the amoeba under consideration. In these liquid media a flagellate appeared which is thought to be Tetramitus rostratus Perty.