Reactions of Stentor coeruleus to certain substances added to the medium.

Abstract This study has shown that in the large ciliate Stentor coeruleus with its highly differentiated cortex the different components and derivatives of the ectoplasm react in specific and selective ways to various chemicals added to the medium. When lethal concentrations of the chemicals are used, these effects can be produced within a few minutes without further complications; and by watching the protozoa during the time prior to disintegration and returning them to normal medium at successive intervals, cells can be obtained which have suffered specific deletions from which they can recover. Perhaps the most striking reaction produced was the selective shedding of the peristome and of its precursor, the differentiating oral primordium. How and why this occurs we cannot yet say, but the variety of chemicals which produced this effects seems to preclude certain lines of interpretation. That the effect was not ionic was shown by the fact that sugars also produced it and the reaction did not vary with the valency of ions in the salts tested. Similarly, the reaction apparently is unrelated to viscosity since Heilbrunn [6] showed that mono- and bivalent ions have opposite effects on the consistency of endoplasm and ectoplasm in S. coeruleus. The effect was probably not osmotic because very weak, non-hypertonic solutions of Na2CO3 and strychnine sulfate also produced peristome shedding, and in strong sugar solutions the peristome was sloughed long before the cell showed any sign of collapse due to osmosis. Hydrogen ion effects were ruled out because neutral substances were effective in producing this response. It would probably not be reasonable to regard sloughing of the adoral band as an autotomy since extreme mechanical injury does not produce it. The fact that ethyl alcohol alone of all the compounds tested had the opposite effect of causing initial destruction of the general body ectoplasm and never a shedding of the peristome may afford a clue toward the eventual explanation of this phenomenon. The finding that sublethal concentrations of certain salt mixtures, sugar, and LiCl can cause complete or partial inhibition of the development of the oral primordium relates the effects of chemicals on Stentor to the vast problem of cell differentiation. Oral regeneration in stentors can also be inhibited by antisera (unpublished) as well as by anti-metabolites like acriflavin [20]; and incomplete, astomatous development of the oral primordium occurs in certain strains of S. coeruleus under normal conditions of culture, possibly because of genetic peculiarities [17]. It is likely that these lines of investigation will prove to be mutually illuminating. A connection between morphogenesis and the reactions of Stentor to chemicals is further indicated by the fact that lithium produces special effects in this ciliate as it does in embryogeny. Suppression of both differentiation and dedifferentiation of feeding organelles of the “head” in Stentor, accompanied by a structural broadening of the cell which can tentatively be attributed to a stimulation of the multiplication of the lateral pigment and ciliary stripes, might be regarded as a result in this protozoan comparable to vegetalization in the sea urchin embryo. Shedding reactions in respect to the pigment granules (mitochondria?) and outer layer of the cell membrane of Stentor, as well as specific effects on the behavior of the ciliary membranelles of the peristome were described. Besides posing interesting problems in themselves, these reactions provide a simple means of selective operation on cytoplasmic differentiations in this ciliate. It should be interesting to follow with electron microscopy the structural changes in the cortical differentiations of Stentor as affected by those chemicals which produced the most clear-cut reactions, and the fact that iodine salts were found to be perfect myoneme anaesthetics may make it possible to obtain suitable preparations for this purpose.