The unicellular organisms, Spirostomum also undergo changes on habituation. Spirostomum are ciliated protozoa and habituation helps in studying behavioral changes in these parallel to habituation. But it is viewed as a process to filter out iterative stimuli with no significant changes. And the easiest way to judge the changes is that as habituation is a homeostatic process it optimizes the Spirostomum's likelihood of judging the importance of the stimulus in a new iterative series or a change in it.
The method to detect the low or high responsiveness to the stimuli is that if we take the initial responsiveness as organism's threshold prior to stimulus occurrence then if it has high initial response it is said to have lower threshold and if low initial response visa versa. In Spirostomum the time course of contraction is very rapid with 4 to 5 mS as the cells contract at a rate in excess of 100 cell lengths sec-1. And as the stimulus strength duration judges the threshold response, Spirostomum is said to have full or no contraction at all. The changes in resting membrane potential do not cause initial contractions while microinjection of calcium buffers induce contractions.
The Spirostomum are habituated to a mechanical shock and cause brief contractions. And as the stimulation is repeated the number of contractions decreases. Ribonucleic acid (RNA) and protein have also been found to increase during habituation as per the foundations of Applewhite, Gardner and Lapan. As the RNA and protein increases occur after a few consecutive stimulations RNA and protein inhibitors can also be used in combination. Though large amounts of RNA and proteins are not needed for habituation in protozoan Spirostomum.
For the process of habituation firstly place the individuals on the slide. Tap the slide with mechanical stimulus every four seconds. You'll notice a change in Spirostomum behavior after 12 to 20 stimuli. The calculation of the percentage of the protozoa contracting can be done by counting from photographs taken during the process. Various studies have shown that Spirostomum can remember for ten minutes maximum.
The term behavior is used to extend the original meaning to the concept of primary internal processes and changes occurred due to habituation in single cellular organisms. It includes their iterative external stimulation, their initial threshold to the initial stimulus and the behavioral changes in them. The shorter life span of habituation in Spirostomum also suggests that synthesis of macromolecules may not be necessary. Therefore, the adaptive significance of habituation in Spirostomum as viewed across the science of phylogeny.
Sources / References:
1) Smith. James, Eisenstein. E.M., Eisenstein. D. Research & Development. Federal Bureau of Investigation, Los Angeles, CA. The Evolutionary Significance of Habituation and Sensitization Across Phylogeny: A Behavioral Homeostasis Model.
2) The Department of Zoology. University of Hul. Hawkins. R.B. < http://www3.interscience.wiley.com>
3) http://www.nature.com. Journal.
4) Applewhite and Gardner (1968). Applewhite, Gardner and Lapan(1969)
7) Protein and RNA Inhibitors and Protozoan Habituation. Gardener. Frank.T, Applewhite.