Studies of the contractile response in the protozoan, Vorticella picta.

Four experiments explored the contractile response ( ConR ) of Vorticella picta , a stalked ciliate. Repetitive mechanical stimulation decreased the probability of a “normal” ConR , increased the frequency of no response , and changed ConR topography. Repeated mechanical stimulation also reduced the ConR period (i.e., time needed for the subject to contract and then uncoil to the fully extended feeding state), and this effect occurred long before the no response and topographical changes began to occur. A stimulus elicited either a ConR or no response depending on whether the organism was fully extended or was in the process of extending from a previous ConR .