Exocytosis in Paramecium tetraurelia: Trichocyst Function in Prey-Predator Interactions
Abstract
The ciliophoran Paramecium tetraurelia, has large exocytotic (secretory) organelles called trichocysts. Although considerable work on the development, genetics and physiology of the trichocyst as an exocytotic organelle has been done, the function of the organelle is still unknown. One venerable hypothesis of trichocyst function is that its violent exocytotic release serves as a defense against predator attack. This hypothesis was tested in the laboratory through two types of experiments. The predator used in the research was Didinium nasutum, another ciliophoran. Wild-type tetraurelia, $51s, and a mutant conferring loss of trichocyst function, nd7, were used as prey. The first approach (competition survival) involved exposing mixtures of precise numbers of wild-type cells and mutant cells (unable to release trichocysts) to the predator. A fixed time for interaction between the two species was allowed and the surviving paramecia were isolated and tested for trichocyst function. Variations of this involved increasing the intensity of the predation while maintaining a constant prey population. The second set of experiments consisted of measuring the times required for successful predation. Search times were defined as the time from predator introduction to the point of successful attack (i.e. capture of prey). Handling time was the interval from the successful attack until total engulfment of the prey. If trichocysts serve to protect cells from predation, then normal cells should have a better chance for survival than cells unable to release trichocysts. Comparison of the results suggested that the competition survival experiments were the most appropriate for testing this hypothesis. Analysis of the data obtained through t-tests indicates that wild-type cells have a slight but significantly better chance of escaping predation than trichocyst-defective mutants. The results suggest that trichocysts may have a subtle role in defense, at least from certain kinds of predators.
Description
Program year: 1986/1987Digitized from print original stored in HDR
Citation
Eduardo, Ana M. (1987). Exocytosis in Paramecium tetraurelia: Trichocyst Function in Prey-Predator Interactions. University Undergraduate Fellow. Available electronically from https : / /hdl .handle .net /1969 .1 /CAPSTONE -EduardoA _1987.