Defensive function of trichocysts in Paramecium

Abstract

A putative defensive function of trichocysts in Paramecium has been tested experimentally. Cells of trichocyst-non-discharge (tnd) mutant, artificially induced trichocyst-deficient cells, and intact wild-type cells were compared as prey for a carnivorous ciliate, Dileptus margaritifer. Cells of tnd mutants were eaten 9-45 times faster than wild-type cells by the predator in P. caudatum and P. tetraurelia. Encounters between paramecia and dilepti occurred in nearly the same frequency in mutant and wild-type cells. Paramecia with reduced numbers of trichocysts were obtained in P. caudatum, P. jenningsi, and P. tetraurelia by treating wild-type cells with lysozyme, a n inducer of trichocyst discharge. These cells were eaten faster than intact cells by the predator and the rate of predation was inversely correlated with the remained capacity of trichocyst discharge. It was concluded that the discharge of trichocysts defends these species of Paramecium against D. margaritifer. Therefore, the results of this work strongly support the hypothesis that trichocysts in Paramecium function as defensive organelles against predators. The results also support the hypothesis that the offense-defense interaction between Dileptus and Pramecium is mediated by their extrusomes (toxicysts and trichocysts) and suggest that extrusomes in ciliates function as organelles for interspecific cell-cell interaction.

One-way calcium spill-over during signal transduction in Paramecium cells: from the cell cortex into cilia, but not in the reverse direction

“…In a more complicated situation, when a Paramecium cell meets a predatory organism, the first reaction is expulsion of elongate trichocysts to keep the predator at a distance, as first shown by Harumoto and Miyake [76] and in more detail by Knoll et al [44]. The concept of a defensive function of trichocyst expulsion [76] can be supplemented by the observation that this is followed with little delay by ciliary reversal [44].…”

Calcium in ciliated protozoa: Sources, regulation, and calcium-regulated cell functions

“…Surprisingly, comparison of time constants shows that Paramecium can operate its stimu-lated exo-endocytotic system faster than any other dense-core-vesicle system. This may be vital for the cell, enabling it to use trichocyst exocytosis for defense against a predator, as first shown by Harumoto and Miyake (1991). Locally released trichocysts may act as a spacer to ward off the attacker, while the cell switches to "back gear" by subsequent ciliary reversal and, thus, escapes with very high efficiency (Knoll et aL., 1991b).…”

Selective predation by a harpacticoid copepod on ciliates in phytotelmata: a laboratory experiment

“…special organelles that extrude explosively in response to mechanical or chemical stimuli. Haramuto & Miyake (1991) have demonstrated that Paramecium trichocysts ensure effective defence against a predatory ciliate Dileptus margaritifer. Recently, Buonanno et al (2013) provided evidence that trichocysts of Paramecium tetraurelia were also efficient against some metazoan predators such as the rotifer Cephalodella sp.…”