What does Paramecium use for defense?


Trichocyst (trick-o-sists) is a small spindle-like organelle situated in the ectoplasm with a minute pore opened on the pellicle surface. Trichocysts are arranged perpendicular to the ectoplasm. Trichocysts are filled with a dense refractive fluid containing swelled substances. When the paramecium cells receive mechanical, chemical, or electric stimuli, trichocysts discharge their contents and become long, thin, stinging spikes. After they are discharged, new ones are generated from kinetosomes.

The exact function of trichocysts is not quite clear, though a popular theory is that they are important for defense against predators. Trichocysts may also help cell adhesion and support the paramecium cell body.

Paramecium Cell Structure

[In this figure] The anatomy of a Paramecium cell.

Trichocyst paramecium

[In this figure] Trichocysts of Paramecium.
Trichocysts are spindle-like organelles that can discharge stinging filaments as protection against predators. Left: A TEM image showing a trichocyst embedded in the ectoplasm. When receiving outside stimuli, the core of trichocyst will swallow and push the spike out from the sheath. (Image:  Bannister, J. Cell Sci. 11:899-929, 1972.) Right: Highly magnified phase-contrast image showing a paramecium fired its spiky trichocysts for protection. (Image: Walter Dawn, Encyclopædia Britannica)

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The Structure of Paramecium Cell

The Structure of Paramecium Cell

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