Cellular component
Trichocyst
| Definition | The trichocyst is an architecturally complex secretory granule having a highly constrained shape docked at specialized cortical sites in Paramecium and other ciliates. Each cell bears about 1'000 trichocysts, which are supposed to be defensive organelles against predators. Trichocyst consists of a spindle-shaped body bearing at its wide end a tip often compared to an inverted golf tee. An external stimulus can trigger massive and synchronous exocytosis. After exocytotic membrane fusion, contact with the H2O and calcium ions in the external medium leads to an extremely rapid (< 50 ms) and irreversible expansion of the trichocyst contents, to yield a second, needle-shaped form which remains insoluble. |
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| Category | › Cellular component
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| GO | › trichocyst [ GO:0055039 ]
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