The organelle in protists used as a defense mechanism by discharging threads is called what?

• A. Trichocyst
• B. Contractile vacuole
• C. Cilia
• D. Flagella

Answer: (A)

Extrusive defense in some protists comes from specialized secretory organelles that eject threadlike filaments when the cell is threatened. These structures, called trichocysts, are housed in capsules just beneath the membrane and release a long thread quickly in response to stimulation, helping to deter predators or entangle prey. Other common protist features don’t serve this defense purpose: contractile vacuoles manage water balance, while cilia and flagella are used for movement and feeding. So the organelle that discharges threads for defense is the trichocyst.