What is the Difference Between Cnidocytes and Nematocysts?

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Cnidocytes and nematocysts are both associated with the stinging cells found in cnidarians, such as jellyfish, corals, and sea anemones. The main differences between them are:

  • Cnidocytes: These are explosive cells that contain a giant secretory organelle called cnida. Cnidocytes are present in the epidermal layer of the organism and are used for defense and capturing prey. They are also known as cnidoblasts or nematocytes.
  • Nematocysts: These are specialized sub-cellular organelles (part of the cell) present in cnidocytes. Nematocysts are bag-like, globular-shaped structures that contain a coiled thread-like structure at the base, with a hair-like structure called a cnidocil on the outside. When triggered, the tubular shaft of the nematocyst is ejected, and the cnidocil may act as a trigger for the thread-like coiled structure. Nematocysts are used to catch prey and defend against predators.

In summary, cnidocytes are the stinging cells that contain nematocysts, which are the secretory organelles or stinging capsules present in the cnidocytes.

Comparative Table: Cnidocytes vs Nematocysts

Cnidocytes and nematocysts are specialized cells and organelles found in cnidarians, such as corals, jellyfish, and anemones. Here is a table highlighting the differences between them:

Feature Cnidocyte Nematocyst
Definition An explosive cell containing a giant secretory organelle called cnida. A specialized sub-cellular organelle present in cnidocytes.
Function Cnidocytes are used for catching prey and defending against predators. Nematocysts are the secretory organelles or stinging capsules in cnidocytes.
Location Cnidocytes are present in the exodermal layer of the organism, such as the tips of tentacles. Nematocysts are found inside cnidocytes.
Structure Cnidocytes have a sensory trigger, such as a cnidocil or a cone. Nematocysts have a bulb-shaped capsule containing a coiled thread with barbs.
Types Cnidocytes can be of penetrant, glutinant, volvent, or ptychocyst variety. Nematocyst is a penetrant variety of cnidocyte.

In summary, cnidocytes are specialized cells that contain nematocysts, which are the stinging organelles. Cnidocytes are used for capturing prey and defending against predators, while nematocysts are the secretory organelles that eject a coiled thread with barbs to penetrate the skin of prey or predators.