Cnidocyte vs Nematocyst: Difference and Comparison

All the fauna species (even flora) have a defence mechanism against their predator species and non-friendly stimulus.

It doesn’t matter if it is the marine, terrestrial or aerial species; every organism ranging from the smallest organisms like amoeba to the blue whale,

the biggest living species on earth have these mechanisms to reduce the chances of getting attacked and are used even to find food.

One of the quickest defence mechanisms is found in the phylum Cnidaria, constituting the species like jellyfish, Portuguese man-o-war, sea anemones, and corals. It consists of Cnidocyte and Nematocyst.

Key Takeaways

  1. Cnidocytes are specialized cells found in the tentacles of some aquatic animals, while nematocysts are the stinging organelles within cnidocytes.
  2. Nematocysts are used for defence and capturing prey, while cnidocytes can also be used for adhesive purposes or to create a protective shell.
  3. Both cnidocytes and nematocysts are found in cnidarians, such as jellyfish and corals, but not all cnidarians possess nematocysts.

Cnidocyte vs Nematocyst

The difference between a cnidocyte and a nematocyst is that the cnidocyte assists the thread, cnidocil, to eject with the help of the nematocyst that propels it out and into the waters.

Cnidocyte vs Nematocyst
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Cnidocyte is a capsule present on a cnidarian’s body that ejects thread-like projections as a defence mechanism. It not only allows the organism to escape danger but also assists in hunting for food and adherence to the substratum during locomotion.

As soon as the species senses danger, the capsule makes the cell explode and release the hair-like cnidocil, which is not only a mechanical but also a chemoreceptor. This action occurs in milliseconds injecting an enzyme to stun or injure the predator.

On the other hand, a Nematocyst is the explosion cell (a subcellular structure or organelle) that ejects the cnidocil; the hair-like projection is released when the trigger is activated, containing venom that also helps in locomotion.

However, this function is enabled after a certain time. It only works when the organism has matured. The cells that produce nematocysts are called nematoblasts.

Ewer, in 1947 defined the functional categories of nematocysts as prey capture (penetrants), defence (solvents), and adherence during locomotion (glutinous).

The nematocysts contain the barbed or venomous coiled thread that is released at times of emergency. The string contains hypnotizing, a mixture of phenols and proteins.

Comparison Table

Parameters of ComparisonCnidocyteNematocyst
StructureIt is an inverted cell.It is a bag-like globular structure.
PresenceIt is present in the skin of the species.It is present inside the cnidocyte.
Further DivisonIt consists of cnida, cnidocyst, nematocyst, ptychocyst, and spirocyst.It is a cell present in the capsule containing the thread.
FunctionTo assist the nematocyst in ejecting the sting/hair.To eject the sting/hair-like projection.
CompositionComposed of novel Cnidaria-specific genes.Composed of mini-collagens and the glycoprotein NOWA.

What is a Cnidocyte?

It is an explosive cell that ejects a thread-like projection or a ting used as a defence mechanism. It consists of many organelles- cnida, cnidocnseyst, nematocyst, ptychocyst, and spirocyst.

It is a well-differentiated cell, and the response span is in milliseconds.

Whenever a predator approaches, and the trigger is activated, the organism or the animal,

the cnidocyte, reacts in a few milliseconds. It assists the nematocyst in releasing the hair-like projection/hair/sting to stun or kill the enemy, depending upon the species.

It acts as a penetrant and as a solvent and glutinous. Cnidocytes are modified epidermal interstitial cells.

Other than defending the being, it can also be used to attack for food and locomotion. It takes time for the creature to be mature enough to use the cnidocyte as a defence mechanism.

These defence mechanisms are found in the phylum Cnidaria, which constitutes sea anemones, corals, jellyfish, Portuguese man-o-war, and other hydroids and sea pens.

cnidocyte

What is a Nematocyst?

It is a subcellular structure or organelle containing extrusive filaments found in a group of unicellular eukaryotes and Cnidarians.

It is present inside the cnidocyte and helps it to eject the hair/thread projection as a penetrant, solvent, and agglutinant. When the trigger is activated, the cnidocyte makes the nematocyst release the sting/hair, called the cnidocil.

When properly stimulated, the thread is ejected and, depending on the type of nematocyst may either adhere to surrounding objects, penetrate prey or offend organisms.

It comprises mini-collagens and the glycoprotein NOWA, consisting of a globular or egg-shaped capsule.

nematocyst

Main Differences Between a Cnidocyte and Nematocyst

  1. A cnidocyte is present on the creature’s skin (on the tentacles in the case of jellyfish), whereas a nematocyst is inside the cnidocyte.
  2. A cnidocyte is like an inverted cell, whereas a nematocyst is a bag-like and globular structured subcell.
  3. A cnidocyte assists the nematocyst when triggered, whereas a nematocyst releases the cnidocil.
  4. A cnidocyte comprises cnidaria-specific genes, whereas a nematocyst comprises mini-collagens and glycoprotein NOWA, a novel protein with mini collagen Cys-rich domains.
  5. A cnidocyte consists of cnida, cnidocyst, nematocyst, ptychocyst, and spirocyst, whereas a nematocyst consists of a cell in the capsule containing thread.
Difference Between Cnidocyte and Nematocyst
References
  1. http://www.ijdb.ehu.es/web/paper.php?doi=10.1387/ijdb.113472ab
  2. https://science.sciencemag.org/content/243/4898/1589.abstract

Last Updated : 11 June, 2023

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