Stinging cells (cnidocytes or cnidoblasts or nematoblasts) are used for offence and defence. These have nematocysts (the stinging organs), composed of capsule, shaft and thread tube. The thread tube coils around the prey or attaches to it or injects a toxin, called hypnotoxin which paralyzes the victim. They are found in cnidarians- sea pen (Pennatula), sea fan (Gorgonia). etc.

Stinging Capsules or Nematocysts in Animals

Nematocysts or stinging capsules are specialized organelles found in various marine organisms, particularly in the phylum Cnidaria. Cnidarians are a group of aquatic animals that include jellyfish, sea anemones, hydroids, and corals. Nematocysts are responsible for the characteristic stinging ability of these organisms. Let's explore the details of nematocysts and their functions in Cnidaria.

Definition and Structure of Nematocysts
Nematocysts are microscopic capsules that contain a coiled, harpoon-like structure called a cnidocyst. These capsules are located in specialized cells called cnidocytes, which are present on the tentacles and other body parts of cnidarians. Each nematocyst is enclosed by a thin, elastic membrane and contains a toxin-filled tubule, which is coiled up inside the capsule.

Function of Nematocysts
Nematocysts serve various functions in Cnidaria, including:

1. Prey Capture: Cnidarians use nematocysts to capture their prey. When a suitable organism comes into contact with the tentacles of a cnidarian, the nematocysts fire rapidly, injecting toxins into the victim. This immobilizes or kills the prey, making it easier for the cnidarian to consume.

2. Defense Mechanism: Nematocysts also act as a defense mechanism for cnidarians. When threatened or disturbed, the organism releases nematocysts to deter or immobilize potential predators.

3. Attachment and Movement: Some cnidarians use nematocysts to attach themselves to surfaces or to aid in movement. For example, sea anemones use nematocysts to anchor themselves to rocks or other substrates, while jellyfish use them for propulsion.

Types of Nematocysts
There are numerous types of nematocysts found in different species of cnidarians. Some common types include:

1. Penetrant Nematocysts: These nematocysts have elongated tubules and are used to penetrate the prey's body, injecting toxins directly into its tissues.

2. Volvent Nematocysts: Volvent nematocysts have spines or threads that rapidly uncoil when they come into contact with a prey, entangling and immobilizing it.

3. Glutinant Nematocysts: Glutinant nematocysts secrete sticky substances, allowing the cnidarian to trap and immobilize its prey.

Conclusion
Nematocysts are specialized capsules found in cnidarians such as jellyfish, sea anemones, hydroids, and corals. These capsules contain a coiled tubule filled with toxins and serve various functions, including prey capture, defense, and attachment. Understanding the structure and function of nematocysts is crucial in comprehending the unique characteristics and behaviors of these fascinating marine organisms.

Stinging capsules r found in coelenterata or cnideria..

it is useful in offense nd defense..