Body Wall and Nematocysts
Cnidarians are diploblastic organisms that have different layers of tissue, the tissue is made up of cells that perform specific functions. The tissue of Cnidarians are organized into two embryological layers. These layers are the epidermis, gastrodermis, and mesolgea. The tissue is organized with the epidermis as the outer layer, the gastrodermis is the inner layer, and the mesoglea is inbetween both the epidermis and gastrodermis.
The epidermis and gastrodermis have specialized cells that help in protection, gathering food, coordination, movement, digestion, and absorption. Cnidocytes are cells that produce structures called cnidae, and can be in the gasrodermis or epidermis. Cnidae are used for attachment, defense, and feeding. An intracellular capsule filled with fluid and is enclosing a coiled hallow tube is called a Cnida (organelles). The cnida is closed at one end by a operculum cap, most cnidarians have more than 6 types of cnidae and there are 30 different types of cnidae. Cnidocytes also have a modified cilium called a cnidocil. When the cnidocil is stimulated the operculum may open. Nematocysts are a type of cnida. Nematocysts gather food and release a tube with spines to attack its prey in order to defend itself. The spines are able to release toxins that may paralyze its prey. There are other types of cnidae besides nematocyst that defend themselves in different ways. For example, instead of having a tube with toxins, the cnida might anchor itself to it's prey by wrapping it's tube around them.