What is the bell like shape of a cnidarian called?
In biology, a medusa (plural: medusae) is a form of cnidarian in which the body is shaped like an umbrella. The other main body-form is the polyp. Medusae vary from bell-shaped to the shape of a thin disk, scarcely convex above and only slightly concave below.
What is a cnidarian body plan called?
Cnidarians have two distinct body plans, the medusa (a) and the polyp (b). All cnidarians have two membrane layers, with a jelly-like mesoglea between them. Animals in this phylum display two distinct morphological body plans: polyp or “stalk” and medusa or “bell” (Figure 2).
What are the two types of cnidarian body plans?
There are two basic cnidarian body shapes: a polyp form, which is attached to a surface; and an upside-down free-floating form called a medusa. Some cnidarians change form at different phases of their life cycle, while others remain in one form for their entire life.
Where on the body of a cnidarian are these structures located?
These cells are located around the mouth and on the tentacles, and serve to capture prey or repel predators. Cnidocytes have large stinging organelles called nematocysts, which usually contain barbs at the base of a long coiled thread.
What is Nematocyst 9th std?
Nematocysts are organelles that have stinging cells. They are present in Cnidarians. Nematocyst paralyses the preys by injecting poison and helps Cnidarians to catch their prey.
What is the main function of nematocysts?
Nematocysts or cnidocysts represent the common feature of all cnidarians. They are large organelles produced from the Golgi apparatus as a secretory product within a specialized cell, the nematocyte or cnidocyte. Nematocysts are predominantly used for prey capture and defense, but also for locomotion.
What are two functions of Cnidocytes?
Cnidae are used to capture prey and as a defense against predators. A cnidocyte fires a structure that contains a toxin within the cnidocyst; this is responsible for the stings delivered by a cnidarian.
What is Nematocyst in zoology?
Nematocyst, minute, elongated, or spherical capsule produced exclusively by members of the phylum Cnidaria (e.g., jellyfish, corals, sea anemones). Several such capsules occur on the body surface.
Is a Nematocyst a cell?
Nematocyst (noun, “knee-MAH-tah-sist”) This is a special cell found in some ocean critters — such as jellyfish, sea anemones and corals — that has a stinging barb coated in venom. Before the nematocyst fires, its barb stays coiled inside the cell in a chamber where it is bathed in venom.
How does a Nematocyst work?
A nematocyst is a specialized organelle found in all cnidarians. When it is triggered to discharge, the extremely high osmotic pressure within the nematocyst (140 atmospheres) causes water to rush into the capsule, increasing the hydrostatic pressure and expelling the thread with great force.
What triggers a Nematocyst to activate?
The cell’s thread is coiled under pressure and wrapped around a stinging barb. When potential prey makes contact with the tentacles of a polyp, the nematocyst cell is stimulated.
What is inside a Nematocyst?
Inside the nematocyst is a thread-like, coiled, hollow tube with toxic barbs. This tube is everted from the capsule to deliver a paralyzing sting to the target prey or enemies. Thus, nematocysts are chiefly for food gathering and defense mechanism of Cnidarians.