Question

Nematocysts are found in animals belonging to phylum.
A. Coelenterata
B. Chordata
C. Mammalia
D. Reptilia

Answer 1

Nematocysts are also known as cnidocyst. Its defense mechanisms present some organisms that help them attack their prey. There are venomous cells present in the bodies of these organisms.

Complete answer:
-Nematocyst is a minute, either spherical or elongated capsule produced by the members of the phylum Cnidaria. Several capsules occur on the surface of the body. Each is produced by a special cell called a nematoblast or cnidoblast. They contain a hollow, coiled, usually barbed thread, upon proper stimulation it quickly turns outward from the capsule. The purpose of the thread that contains poison is to capture prey or to ward off the enemies.
-When stimulated by mechanical or chemical cues, a lid-like structure which is present on top of the capsule pops aside, and this thread everts explosively with a twisting motion. As twisting and eversion proceed, the barbs act like drill, penetrating into the foreign object. If toxin is present, it passes through a hollow thread, penetrating and paralyzing the tissues of the victim. The thread separates from nematocyst after eversion. Some nematocysts threads ensnare small prey by wrapping about them. The stinging effect of nematocysts in some organisms can be painful to humans and may cause shock, paralysis and even death.
-Nematocysts are a specific feature to Coelenterates that act as organs of defense and offence. They are also called as Cnidae and hence, coelenterates are also called as Cnidarians.

Hence, the correct answer is option (A).

Note: Around 30 different types of nematocysts are present in different groups of cnidarians. Some of them are penetrants, volvents, spirocysts, ptychocysts, glutinants, stereoline glutinant, streptoline glutinants.