Question

Poisonous fluid present in nematocysts of Hydra is
A. Hypnotoxin
B. Haematin
C. Haemozoin
D. Agglutinogen

Answer 1

Hint: Hydra is a freshwater organism of phylum Cnidaria and class hydrozoa. It is an invertebrate. Hydra has a tubular body. The mouth opening of Hydra is surrounded by many tentacles which help the animal in moving and gathering food for itself.

Complete Answer:
Nematocysts of Hydra:
- Nematocysts are also called the Cnidae that’s why Coelenterates like Hydra are called Cnidarians.
- Nematocysts are stinging cells that are the organs of offense and defense.
- Nematocysts are produced by the cells called Nematoblasts.

Structure of Nematocysts:
- Nematocysts are the cell organelles that are found in a type of cell that is called cnidocytes or cnidoblasts.
- Cnidoblast is an oval or rounded cell having a nucleus lying on the basal side.
- Inside the cnidoblast there is an oval sac which is filled by the poisonous fluid called hypnotoxin (mixture of proteins and phenols).
- The outer end of the capsule is invaginated into a long, hollow and tubular threads tube.
- The base of thread is swollen to the but and contains three large spines called – barbs or stylets and three spiral rows of minute spines.
- The bladder is covered on the top by an operculum (lid) Near the bladder there is a hair-like process called a cnidocil that acts like a trigger for discharge of the thread tube.
- Nematocysts may occur scattered throughout the body surface of an organism except at the basal disc.
- Therefore, it is clear from the above discussion that the poisonous fluid present in nematocysts of Hydra is Hypnotoxin.

Hence, option A is the right answer for this question.

Note: Nematocysts are present abundantly in tentacles and hypostomes. On the tentacles nematocysts form a ‘battery of nematocysts’ which help in paralyzing the prey. This battery of nematocysts consist of two central large nematocysts which are surrounded by the 10-12 smaller nematocysts.