Question

Hydra are small simple freshwater animals. They do not have a recognizable brain or true muscles. Nerve fibres are in the form of a network. The type of neurons possessed by Hydra is
A. Apolar
B. Bipolar
C. Unipolar
D. Multipolar

Answer 1

This type of neuron is immature embryonic nerve cells that do not have any axons and dendrites. This neuron contains only one protoplasmic process that extends from the cell body.

Complete answer:
Hydra is a genus of invertebrate that belongs to the class Hydrozoa. The body of this organism comprises a thin, normally translucent tube which is about 30 mm long but can contract very high. The body wall is made up of two cell layers, separated from each other by a thin, non- structural layer of connective tissue, namely the mesoglea and the enteron. The bottom end of the body is locked and at the top ends opening intakes both foods as well as waste. A circle of 4 to around 25 tentacles is around this opening. The genus is represented by some 25 different species, especially in colour, length and number of tentacles and location and size of gonads. All Hydra species feed on small animals including crustaceans.

In contrast to other derivative animal nervous systems the nervous system of Hydra is a nerve net. Hydra has no true brain or musculoskeletal recognition. The nerve nets bind sensory photoreceptors and sensitive neurons in the wall of the body. The nervous system consists of apolar nerve cells. They are linked and distributed in a network across their entire body. This nerve cell system binds sensory photoreceptors and touches sensitive nervous cells that aid in environmental change in the tentacles.

Thus, the correct answer is option A. i.e., Apolar.

Note: Hydra has a tubular, radially symmetrical body with a length up to 10 mm and a basic adhesive foot called the basal disc. A sticky fluid is secreted by gland cells in the basal disc. There is a mouth at the free end of the body, with one to twelve small, moving tentacles around it. Every tentacle or cnida is covered in customary cells called cnidocytes, which are highly specialized in stinging cells.