Question

Which cells are absent in the gastrodermis of Hydra?
(a)Gland cells
(b)Nutritive cells
(c)Stinging cells
(d)Nerve cells

Answer 1

Gastrodermis, as the name suggests, is the layer of cells that is responsible for the digestion of the food material in hydra. The gastrodermal layer is made up of various cells that take an active part in the digestive process.

Complete answer:
The cellular layer which lines the alimentary canal in Hydra is known as the gastrodermis. In the inner gastrodermis layer of Hydra, nutritive muscular cells, gland cells, nerve cells, sensory cells, and interstitial cells are present. Stinging cells or nematocysts are absent.

Additional Information: Hydra is a solitary polyp found in the freshwater. Hydra is known as one of the smallest polyps found in the marine environment and is a carnivore in its feeding habits. Hydra is diploblastic and has a tissue grade of organization with the division of labor. Hydra has a cylindrical body with 6 to 10 tentacles present. These are hollow tentacles that help in locomotion and food capture. The body wall of Hydra gas ectoderm and encoder, in between a very thin delicate mesogloea is present. Ectoderm contains epithelio-muscular cells, sensory cells, nerve cells, interstitial cells, and stinging cells or nematocysts.
So, the correct answer is ‘stinging cells’.

Note: Linnaeus gave the name Hydra, a Greek word that means water serpent on the basis of its ability to regenerate its lost parts. Hydra has great regeneration capacities. It is found that a piece of hydra will regenerate into a full hydra given it contains a part of epidermis and gastrodermis and size isn’t less than $\dfrac{1}{6}$ mm in diameter.