Question

Describe briefly how Hydra digests food and removes waste from itself.

Answer 1

Digestion in Hydra

Hydra is a smaller fresh water organism belongs to phylum Cnidaria and class Hydrozoa.

Hydra is carnivorous and feeds mainly on small crustaceans. They have special type of cells on their body called Tentacles which helps them to catch the prey. Tentacles consist of different type of stinging cells called Nematocysts. Hydra catch the prey by tentacles and paralyse it by releasing toxin which is released by spines present on tentacles.

The tentacles pull the food towards the mouth and then to digestive cavity or gastrovascular cavity. Enzymes are secreated from bordering cells of cavity on the food for extracellular digestion which digest the food and smaller particles of food are engulfed by the cells of lining of digestive cavity and by vacoules ( for intracellular digestion ).

Excretion in Hydra

Hydra has no specialized excretory organ. Hence, excretion occurs through general body surface.

Hydra is ammonotelic ( Nitrogenous waste are ammonia based ) and waste is removed by diffusion through body surface.

Some of the waste is sometimes stored in a gastrodermis, which are excreted through body surface by pore.