Give the economic importance of sponges?

Answer 1

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1) As food: Sponges are generally unpalatable due to their unpleasant taste and odour and prickly nature of their spicules. However some crustaceans parasitize them while nudibranchs depend upon them for their regular diet.

2) As commensals: Being unpalatable the Sponges serve as secure houses for several crustaceans, worms, mollusks small fishes, etc, which seek protection in them against predaceous fishes and other enemies. In addition these animals get a rich food supply from the water circulating into the Sponge. Some animals even spend their entire life in these 'charitable hotels', providing free protection and food. Since these small creatures do not cause apparent harm to the Sponge, they are considered commensals.

Sponges themselves may be commensals. Certain species of crabs deliberately pick up and attach bits of Sponges to their back and legs. As the Sponges grow they provide a protective covering to the crabs which become well camouflaged and eventually concealed completely.

3) Other uses: The ancient Greeks used dried, fibrous skeletons of Sponges for the purpose of bathing, washing, scrubbing floor and padding shields and armour. The Romans used them for painting and moping. Some even used them to absorb fluids to be drunk later on. Though synthetic Sponges are replacing the natural ones, due to the durability, elasticity and absorbing capacity the natural ones are still preferred for washing and polishing. Sponges of inferior quality are used for stuffing the sound absorbing walls, garments, saddles, cushions, furnitures etc. and also as a packing material. In glass manufacture Sponges are used in wiping and cleaning hot glass.