Mollusca and its economic importance.

Definition of the Mollusca:

The term mollusca was first applied by Aristotle to the cattle fish of the Aegean Sea. It is derived from Latin word Mollis or molluscs which mean soft bodies.This includes the claim, snails, slugs, octopods, squids, and nautili which are bilaterally symmetrical triploblastic, animals with anus and coelom and without segmentation. There are about 80,000 living species are known in this phylum.They usually have the shell and a characteristics ventral muscular foot.In Latin, molluscs are the name of the soft nut with a thin shell, referring to the bivalve shell and the soft-bodied animal within the shell. The term mollusca are the most abduent of all animals. In numbers of species, the mollusca is the second largest phylum after arthropods. Mollusca has no uniform plan as well as no specific shape. Most of them are slow moving and confined to rather special habitats. In the evoluntary sense, they are plastic materials as the outlines of the body are freely altered as new habitats are acquired and new structure are needed.

Economic importance of Mollusca:

Molluscs are of major interest to man .About 10,000 species are of economic importance. Mostly they are beneficial to man and some are indirectly harmful. Some of the beneficial mollusca are used for-

1. [BeneficialMollusca];Most of the mollusca are beneficial for man which are describe below.

1. As food.
2. As bait.
3. As ornament.
4. As money.
5. To form dye and ink.
6. Buttons and pears.
7. In art and medicine.
8. In literature.
9. Animal inventions.

A Little description about why this point is important is described below.

1. As food:

Most of the Mollusca species are eaten as food by people. Fore,g Chitons are eaten as main food of Red Indians. The gastropods are consumed by the numerous predictor chiefly fish, birds, and mammals. Mytilus edulis is used in chowder, and adductor muscle of pectin are served in flour and dried. Pelecypods also furnish food for starfish, boring sponges, drilling snails, some marine leeches, fish and shore birds.Other bivalves, octopus and cuttlefishes furnish the large quantity of a roof in Europe. Million of mounds are regarded as a delicacy some of them are clams,oysters, scallops and mussels are eaten in China, Japan, Malaya, Europe, and America.

2. As bait:

Many gastropods are very useful to man, as bait for catching fish. Squids make an excellent bait for marine fishes . Small Octopus are used as bait by the line fisherman of Palk Bay.

3. Money:

Red Indian tribes of America used the common Dentalium indianorum,as money or sawampum for various native races.Some of the Mollusca are commercially cultivated and harvested from which a large amount of money is earned by selling them. Squids, cuttlefish and devil fish earn money as they are sold in the market for food in China, Japan, India and Italy.

4. Ornament:

Nautilus shell is much used for decoration , art and for many other useful purposes. Dentalium tooth is used as an ornament. Gastropods shells are used as an ornament. some Mollusca and their parts are used as ornaments by a human. Gastropods shell are also used in forming tools. Calcareous shells of some marine snails are sought as curious.

5. To form dye and ink:

Some of the Mollusca secrets the coloured substance acting as a dye. Ink sac of cattle fish has the rich brown pigment called 'sepia' which is used by artists. Nowadays a certain brown fish of photograph is termed as a sepia finish.

6. Button and pearls:

Gastropoda shells are also used to manufacture buttons and their articles. Shells of certain bivalves have been used for mother of pearl layer also for buttons, knife handles.Pearls are made by the clam and pearl oysters themselves and are among the most beautiful and valuable of our jewels.

7. In art and medicine:

Some Mollusca shells are used as art and medicine, for eg, internal calcareous shell of Sepia " the cattle bone" is used as medicine as well as for the other purposes.

8. In literature:

Giant Squids and octopus are used as the major character in various stories ; so that they have literature valve also.

9. Animal inventions:

These methods used by Mollusca as formed millions of years ago later invented by human and are used for mankind. Cephalopods get the credit for two inventions. One is the "Jet propulsion" and another is the "smoke screen".

II [Harmful Mollusca]

In spite of some beneficial valve of the Mollusca, some of the Mollusca are harmful too.Some of the destructive activities of some mollusca are of great important to the global economy. Some of them are:

1. Herbivores.

Some of the herbivorous gastropods like slug and snails damage garden plants, vegetables, mushroom bed and other wooden structures.

2. Carnivores.

Some carnivorous Mollusca causes destructive by preying. Giant squid engages in battle with whale causing their tongue injured. Some carnivorous Mollusca can cause destructive by preying.

3. Parasites.

Some gastropods also bear a parasites life. Gastropoda acts as ectoparasitic life in echinoderms. Some act as the endoparasites of a stomach.

4. Intermediate hosts:

Some snails act as intermediate hosts for various harmful parasitic flatworms, such as Fasciola, Schistosoma.

6. Commensal:

Some pelecypods bear the commensalism.Polychaetes, Mediolaria in the test of a sea- squirts and Vulsella in sponges.

Reference:

Aggarwal Sarita. A Text Book of Biology,New Delhi.: Madhuban Educational Books, 2011.

Bhamrah, H.S., and Kavita, Juneja. A Text Book of Invertebrates, New Delhi: Anmol Publications Pvt Ltd, 2011.

Jordan E.L. and P. S., Verma. Invertebrate Zoology, New Delhi,: S. Chand and Company Pvt. Ltd., 2011.

Kotpal, R. L.,Modern Text Book of Zoology: Invertebrates, New Delhi, India: Rastogi Publications,2011.