Economic Importance of Mollusca
Introduction:
Molluscs are of general importance within food chains and as members of ecosystems.
Many gastropods, bivalves, and cephalopods are a source of food for many cultures and therefore play an important role in the fishing industries of many countries.
In addition to their economic value as food, mollusks are also used to make jewelry the most notable and valuable example of which is pearl jewelry.
While clams, oysters, snails and squid frequently contribute to many coastal
economies as food sources, the shells of various mollusks have also been used as a form of currency at times throughout history.
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Molluscs are of great important in various ways:
Certain species are of direct or indirect commercial and even medical importance to humans.
Many gastropod species, for example, are necessary intermediate hosts for parasitic flatworms (class Trematoda, phylum Platyhelminthes), such as the species that cause schistosomiasis in humans.
Most bivalves contribute to the organic turnover in the intertidal (littoral) zones of marine and fresh water because, as filter feeders, they filter up to 40 litres (10 gallons) of water per hour.
This filtering activity, however, may also seriously interfere with the various populations of invertebrate larvae (plankton) found suspended and free-swimming in the water.
One species, the zebra mussel (Dreissena polymorpha), is regarded as a particularly harmful exotic invader.
Carried from Europe in ship ballast water, zebra mussels were taken to the Great Lakes in 1986.
To date, they have caused millions of dollars in commercial damage by clogging the water pipes of power plants and cooling systems.
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Harmful Molluscs:
Molluscs are indirectly harmful to man but most of them are beneficial.
The harmful molluscs are slugs and shipworms.
Slugs are injurious in gardens and cultivations. They not only eat leaves but also destroy plants by cutting up their roots and stems.
Teredo, a shipworm damages wooden parts of ship.
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Great source of food:
Many mollusks are great source of food for man in many parts of world.
China is a leader in the worldwide mollusk catch and reached an 80 percent global share in 2010.
France is the industry leader in the European catch.
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Pearl Industry:
The pearl industry has become a vital part of some countries economies, and significant sums of money are allocated to the monitoring of the health of mollusks produced on farms.
Large quantity of calms, oysters and mussels are eaten in Fareast, Europe and America.
Oysters are regarded as delicacy.
Shell of fresh water mussels is used in button industry.
The shell of oyster are mixed with tar for making roads in America.
Shells in certain parts of world are also used for making ornaments. Some oysters also
make valuable pearls e.g. the pearl oyster. Some pearls are used for making jewellery. Some
animals including in this phyla are use to eat in some countries. Their shell are also used in art and craft industries.
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Benefits of Molluscs :
1.Many molluscs including mussels, oysters, clams and cephalopods are fished for food and support small scale sustenance fisheries in developing countries.
Various species in this phylum are very important to the human beings. Clams and Mussels are an important food source in different parts of the world.
Octopuses, squids, whelks, oysters and scallops are also eaten by the human beings.
They form an important part of the fisheries and agricultural industry.
2.Oysters are nutritious as they contain vitamin A and B, minerals and appreciable amount of glycogen and protein.
3.Pearl oyster produces pearl, considered a highly valuable jewel, within its shell. Most precious pearls are found in pearl oysters of the genus Pinctada.
4.Chank fishery, a great source of revenue in India is based on a turbinellid gastropod, Xanus pyrum, the shell of which is called the "chank". Chanks are used as trumphet in temples and in the manufacture of bangles.
5.Thick shells having lustrous pearly layer are valued high in the manufacture of buttons, brooches and the like objects.
6.The shells of Cymbium, Dolium, Murex, etc are made into useful articles like lamp stands, lamp shades, etc.
7.Tools, utensils and objects of delight have been formed from gastropodan shells.
8.Nautilus shell is much used for decoration, art and for many other useful purposes.
9.Many shells go into the making of toys, some are polished and sold as curios like the calcareous operculum of turban shells.
10.Dead shells drifted ashore at estuaries by currents, sub-fossil deposits in lakes and broken shells of surf beaten beaches, form the raw material for superior quality lime, which is used in every type of masonry constructions and in whitewashing the buildings.
11.Good quantities of shells are used in carbide and cement manufacture.
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12.Many gastropods like squids and small octopus are used as bait for catching fish.
13.Gastropodan shells were used as source of money by various native races as Red Indian tribes of America used the common Dendallium as money.
14.Some gastropods like Nucella and Murex, are sources of Tyrian purple, a dye obtained from their juices. Ink sac of cuttle-fish provides a rich brown pigment called "sepia", used by artists.
15.Fossil cephalopods have a medicinal importance among the red Indians of Montana and Wyoming. They collect the preserved fossil ammonoids and keep them as "medicine".
16.The credit of "jet propulsion", only recently discovered by man, goes to cephalopods, who have been using it for millions of years.
17.Some gastropods like land slugs and snails cause damage to gardens, orchards, green houses and mushroom beds by feeding upon the succulent parts of seedlings and mature plants.
18.The shipworm, Teredo, a bivalve mollusc bores in wooden boats and ships, causing millions of dollars of damage to wooden structures.
19.Some gastropods cause damage to other molluscs like the marine snail Urossalprinx, causes serious loses to oyster industry by drilling the oyster shells.
20.Some predacious and carnivorous molluscs cause distruction to fishery industry.
21.Snails have importance from a medical point of view as they serve as intermediate host for flatworms, like Fasciola and Schistosoma.
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Medicinal Importance:
1.The deadly venoms of some Cone Shells (Conidae) are today being used to help victims of strokes and heart disease, and to produce a revolutionary new drug for chronic pain control.
2.An extract from the hard clam or "Quahog" (Mercenaria mercenaria L.) is a strong growth inhibitor of cancers in mice. It is called mercenine, after the clam's scientific name.
3.Paolin, a drug made from abalone juice, is an effective inhibitor of penicillin- resistant strains of bacteria.
4.Ground and processed oyster shells Olympia Oyster (Ostrea conchaphila) are used as a calcium supplements both for humans and animals.
5.Oyster juice has been found to have anti-viral properties, and may be made into a drug eventually.
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6.The threads that some mussels (Mytilidae) use to attach themselves to rocks, piers, and other hard surfaces are being tested as possible glue in surgery. These are called "byssal" threads, from the Latin word byssus, which means "fine linen", which is silky, like the fine threads of many mollusks (Mytilus edulis)
7.The cement of the Carrier Shells (Xenophoridae) is being studied for use as a possible cement for bone fractures.
The Carrier shells are the camouflage experts of the mollusc world: they attach all kinds of objects - shells, rocks, pieces of coral, sponges, bottle caps. to their shells, so they look like a little pile of trash on the bottom of the sea - a great way to avoid being eaten.
8.In Vietnam, traditional medicine has a wide variety of uses for shells: powdered oyster shell is taken to treat acid indigestion, fatigue and to stop hemorrhage.
It is also sprinkled over open wounds and boils.
Cuttlefish bones are used as a remedy for rickets (which is caused by lack of vitamin C), a healing agent in the treatment of gastro-intestinal troubles, a local anti-hemorrhagic (i.e., it stops internal bleeding), and as an antiseptic is cases of inflammation of the middle ear.
The flat shell of the Abalone, with its iridescent inside, is powdered and taken orally to improve vision, to remove keratoses (cataracts), and to improve such conditions as hemeralopia (where you can see at night well, but hardly at all in the daytime!.
Powdered pearls from oysters are used as a topical eye medicine and it has been scientifically proven to have some anti-inflammatory effects on a painful condition called conjunctivitis, where the surface of the eye becomes red and sore.
9.Slugs and snails are terrestrial molluscs which have similar morphology except that slugs, unlike snails, have no obvious shell, although some species possess a partial or internal vestigial shell.
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Widely distributed around the world, the largest species of slug in the UK, the Ashy-Grey slug (Limax cinereoniger), can exceed 25 cm in length. For centuries snails, and to a lesser extent slugs, have been used both as a food and as a treatment for a variety of medical conditions.
In some part of Italy, the common garden slug, Arion hortensis, is sometimes swallowed whole as a treatment for gastritis or stomach ulcers.
In America slugs are not thought to be swallowed live in this way, but a recipe for "Slug Syrup" made up of with sugar be used for the treatment of ulcers, bronchitis and asthma.
Snail and slug slime have been used sporadically as skin treatments since the time of the Ancient Greeks.
It has recommended that the use of crushed snails to relieve inflamed skin and some 20 years ago, the potential of snail slime was noted by Chilean snail (Elicina) farmers who found that skin lesions healed quickly, with no scars, when they handled snails for the French food market.
Snail Cream with 70% snail extract "soothes regenerates and heals skin".
Snail slime based products are claimed to be the new miracle face-fixer in the U.S where they are used to treat acne, reduce pigmentation and scarring, and combat wrinkles.
It has also been reported slugs are used in Italy to treat dermatological conditions.
Mucus collected from a slug is rubbed onto the skin to treat dermatitis, inflammations, calluses, and acne, and to promote wound healing.
In addition, in a special ritual slugs themselves are used for the treatment of warts.
Mucus from a live slug is first rubbed onto the wart, and then the slug is hung out in the sunshine to dry out and die.
It is believed that once the slug has dried up, the wart should as well.
The use of slugs for the treatment of warts is not, however, confined to Italy.
Records exist of the use of slug slime in the US and UK some of which recommended that the slime be collected at certain phases of the moon to ensure maximum effect.
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1.Invertebrate Zoology- By E. L. Jordan and P.S. Verma
2.Modern Text Book of Zoology: Invertebrates- By R.L. Kotpal
3. A Text Book of Invertebrates- By H.H. Bhamrah and J. Kavita
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