Kingdom of seashells: Explotation and culture of major commercial species

A soft-boiled animal is present beneath this hard shell. This shell gives the protection to that animal. Marine mollusks such as; calms oysters, mussels, snails are having exoskeleton which is a hard protective covering layer. These shells are major source of organic decomposition. This layer is so hard by the presence of calcium carbonate with a very less quantity of protein. All the seashells play a very important role for ecology and our human society as well. In ancient days seashells like cowry and tusk shells are using as currency. As these are easy to carry and durable too. For making ornaments, cutting tools, lamps, basins these shells are used world widely. Even in some parts of India for astrological prediction cowries are using. Mostly decoration of seashells started by Portuguese in Goa and more over the near about coastal areas. This unique craft is now familiar in everywhere. Around 50,000 mollusk species are found on earth. Some are used as seafood or in craft industries.


Introduction
The beauty of hard outer protective layer of shells is admire by each and everyone. According to Hindu mythology some shells of Turbunaria sp.are believed to be the sacred refl ection to the God Vishnu. From the ancient days the chank is considered as holy. Seashells are found in wide range of colors, sheds, tones and texture.
A soft-boiled animal is present beneath this hard shell. This shell gives the protection to that animal. Marine mollusks such as; calms oysters, mussels, snails are having exoskeleton which is a hard protective covering layer. These shells are major source of organic decomposition. This layer is so hard by the presence of calcium carbonate with a very less quantity of protein. All the seashells play a very important role for ecology and our human society as well. In ancient days seashells like cowry and tusk shells are using as currency. As these are easy to carry and durable too. For making ornaments, cutting tools, lamps, basins these shells are used world widely. Even in some parts of India for astrological prediction cowries are using. Mostly decoration of seashells started by Portuguese in Goa and more over the near about coastal areas. This unique craft is now familiar in everywhere. Around 50,000 mollusk species are found on earth. Some are used as seafood or in craft industries.
Around 5070 numbers of species are found in India. Among them some are belong to freshwater or marine habitat. In India marine mollusk diversity is rich and abundantly found in coast of Gujarat,Tamilnadu, Andaman and Nicobar island Lakshyadeep island. Various gastropod species are found in India, which is gradually exploited due to its several uses.

Common gastropods found in India
Gatropoda is the largest molluscan class having a large diversifi cation. In larval stage it going through the process 'torsion'. In this process the entire top of their body twists 180 degree on their foot. This is coiled shpe. It maybe left-handed or right-handed. Left-handed coil is known as sinistral (spiraled counter -clockwise) and right-handed coil is known as dextral

Common bivalves found in India
Bivalves belong to the phylum mollusca. It is the largest phylum of invertebrate animals known as mollusca, secondly only to Arthropods. 'Mollusc' word originates from Latin word, derive from the word 'mollis' which means soft. This successful group of animals is found in a wide environmental range. These are highly diverse found in terrestrial, marine and freshwater habitats. Among them freshwater mussels are coming under class Bivalvia which comprises about 14% of total molluscan species. The organisms like clams, mussels, Here the role of mantel is very vital as bioaccumulation of metal and organic contaminants in addition to gills, kidney and digestive glands. Mussels are also treating as excellent indicators of the long term health of aquatic ecosystem. In adverse condition adult mussels cannot respond quickly as they are sluggish in nature and if they disappear from a area then slowly they can recolonize. In adverse environmental condition their growth rate become very slow, either they die or stop reproducing. The stress factors like low dissolved oxygen, chemical contamination and sedimentation are affecting the growth of mussels. When the contaminants such as mercury, lead, dioxin, poly-chlorinated biphenyls, and aromatic hydrocarbons are present in tissue, then it will indicate the exposure risk of entire aquatic community and the ecosystem health. Excessive suspension of sediments affects the mussels because it clogs the gills which interfere both feeding as well as respiration. Therefore, as a biofi lter mussel could be used in the early stages of drinking water treatment. marabarica). Ban of fi shing season and regulation act on mesh size is there to avoid exploitation .Localized overexploitation of stock is a major drawback in bivalve fi sheries. Due to lack of proper data base of bivalve landing is creating obstacles for researchers to conclude population of particular species.

Use of seashells
Freshwater mussels are important in aquatic ecosystem because they are sedentary suspension feeder so that they can remove a variety of materials from the water column including sediments, organic matters, bacteria and phytoplankton. In short term it can be say that mussels are biofi lters or living fi lters. To remove the suspended matters from drinking water is considered as desirable in order to treatment of the water and reducing algal bloom. British rivers indicate that mussel fi ltering removes between 7% and 30% of the particulate, after in a parcel of water travelling 10 km downstream. This implies that mussels play an important role in the removal of suspended particulate matter in river ecosystem (McIvor, 2004).
Some part of India molluscan sp. is using as food in their diet. Few molluscan sp are sold in regional market daily.
The shell of bivalves has quantifi ed uses in pharmaceutical, lime, dye industries. Bivalve is a combination of biomaterials. It accounts more calcium carbonate and minerals along with small amount of other elements like; nitrogen, sulfur, phosphorus, potassium and magnesium. This is the reason the bivalve shell is the potential source of lime for use in water treatment. This lime is being used for white washing, tobacco products, cement, bleaching powder, jagerry industries and country liquor distillation units (Naidu and Mishra 1998; Pattanayak and Mishra 2004; Panda and Mishra, 2007) [3,4].
In aquatic food chain bivalves are having a remarkable position. The fl esh of the mussel is used as feed ingredient for carnivorous fi shes and prawn culture as it is rich in protein and other nutrients.
From the archaeological excavation it has been seen that people were using the bivalves shells to temper pottery, utensils and for the making of sharp tools. Even now-a-day in some part of Odisha the tribal community uses sharpened shells as peeler. North American people making fi shing tools, plow blades and hoes for tilling the soil, shovels.
Shell decoration is a distinctive form of decoration. This is easy to handle and this craft is so popular in both rural and urban area. Now it's a trend for decoration material in aquarium. For oil lamp or pen stand it used to use.

Conservation of seashells
According to IUCN, 2016; only 87 of 283 critically endangered terrestrial gastropods found worldwide. Habitat loss, perturbation, invasive species and pollution may increase the impact of climate change in many species. Some ornamental molluscs has been declared as endangered. Those endangered species are protected and coming under Wildlife Protection Act [5][6][7][8].

Conclusion
Now-a-days tourism is interesting hobby and very frequency is for beach areas. Shell collecting avocation is popular all worldwide, for them protection is essential because they are getting over-exploited. Human activity, climate change issues need to take concern for their conservation and balancing the ecology. For biodiversity restoration these benthic organisms are keystones. Some survey has been shown that number of seashells is getting reduce by three fold within ten years. Shells have multiple functions in natural ecosystem so their conservation and protection is essential. Outer hard sea shells provide building material for birds, attachment surface t many marine organisms like, sponges, algae. Some animals like hermit crab take shelter in that exoskeleton which can protect it from predators also. Bivalves are the natural bio-fi lter which can out the pollutants from the water. The conservation of these biotic components are necessary not just for aesthetic reason but for their vital role in ecosystem. These are important for economic as well as ecological resources.