Human interaction Mollusca

1 human interaction

1.1 uses humans

1.1.1 bioindicators


1.2 harmful humans

1.2.1 stings , bites
1.2.2 disease vectors
1.2.3 pests

human interaction

for millennia, molluscs have been source of food humans, important luxury goods, notably pearls, mother of pearl, tyrian purple dye, sea silk, , chemical compounds. shells have been used form of currency in preindustrial societies. number of species of molluscs can bite or sting humans, , have become agricultural pests.

uses humans

molluscs, bivalves such clams , mussels, have been important food source since @ least advent of anatomically modern humans, , has resulted in overfishing. other commonly eaten molluscs include octopuses , squids, whelks, oysters, , scallops. in 2005, china accounted 80% of global mollusc catch, netting 11,000,000 tonnes (11,000,000 long tons; 12,000,000 short tons). within europe, france remained industry leader. countries regulate importation , handling of molluscs , other seafood, minimize poison risk toxins can accumulate in animals.

saltwater pearl oyster farm in seram, indonesia

most molluscs shells can produce pearls, pearls of bivalves , gastropods, shells lined nacre, valuable. best natural pearls produced marine pearl oysters, pinctada margaritifera , pinctada mertensi, live in tropical , subtropical waters of pacific ocean. natural pearls form when small foreign object gets stuck between mantle , shell.

the 2 methods of culturing pearls insert either seeds or beads oysters. seed method uses grains of ground shell freshwater mussels, , overharvesting purpose has endangered several freshwater mussel species in southeastern united states. pearl industry important in areas, significant sums of money spent on monitoring health of farmed molluscs.

byzantine emperor justinian clad in tyrian purple , wearing numerous pearls

other luxury , high-status products made molluscs. tyrian purple, made ink glands of murex shells, ... fetched weight in silver in fourth century bc, according theopompus. discovery of large numbers of murex shells on crete suggests minoans may have pioneered extraction of imperial purple during middle minoan period in 20th–18th centuries bc, centuries before tyrians. sea silk fine, rare, , valuable fabric produced long silky threads (byssus) secreted several bivalve molluscs, particularly pinna nobilis, attach sea bed. procopius, writing on persian wars circa 550 ce, stated 5 hereditary satraps (governors) of armenia received insignia roman emperor given chlamys (or cloaks) made lana pinna. apparently, ruling classes allowed wear these chlamys.

mollusc shells, including of cowries, used kind of money (shell money) in several preindustrial societies. however, these currencies differed in important ways standardized government-backed , -controlled money familiar industrial societies. shell currencies not used commercial transactions, social status displays @ important occasions, such weddings. when used commercial transactions, functioned commodity money, tradable commodity value differed place place, result of difficulties in transport, , vulnerable incurable inflation if more efficient transport or goldrush behavior appeared.

bioindicators

bivalve molluscs used bioindicators monitor health of aquatic environments in both fresh water , marine environments. population status or structure, physiology, behaviour or level of contamination elements or compounds can indicate state of contamination status of ecosystem. particularly useful since sessile representative of environment sampled or placed. potamopyrgus antipodarum used water treatment plants test estrogen-mimicking pollutants industrial agriculture.

harmful humans
stings , bites

the blue-ringed octopus s rings warning signal; octopus alarmed, , bite can kill.

some molluscs sting or bite, deaths mollusc venoms total less 10% of jellyfish stings.

all octopuses venomous, few species pose significant threat humans. blue-ringed octopuses in genus hapalochlaena, live around australia , new guinea, bite humans if severely provoked, venom kills 25% of human victims. tropical species, octopus apollyon, causes severe inflammation can last on month if treated correctly, , bite of octopus rubescens can cause necrosis lasts longer 1 month if untreated, , headaches , weakness persisting week if treated.

live cone snails can dangerous shell collectors, useful neurology researchers.

all species of cone snails venomous , can sting painfully when handled, although many species small pose of risk humans, , few fatalities have been reliably reported. venom complex mixture of toxins, fast-acting , others slower deadlier. effects of individual cone-shell toxins on victims nervous systems precise useful tools research in neurology, , small size of molecules makes easy synthesize them.

disease vectors

skin vesicles created penetration of schistosoma. (source: cdc)

schistosomiasis (also known bilharzia, bilharziosis or snail fever), disease caused fluke worm schistosoma, second malaria devastating parasitic disease in tropical countries. estimated 200 million people in 74 countries infected disease – 100 million in africa alone. parasite has 13 known species, 2 of infect humans. parasite not mollusc, species have freshwater snails intermediate hosts.

pests

some species of molluscs, particularly snails , slugs, can serious crop pests, , when introduced new environments, can unbalance local ecosystems. 1 such pest, giant african snail achatina fulica, has been introduced many parts of asia, many islands in indian ocean , pacific ocean. in 1990s, species reached west indies. attempts control introducing predatory snail euglandina rosea proved disastrous, predator ignored achatina fulica , went on extirpate several native snail species, instead.