ECONOMIC IMPORTANCE OF ARTHROPODS

Economic importance of arthropod
An arthropod

The arthropods comprise the largest phylum in the animal kingdom, surpassing in number of species all the other phyla combined. They may be said to be the dominant animals on the earth at the present time, if numbers of different species and numbers of individuals are accepted as criteria of dominance. To the phylum belong the lobsters, crabs, water fleas,’ barnacles, millipedes, centipedes, scorpions, spiders, mites, and insects.

Read: ADVANTAGES OF CUTICLE IN ARTHROPODS

The most important characteristic common to all of these is the possession of jointed appendages. They are bilaterally symmetrical; consist of a linear series of segments, on all or some of which is a pair of appendages; are covered with a chitinous exoskeleton which is flexible at intervals to provide movable joints; possess a nervous system of the annelid type; have a coelom which is small in the adult, the body cavity being a haemocoel filled with blood and are free from cilia.

 Importance of arthropoda groups

Merostoma

  • American species (Limulus polyphemus) sometimes fed to chickens and pigs.
  • It fattens both fowls and pigs but also imparts a shocking flavor to their flesh.
  • Asian species of horse-shoe crabs are consumed by humans.

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Arachnida

  • In tropical countries, scorpions enter houses and become nuisance.
  • Scorpions are venomous with painful sting which sometimes is fatal to children.
  • Scorpions are beneficial to some extent as they control cockroaches and beetles by feeding on them.
  • Scorpion venom is used for pharmacological, biological, biochemical and immunological researches e.g. in India.
  • Certain mite e.g. blister mite, eriophyee cause damage to crops like apple, pear, grapes, etc.
  • Ticks sucks blood of man and animals by acting as vector of protozoa causing Texas fever in cattle and tick fever in man.

Crustacean

  • Lobsters, shrimps, prawns, squillae, crayfishes, crabs form an important diet of man with great nutritive value
  • Blue crab, callinectes is held captive until it molts, then sold in soft-shelled condition and after removal of the viscera the whole animal is cooked and eaten.
  • Prawn fishery is very much advanced in several countries, giving employment to thousands.
  • Smaller species e.g Dophnia and Cyclops form bulk of zooplankton playing a vital role in food chains of both marine and freshwater fishes and aquatic animals
  • Whales too depend on crustaceans for food.
  • Aphipods and euphausids form greater part of diet of other animals (seals, seagulls and penguins)
  • Two tons of calanus (marine copepod, 5mm) found in stomach of blue whale
  • Eggs of Artemia and Daphnia are sold as fish food.
  • In most parts of America, crayfishes are popular among fishermen as fish bait
  • Crayfishes are beneficial as they serve as an agency in the destruction of decaying vegetables and animal bodies in water.
  • Some crustaceans are parasites of aquatic animals but never of man and land animals.
  • Handful of them serve as intermediate hosts to certain dangerous worms of man and other vertebrates.
  • Dreaded human lung fluke, Paragonimus westermanii uses a crayfish as intermediate host.
  • Cyclops serve as intermediate host for human guinea worm, Drancuculus medinensi and for broad tapeworm, Diphyllobothrium
  • Crayfish damage cultivated crops by eting young corn and cotton plants.
  • Sow bugs also feed on vegetation, turn pests in green houses and fields when numerous
  • Crayfishes occasionally burrow, making holes in dams and weaken them causing serious damage.
  • Some crustaceans bore into marine timber structures and destroy them causing loss of several millions.
  • Some crustacean wood borers e.g Chelura terebrans (Amphipoda) and species of spheroma and Limnoria (Isopoda) burrow into and damage wharves in salt water.
  • Barnacles form one of the fouling animals by attaching to hulls of ships.

Diplopoda

  • Millipedes are scavengers and serve to dispose dead organic matter.
  • Cause damage to plants as they feed on plant roots and destroy green houses and gardens.

Chilopoda

  • Beneficial to man as they feed on insects
  • Some have been reported to feed on snakes
  • Some are harmless to man but some tropical ones inflict painful bite and cause fever, dizziness and headache.
  • Scopelopendra gigantea causes human death if victim is a child.

Insecta

Pests of plants, fruits and stored grains

  • Insects attack leaves, stems, buds, flowers, seeds, fruits, barks, woods, roots, vegetables, stored products, wool, weathers, cigars, tools, etc.
  • Chewing insects (cabbage worm, potato beetles and hoppers) chew and swallow external parts of plants.
  • Grasshoppers and locusts have invaded green crops so long.
  • Locust move in swarms extending for many kilometers
  • Grass and leaves devoured and even broken by weight of insects settling on them.
  • Plant bugs, aphids, scale insects possess extremely sharp-pointed proboscis, thrusted into the plant tissues for sucking of the plant juices.
  • Bark beetles destroy timber in forests
  • Boil weevils spoil cotton before harvest.
  • Caterpillars and Japanese beetles strip foliage from millions of shady trees every year

Household pests

  • Several insects are unwanted guests in the house
  • Mostly annoying, sometimes they become destructive.
  • Bedbugs, mosquitoes and stable flies inflict pains and transmit diseases.
  • Ants, crickets, weevils, fruit flies and house flies contaminate food leading to spoilage.
  • Clothing, carpets, furs and feathers are damaged by cloth moths and carpet beetles.

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Injurious to domestic animals

  • Domestic animals are seriously injured by insects.
  • Many live more or less as parasites either externally (fleas, lice, bugs, mosquitoes) or internally (larvae of botfly in sheep)
  • Bird lice (Mallophaga) feeds upon feathers of chicken, causing irritation and flesh loss
  • Blood sucking horn fly is a serious pest of cattle
  • Grubs of ox warble fly cut holes in skin of cattle causing damage of hide and flesh.
  • Larvae of horse bot fly cause serious disturbances in stomach.

Disease vectors

  • Various species of Anopheles convey parasitic protozoa causing malaria.
  • Culex mosquito spread nematode worm (Wuchereria broncrofti) causing filariasis.
  • Yellow fever is spread by stegomyia.
  • Surra disease among horses, camels of tropical countries is caused by Tabanus.
  • African sleeping sickness is caused by Tse-tse fly
  • Typhoid, diarrhea, cholera are caused by Musca domestica.
  • Bubonic plague is caused by fleas.
  • Relapsing fever is caused by bedbug and body louse.

Poisonous insects

  • Many insects and larvae produce poisonous secretions injected into the body of man and other animals either through bite or sting.
  • Honey bees, hornets, wasps, fire ants, bedbugs, mosquitoes and few lepidopterous and larvae.

Productive insects

  • Human beings are greatly indebted to certain insects which supply them with useful products.
  • Many commercial products produced by insects are dispensable to modern man.
  • Honey bees, Apis produces honey.
  • Wax produced by honey bees are used in polishes.
  • Some scale insects also produce wax.
  • Silkworm, Bombyx mori produces raw silk.
  • Cantheridin oil used to restore hair is produced by Blister beetles.
  • Bees, wasps, flies help in pollinating flowers
  • Insects like dung beetles, maggots, feed upon waste materials like dead bodies and debris of plants and animals so preventing decay and obnoxious odors,.
  • Insects like locust, termites, Goliath beetle, large caterpillars, etc. are eaten as food.
  • Blow fly larvae are used in treating decay of tissues.
  • Bee-venom is used in treatment of some forms of arthritis and preparation of anti-venom to counteract snake bite.
  • Some insects are useful in biological control of other harmful insects e.g Aphids and scale insects are eaten by larvae and adults of ladybird beetles.
  • Predatory tiger beetles and nocturnal ground beetles destroy cutworms, armyworms, slugs and snails.

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