What are Arthropods?
Arthropods are biologically distinct groups of animals, whose physical characteristics and diversity enabled them to support a wide range of ecological communities through millions of years of existence. Arthropods are said to comprise about three-fourths of the animals existing on Earth and are found both on land and water.
Arthropods could take the form of: (1) insects (2) crustaceans (3) spiders (arachnids) (4) millipedes (diplopods) and (5) centipedes (chilopods). By this information alone, you have an idea of just how broad and diverse their domain could be; hence, the ecological importance of arthropods is immeasurable.
The easiest distinction for a creature to qualify as an arthropod would be its “jointed legs". In fact, the word arthro is of Greek origin, which means joints while poda refers to legs. Therefore, all arthropods have jointed legs.
Another distinction among arthropods are their bodies, which are divided into sections, wherein each section possesses a pair of legs for different purposes.
Arthropods possess exoskeletons, or external skeletal systems as body coverings, to protect an open circulatory system. These outer skeletons are what we actually see as outer shells, and are usually tough; although some do not have the same quality of hardness as others. Like their legs, these exoskeletons have certain uses essential for their interaction with the different members of the animal and plant kingdom in order to maintain biodiversity.
At this point, you now have an idea of what arthropods are. We will find out facts about the immensity of the arthropods’ ecological significance in two separate settings: their land and water habitats.
How Human Activities Affected Land Arthropods’ Ecological System
In the olden days, farming activities went on at a pace that was natural to man; hence, there seemed to be a balance of existence between human beings, plants, and animals.
However, as world populations grew, the human’s need for food increased and was demanded at a faster rate. Technological developments and advancements provided solutions that could increase food production in the agricultural sector. Land became widely used for commercial farming and grew increasingly important as a source of crops and vegetation.
However, the animals’ ecological system was being disrupted and the habitats of most insects, arachnids, centipedes, and millipedes were being destroyed. Hedgerows were brought down to expand the crop fields to far reaching realms.
These land arthropods’ natural instincts were to migrate and seek food elsewhere, where it could be found abundantly. It wasn’t long before they came back and discovered their old habitats but in a new form. The area became a vast region of field crops, orchards, and vegetations where they could resume their ecological communities and perform their natural functions.
Perhaps these arthropods initially rejoiced at the full concentration of food supply in a single location. They came in swarms because there was enough food for everyone, but their arrival was considered as plagues and infestations. Bees, wasps, and locusts provided the most problem to the farmers, since they were quite aggressive and antagonistic in attacking human beings that tried to drive them away from their new found habitats.
Different insects and worms were considered pests, since they fed on crop yields, which lessened the expected agricultural production. Man’s solution was to introduce pesticides and herbicides concocted from chemicals that could eradicate the pest’s existence. This modern solution was successful as they slowly eliminated crop infestation as a widespread agricultural problem.
The Ecological Importance of Land Arthropods Revealed
It wasn’t until later that pesticides were discovered to be harmful to man because they contaminated both soil and produce. However, continuous agricultural studies also revealed that crop yields were not as much as expected despite the absence of arthropod infestations. Agricultural scientists later realized that the winds were not sufficient to disperse the seeds, since different crops had different systems of releasing their pollens.
Scientists discovered that there are 29 species of insects responsible for pollination, and each species foraged for nectars. These species included bees, wasps, ants, butterflies, moths, flies and beetles, just to mention a few.
Pollens and grains became accidentally attached to their chests and legs and were transferred to other agricultural crops. Researchers soon found out that most plants actually produce scents to send signals to insects that food in the form of nectar was available.
They further learned from their studies that out of the pollens produced, only an estimated 10% are used to produce flowers for new fruits and that already meant good crop yields. The rest of the pollens are meant for the insects as enticements, so they would come to forage and open up their sacs, chew on their seeds, or to transport their pollens to where it could be useful.
The Importance of Pollination and Natural Pest Control to Agriculture
Extensive scientific studies revealed that different arthropod activities influenced pollination:
- The distance traveled by the arthropods to forage for food up to a distance of 10 kilometers.
- The period or season that they forage and store their food;
- The speed that different species of insects consume their stored food;
Initially, the farming sector went into large scale production of maize because it did not require pollination; but this did not provide the ultimate solution to what was ailing the commercial agricultural industries.
Cattle, to be of the best livestock breed, are ideally fed with alfalfa, forage legumes, and silage as the best sources of calcium and protein. The demand for good breeds of cattle stock could not be met because the supply of forage food was not enough. Studies showed that almost one-third of all cattle feeds made use of agricultural products that relied on pollination in order to have good crop results.
Seed dispersal needed enhancements; hence, most farms resorted to hand-pollination, since there were not enough insects foraging for food as inorganic fertilizers and pesticides affected their populations. Even their natural habitats were no longer available because other natural settings had been disrupted or converted to serve man’s purpose. Forests became denuded as trees were being cut down without any forethought, while most of the available land was filled with concrete edifices.
However, farmers came to realize the importance of pollination because manual pollination could cost them as much as additional 25% in labor costs. Based on agricultural statistics, an estimated annual cost of $11 million was being spent for hand pollination alone.
To remedy the situation, insects, mostly beetles, were imported and propagated in nest sites, which resulted to 20% increase in yield and savings of about $115 million in dispensing with hand-pollination.
Natural Pest Control
The roles of centipedes and millipedes as members of the land arthropods came into focus as studies were made on how plant diseases could be managed. Reports revealed that pathogenic fungi and bacteria that caused plant diseases, and even human illnesses, flourished because there was ecological imbalance between prey and predator.
There were not enough millipedes (diplopods) and centipedes (chilopods) in the ecological system to feed on the harmful fungal and bacterial growths which could control their numbers. The imbalance caused harmful microorganisms to flourish; it became difficult to manage plagues and diseases through natural processes.
Additional Ecological Benefits from Land Anthropods
There are other areas of ecological importance that can be derived from the arthropods’ seemingly harmful, yet beneficial, existence in our midst.
Cockroaches, spiders, mites, ticks and all other insects considered as carnivorous, prey on smaller species to maintain ecological balance. Hence, communities that have a good balance of these arthropods tend to have better pest control.
In fact, ecological significance becomes economic importance as human beings find more use in the substances secreted or produced by different arthropods:
- Bees produce honey and their honeycombs contain beeswax, widely used for manufacturing votive candles, furniture wax and polishes, ointments, lithographic inks, waxed papers, antiseptics, and fillings for surgical uses.
- The pollens stored in honey combs were discovered to have a rich mixture of vitamins, enzymes, and amino acids that could provide therapeutic benefits. They were used as ingredients for supplements and medications that could provide relief for ordinary ailments like colds, asthma, hay fever, influenza, and prostate disorder just to name a few.
- Bee propolis, which is a dark resinous substance produced by these arthropods as they feed on buds and barks of trees, was widely used for its antibiotic properties, even during ancient times.
- Silk producing arthropods, like those produced by caterpillars to protect their cocoons, were discovered to be strong enough to use and be woven into fabrics. Obviously, this discovery is an offshoot of ancient China’s silk industry, as they were the first to make use of the silkworm’s filaments as threads for their famous Chinese silk.
- In recent years, the spiders’ web was discovered as an additional material that could provide tensile strength; they became essential raw materials for Kevlar vests, fishing nets, surgical sutures, and adhesives as they contained natural antiseptics.
- An arthropod insect known as Laccifera lacca is the source of an organic resin known as shellac. The resin is produced from the insects’ cocoon and became useful for its coloring properties. It has been traced through natural history and the record of its use can be dated to 250 A.D.
These are only some of the well-known economic uses we derive from arthropods as indirect benefits, if the ecological system of the arthropods are not disrupted from their natural occurrences.
Water Arthropods’ Ecological Role
Water arthropods are represented by crustaceans in the forms of shrimps, crabs, lobsters, prawns, water fleas, barnacles, and krill. The latter are small shrimp-like aquatic creatures, and they represent the bottom of the aquatic arthropod’s food chain.
These water creatures move about independently and can easily migrate to where they can find food to sustain their communities. Their appendages allow them to swim without paying heed to the oceans’ currents and movement.
Krill, a basic food of larger aquatic arthropods, can be found abundantly almost anywhere, particularly where phytoplankton communities exist. This links them to the same environmental problems faced by fish ecologies, as described in the article The Ecological Importance of Fish.
The main importance of these animal species to human beings is their function in the food chain, and the indirect economic benefits mankind derives. The blue crab, as an example, provides livelihood to the coastal communities in the Gulf of Mexico, as major commercial capture fisheries provide jobs and other economic support .
The dockside values from their annual catch is estimated at $40 million based on reports of recent years’ sales. However, due to the continuous spate of environmental problems, including the recent BP oil spill disaster in the Gulf, the presence of the blue crab in the communities’ marsh edges and in seagrasses is said to be in critical conditions.
Lessons for the Future
There are still lessons to be learned; our own study of the ecological importance of arthropods is brief, and relies only on the findings of the scientific researchers. Nonetheless, it shows how we, as humans that belong to the top of the foodchain, could hardly experience any threat of being preyed upon by higher predatory levels. Hence, we carelessly demand, extract, utilize, and over exploit those that are below, as well as disrupt the natural resources used in their ecological system.
Perhaps the information gathered in this article will bring us to the realization that there is a need to revert to the natural order of the entire ecological system. Human beings admittedly cannot duplicate what the arthropods and fishes can do and produce, since efforts are being exerted to bring back these creatures. Otherwise, our links to the food chain could be broken, which could eventually sever us from our natural food sources.
Reference Materials and Image Credit Section
- All images courtesy of Wikimedia Commons