Ants: The Super-organism
We humans recklessly crush tiny, but elegant ants under our feet unaware of the fact that these creatures are an important and indispensable part of our ecosystem. These tiny creatures have been on earth much before the arrival of human race. Ants originated 145 million years ago and were witness to the extinction of dinosaurs.
Since their origin, ants have evolved to become the most dominant creatures in terrestrial ecosystem. They constitute 25% of the total animal weight in the tropics. Because of their great adaptability, these creatures have occupied every possible niche or habitat found on land. They have colonized forest canopies, dug underground tunnels, made nest in rotten logs, crevices, etc. and braved the freezing temperatures of high altitudes to be part of high altitude ecosystem.
Ants are now – a – days considered as super-organism and this status has been well illustrated and described in recently released book on ants called "Super organism" by Pulitzer Prize winner writers E.O. Wilson and Bert Holldobler. According to them "a Super organism is a colony of individuals self-organized by division of labor and united by a closed system of communication."
Ant colonies display traits similar in function to the cells and organs of a bigger organism like humans. The function of an ant colony can well be understood by comparing it to a human body. The cells in a human body parallels colony members; organs parallels castes; gonads parallels reproductive castes; somatic organs parallels worker castes; immune system parallels defensive castes; circulatory system parallels food distribution including trophallaxis, distribution of pheromones and chemical cues, sensory organs parallels combined sensory apparatus of colony members; nervous system parallels communication and interaction among colony members and skin and skeleton of a human body parallels nest of these great creatures.
Ant colony is composed of millions of individuals and these individuals exhibit a variety of behaviors e.g. cooperation with nest mates, defending the nest from robbers, organizing food raids and finding the best food, tending the immatures in the nest etc; all targeted at improving the survival chances of their colony unlike most of the human beings, who are self centered, selfish and are always working for the downfall of their fellow beings.
Ant colony is built up by queen ant. After nuptial flight, fertile female ant finds a suitable nesting site for laying eggs. The eggs hatch into tiny larvae. The first batch of larvae is tended by the queen itself. The larvae change into pupal stage and finally the first batch of workers emerge. These workers then take up the responsibility of feeding the young ones i.e. the larvae as well as the queen. The worker caste works on the principle of division of labor and differentiates into soldier caste, foragers, feeders etc. In this way ant colony is established.
While performing all these tasks thousands of workers need to communicate for smooth functioning of the colony. The ants do not communicate verbally, or visually or with the help of auditory signals. These creatures use the language of chemical cues to communicate with each other. Ants release specific chemicals along with tactile cues (tapping each other's antennae) to elicit a specific response from fellow workers. These chemicals are called pheromones. They use blend of chemicals for recruitment of nest mates for collecting food; or to alert entire colony when attacked by intruders. Moreover, a unique colony odour is present in each ant’s nest. The source of odour is the queen ant. All ants from one colony would therefore have a very similar odour and in this way can recognize nest mates from non nest mates.
By using these chemical signals ants remove dead bodies of fellow mates and debris to maintain hygiene of the nest, on contrary some species keep fragmented body parts of their colleagues as remembrance in their nests. Recently, it has been reported that like all other advanced mammal societies these creatures also show dominance and subordination and territorial behavior. Probably the ants have acquired these traits of behavior much earlier as compared to other animals including human species. Thus, the chemical signals act as a specific coded language conserving visual and auditory energy which even our human species cannot boast off.
Many other interesting behaviors are exhibited by ants e.g. some like Harpegnathos show jumping behavior, some feign death when captured, some show aggressive postures etc. Another form of behavior which is elucidated by many ant species like Formica (native to Himalaya and other parts of the world) is known as slavery. These ants raid other ant colonies capture their brood and workers, tame and use them for their own household chores.
Many of the ants have been grouped/classified on the basis of peculiar tasks performed by them. The major groups are:
Harvester ants: - The harvester ants have been named so as they harvest seeds of different types of grasses. These can be easily spotted in a garden, park or lawn where they create, corridors or passage on land which look like passages created by repeated movements of humans on grass lawns. These ants move in tandem, like many of the ant species have variety of worker force based on size and collect grass seeds. These bring grass seeds to their nest and store them in well kept godowns. Interestingly, harvester ants remove the plumule of seeds so that the seeds may not germinate in their nests and can be stored as food for long time. After consumption the hard seed coats are thrown out of the nests and can be noticed in abundance around their nests. Thus they help to maintain our terrestrial ecosystem.
Weaver ants:- As the name suggests they weave nest with leaves. One of the prominent groups in this category is red ant known as Oecophylla. These can be spotted on mango, citrus and guava trees and are quiet ferocious in nature. They don't nest in soil; instead exhibit marvelous architecture and intelligence to build their nest with leaves. The workers capture their little ones called larvae quite delicately in their jaws and move them to and fro on the edges of young tender leaves, in response to this movement or tricky feeling, little ones release sticky material from their glands. Then the other workers fold these leaves and join them with the secreted glue. To join two leaves which are quite apart from each other, ants’ form a chain by holding waists and thus pull the leaves together. This so called glue is known as silk (different from the silk secreted by silk worm). In mango or citrus orchards their nests are a delight to watch and even show great degree of sophistication as compared to bird's nests. They are a unique example of unbinding co-operation and high degree of unselfishness.This group is well spread in South – East Asia. By occupying fruit– yielding trees these ants have shown tremendous potential in recent years to be used as biological control agents. The trees harbored by these ants show more fruit yield and produce healthy fruits. The red ants protect the fruits from other pests, thus ensure that their host tree is equally benefitted. In Thailand, Malaysia, some parts of Indonesia and Australia farmers and scientists are using these ants for production of better fruit quality and increase fruit yield. With expertise the nests can be easily shifted from one tree to another and these ants show remarkable adaptability to weave nests on the introduced trees. Other interesting aspect regarding these ants is that these are used in Chinese drugs, in soup and in some parts of South – East Asia their dried powder is considered as aphrodisiac. Thus like other ants weaver ants also ensure the survival of human race.
Leaf – Cutter Ants:- The ultimate super organism with best and most complex communication system known in animals, air conditioned nest architecture. Human agriculture, which originated about 10,000 years ago, was a major cultural transition that catapulted our species from hunter/gatherer life style to a technological and increasing urban existence, accompanied by enormous expansion of population. Humanity thereby turned itself into a geophysical force and began to alter the environment of the entire planetary surface. Approximately 50-60 million years before this momentous shift, leaf cutter ants have already made the evolutionary transition from a hunter/gatherer existence to agriculture (Holldobler &Wilson in Super-organism). The leaf cutter ants cultivate fungi in their nests and are restricted in their distribution to New World. These ants bring fresh leaves and plant cuttings into their nests; these are further cut into smaller and smaller pieces and are treated with ants’ fecal liquid. Then these are inserted into that part of nest where fungus is cultivated. Fungus keeps on proliferating on these leaves and ants begin to feed on fungus. The fungus structures are rich in carbohydrates and proteins. Interesting aspect of the story is that even the most advanced human species if is forced to live with fungus culture may not be able to bear the brunt of pathogens but these super organisms are least susceptible to such infections. The resistance developed is unparalleled in any form of life.The leaf cutter ants are of immense importance in tropical and sub tropical ecosystem and are also major pests in cultivated fields of Central and South America and harvest about 85-470 kg (dry weight) total plant biomass per colony per year. Probably, not feasible even for human species to harvest and process such enormous amount of plant material as carried by leaf – cutter ants.
Army ants: - It is a treat to watch a moving column of these ants in tandem and rhythm without exchanging a single word, can make the most efficient army of the world envious. Rarely you find that out of thousand to million of ant workers moving in a column get distracted or loose rhythm or direction. As the story goes, some of the workers of group Dorylus of army ants are great predators, many a times their attacks capture small mammals as efficiently as a python. In tribal Africa, mothers working in fields have lost their new borns to the marching column of these ants. They show tremendous sense of chemical communication and in some cases workers are blind. Some of these also act as pests of potato crop. Thus, army ant represent highest peak of togetherness and precision in attack and give horrified image to human species as a dinosaur would have given in its prime time.
Let their natural intricacies apart as discussed in preceding text, they play an important role in our survival as well. They are an important component of our food chain and suppose if they perish human species may not be able to generate resources and clear debris from earth and may perish. It is really unfortunate in present scenario that much emphasis has been laid on those natural resources which are of direct importance to humans and to look for alternative resources in the wake of exhaustion of natural resources. And human intellect authoritatively terms it "The Development". If a species like humans considers itself the most advanced intellectual species on earth among other creatures, then it must take into account that survival is always reciprocative.
Ants provide many services free of cost which ensure the survival of our race. They are the major soil turners, channelers of energy, pollinators, scavengers, biological control agents and to sum up the ants are important component of food chain. More recently they are being used as indicator organisms which provide us cues regarding our deteriorating ecosystems. In developed nations like Australia, this concept has already been used effectively. In India too, for the first time this potential of these tiny creatures is being put to practice for assessing the health of Himalayan montane systems which is deteriorating due to growing human activities. It is high time that we pay attention to organisms for our survival and follow the famous epithet "Live and Let Live".
Copyright: Dr Himender Bharti