Thursday , 15 November 2018

Termite destruction may free viruses

Nandkumar Kamat

In the January 2014 issue of  the ‘Smithsonian Magazine’, Paul Bisceglio introduced Helen Esser, a fellow at the Smithsonian Tropical Research Institute in Panama City, who chose to survey bloodsuckers. Paul informed that “she spent three months on the Panama Canal, dragging cotton cloths across forest floors to collect 20,000 ticks. After dropping them into alcohol-filled jars, she carried them back to the lab and catalogued them, tick by tick, to get at a pressing global-health question: Does chopping down forests spread deadly diseases?”

We need to ask a similar question in Goa – would uncontrolled trade in Termitomyces species, the wild edible mushrooms cultivated by the fungus grower termites lead to deadly viral diseases? Because if these mushrooms are not permitted to mature and discharge their spores for the termites then it would be impossible for them to maintain their underground fungus gardens leading to complete collapse of the social insect society. Once the fungus grower termite system in forests of Goa collapses what would happen to the litter which is processed by this system? It is a reservoir of several known and unknown dreaded viruses. It has been found that as compared to any other soil, the forest soil has more virus particles on earth.

The dead material from plants, animals, insects etc, mainly all solid biodegradable organic matter, accumulates on the floor as litter. This litter needs to be processed to return the locked minerals C, N, P, Ca, Mg, Si , Fe, Na, K etc back to the soil nutrient pool. There is another dimension of this litter – it is natural quarantine which immobilises some of the most dreaded viruses like KFDV (Kyasnur Forest Disease Virus).  Kyasanur forest disease virus is transmitted by the bite of the tick Haemaphysalis spinigera, a tick often found at the edge of the forest margins. Rodents, bats and shrews as well as monkeys are also susceptible to the virus.

Human interference under the pressure of market economy is slowly creating an imbalance in the ecosystem. Why are fungus growing termites important? People who consume the mushrooms don’t know that they are creating a serious imbalance in the ecosystem spelling doom for Goa because in no other Western Ghats state is the trade in wild local edible mushrooms so high. It would reach Rs10 crores this season because the rate per each mushroom has reached Rs20. In tropical regions, termites influence the structure and functioning of ecosystems through the agency of mound building and maintenance of a fungus garden. Lee & Wood in 1971; Lobry de Bruyn & Conacher in 1990; Konaté and others in 1999; Holt & Lepage in 2000 have done extensive work on importance of termites in recycling dry organic matter and in modification of soil texture and structure. Wood & Sands in 1978 and  Josens 1983 proved that termites create huge impact on carbon cycling by processing large quantities of plant material.

The mound builder, fungus grower termites in Goa from Macrotermitinae subfamily form an obligate exosymbiosis with the fungus Termitomyces. What is the processing rate of these termites? The studies in Malaysian forests by Matsumoto & Abe in 1979, ecosystem similar to Goa showed that 1400 kilograms of litter per hectare per year is consumed by termites. In Kenya, Buxton in 1981 found that 90 per cent of dead wood was degraded by termites in a semi-arid savannah – like the grasslands on plateaus we have in Goa teeming with termite activity. Josens in 1983 showed that in the humid savannah of Lamto in Ivory Coast, termites use about 27 per cent of the annual litter production. Termite recycling efficiency in Goa is estimated based on global turnover indicators to be 12 per cent of the total above ground primary production from herbaceous and woody plants.

Thus on average the termites contribute to mineralisation of 558 grams of carbon for every square metre per year. This mineralisation is impossible without the active agency of the Termitomyces fungus which they cultivate underground. The powerful extracellular enzymes from this fungus – cellulases, pectinases, ligninases, polyphenoloxidases, amylases, xylanases attack the Cellulose, Pectin, Lignin, Phenols, Starch, Xylan in the organic matter and convert these into simple compounds. So finally removing these factories of enzymes means creating huge difference in mass transfer relation.

Considering 1200 square kilometres area is under the forests of Goa, the total mineralisation of carbon per year by the fungus grower termites would be about 670000 metric tonnes. There is another dimension – the immobilisation of bacterial, fungal and viral pathogens associated with mixed forest litter. These pathogens cannot move because the termites plaster the litter and carry tiny fragments inside their nests. So automatically the immobilised pathogens are destroyed by the termites and their biomass too gets mineralised and returned to the soil nutrient pool.

Once these termites find that no decomposing tissue or spores are available after mushroom pickers collect everything from their habitat-the stressed termites cannot regenerate fresh fungus gardens easily. The colony then collapses followed by collapse of the termite mounds. With no fresh recruitment of new termite queens to start new fungus gardens with new workers finally the whole cycle may come to a halt. When that happens, the first sign would appear in the form of a new viral disease from Goa’s forest which would be submerged in mountains of litter.

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