The population ecology of termites and their role in natural and urban ecosystems

The urgency and relevance of the theme of the dissertation. The damage caused by termites around the world is growing year after year. The countries of Western Africa spend about 10% of the finance assigned for the repair of constructions on buildings damaged by termites. In the USA alone the restoration of buildings after termites costs $1.5 billion annually, while the annual figure around the world is $20 billion1.
Termites destroy all wooden elements in various constructions, such as architectural and cultural monuments, strategically important constructions, hydraulic structures and residential and administrative buildings. One termite family consisting of 25 thousand individuals and occupying a space of 100 cm3 consumes an average of 50,000 cm3 of different types of cellulose. At the same time, they have a huge impact on the global carbon cycle, increasing the concentration of carbon dioxide and methane in the atmosphere. The ability to digest cellulose, which results in the emission of CO2 is the outcome of combining termites’ digestive secretions and the simbionts’ enzymes and, the consequential biochemical processes.
Termites’ hidden life and strong resistance to environmental factors, as well as the functional specialization of their castes and their ability to restore populations within short periods, complicate the control. Thus, to develop up to date biological control methods and to research into termites’ population ecology and their relations with vertebrate and invertebrate animals and microorganisms arc the most important steps to be taken.
It should be noted that the available scientific knowledge is not sufficient to protect residential and other constructions from termites. A better understanding of the reasons why termites moved from their natural environment and distributed in urban ecosystems would significantly improve the protection of susceptive infrastructure. Thus, among today’s most urgent tasks arc to determine the current distribution of the termite population, to study the physiological and biochemical processes associated with the digestive secretions and the activity of the simbionts’ enzymes, to identify new nematode species parasitizing termites and to improve control methods through the development of new poisonous baits based on pathogenic fungi and microorganisms.
The research of this dissertdtion in a certain degree serves to the solution of tasks stipulated in the decree № PD-1940 of March 20 2013 «On the program of tourism development in Khorezm region for 2013-2015» of the President of the Republic of Uzbekistan and the decree № 27 2 February 2012 «On the acceleration of works aimed to control the termite population in the Republic of Uzbekistan and to prevent the harm they cause» of the Cabinet of Ministers of the Republic of Uzbekistan, and also in other legal documents adopted in this area.
The aims of the research is a comprehensive definition of population ecology of termites of the genus Anacanthotermes in natural and urban ecosystems of Uzbekistan and to develop of effective biological control methods of termite population.
Scientific novelty of the research is as follows:
for the first time for the global termite fauna nematode species Caenorhabditis sp. was discovered in termites;
the activity of the lactase enzyme in the salivary gland of termites of the genus Anacanthotermes was established;
for the first time 24 species of fungi inhabiting the termite’s body, its food and the termitarium’s chambers were identified and their species composition were established;
the virulence of the strain of Beauveria tenella (Del) Siem BD-85, which use in the fight against termites extracted from the moroccan locust was increased;
for the first time a pathogenic bait out of the sunflower stem and strain Beauveria tenella (Del) Siem BD-85, Bacillus thuringiensis was created, which can be used to control the termite population.
CONCLUSIONS
On the basis of the conducted research on a doctoral dissertation on the theme «The population ecology of termites and their role in natural and urban ecosystems» the following conclusions were presented:
1. The natural and urban territories of Uzbekistan arc populated by two termite species mainly: A. turkestanicus Jacobson, 1904 and A. ahngerianus Jacobson, 1904 of the genus Anacanthotermes
2. The population ecology and structure of termites from the genus Anacanthotermes in urban and natural ecosystems was identified. In such ecosystems, the life of termites is directly and indirectly associated to various vertebral and invertebrate animals.
3. The main reasons for the population and spread of termites over urban ecosystems. The distribution of A. turkestanicus and A. ahngerianus is impacted by a series of ecological as well as anthropogenic factors.
4. The digestion of oligomers by termites is defined by an effective exo- and cndoccllulase system. The study findings showed that the wood damage caused by termites, is associated to the carbohydrase activity of the salivary as well as intestinal glands and symbiotic enzymes.
5. Carbossimctilcellulose and cellobiase was inactive in the enzymes structure of all termites of the genus Anacanthotermes. For the first time the lactase enzymes participating in the digestion of termites of the genus Anacanthotermes were studied.
6. Twelve species were identified as symbiotic, flagellated protozoa that were involved in the digestion by A. turkestanicus and A. ahngerianus. The existence was proven of symbiotic relations between flagellated protozoa and termites of the genus Anacanthotermes, that from an evolutionally perspective points at close trophic and metabolieal link.
7. 24 fungus species were discovered in the soil of termite hills. In addition, the involvement of Alternaria, Cladosporium, Stemphylium, Stachybotry and Helminthosporium sp. was proven during the digestion by termites’.
8. For the first time for the global termite fauna nematode species Caenorhabditis sp. was discovered in termites. Micromycetes of Aspergillus, Beauveria, Penicillium, Fusarium, Alternaria, Cladosporium sp. were present in termites nests. Therefore the efficiency of fluids containing the fungi Aspergillus flavus, Aspergillus orysae, Beauveria bassiana, Beauveria tenella, Scopulariopsis brevicaidis and Fusarium sp. was tested for infesting termites. The results showed, infection rates ranging between 82% and 100%.
9. It was proven that cntomopathogenic bacteria emitted chemical substances of the Bacillus thuringiensis group known for its anti-termite activity against A. turkestanicus. The findings demonstrated that strains of Bacillus thuringiensis LMD and LME-22 were the most toxic to the termites species studied.
10. For the first time, an effective bait was developed - based on a mixture sunflower stems (Helianthus annuus L.) and strains of Beauveria tenella (Del) Siem BD-85 and Bacillus thuringiensis L. The developed baits, attracted termites and consequently were effective in controlling termite populations.
11. The developed baits containing the fungus Beauveria tenella (Del) Siem BD-85 could be transferred in a way that permits producing such baits in a form that can be used for as a large-scale, antitermite campaign.