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Mosquito Olfaction and Behaviour
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An organism's behaviour results from the interaction between its genome and its environment. It is this interaction that allows organisms to respond to changing environmental stimuli. Specific behaviours are expressed as fixed action patterns that may be released in response to the receipt of a correct code by the sensory receptors that monitor the environment. In addition to the inherent action patterns, the physiological state or endogenous modulatory factors can modify the behavioural expression when biologically appropriate.
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The host-seeking behaviour of mosquitoes is primarily dictated by olfactory stimuli emanating from their hosts. Mosquitoes have evolved the ability to associate metabolic by-products, kairomones, produced by a blood-host and to use these odours in host location. Host preference differs between species, with some feeding almost exclusively on humans, while others prefer different mammals, birds or other vertebrates. These more or less stereotypic behaviours have been linked to genetic differences between species. Whether these variations are directly related to differences in the functioning of the olfactory system is currently unknown.
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In order to evaluate the importance of olfactory stimuli on mosquito host-seeking behaviour, we need to decipher the code that elicits this behaviour. This is currently being performed through systematic single sensillum recordings (SSRs) along with gas chromatography (GC) coupled SSRs from physiologically characterized olfactory sensilla in order to identify novel natural ligands from various hosts.
Selected references
Ghaninia M, Ignell R, Hansson BS. (2007) Functional classification and central nervous pro-
jections of olfactory receptor neurons housed in antennal trichoid sensilla of female yellow fever mosquitoes, Aedes aegypti. European Journal of Neuroscience. In press.
Ghaninia M, Larsson MC, Hansson BS, Ignell R. Identification of natural novel ligands for ORNs of female yellow fever mosquitoes, Aedes aegypti, using gas chromatography coupled single sensillum recordings. Submitted.
Functional genomic analysis of the mosquito olfactory system is a prerequisite to under-
standing the fundamental basis for host choice. With the recent molecular characterization of the olfactory receptors (ORs) of Anopheles gambiae and Aedes aegypti, we have taken a crucial step forward in unraveling the link between sensory receptors and host choice. By expanding on this topic through the identification of ORs in novel species, and the linking of ligands to ORs, we hope to increase our knowledge about the function of these receptors.
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The central nervous system plays an essential role in interpreting, integrating and responding to olfactory stimuli. In order to appreciate the functional characteristics and plasticity of the system, we have presented an extensive outline of the organization of the chemosensory centers. In addition, we have presented the first functional map of the primary olfactory centre of a mosquito.
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Selected references
Ghaninia M, Ignell R, Hansson BS (2007). Functional classification and central nervous projections of olfactory receptor neurons housed in antennal trichoid sensilla of female yellow fever mosquitoes, Aedes aegypti. European Journal of Neuroscience. In press.
Ignell R, Hansson BS (2005). Projection patterns of gustatory neurons in the suboe-sophageal ganglion and tritocerebrum of mosquitoes. Journal of Comparative Neurology 492: 214-233.
Ignell R, Dekker T, Ghaninia M, Hansson BS (2005). The neuronal architecture of the mosquito deutocerebrum. Journal of Comparative Neurology 493: 207-240.
Ghaninia M, Hansson BS, Ignell R (2006). The antennal lobe of the African malaria mosquito, Anopheles gambiae-innervation and three-dimensional reconstruction. Arthropod Structure and Development 36: 23-39.
Understanding the neural network of the olfactory system also requires information about the nature, distribution and modes of action of the chemical substances involved in neuronal communication. Using immunocytochemical markers we are currently identifying the distribution of neurotransmitters and neuromodulators in the olfactory system. This work will be complemented with molecular, physiological and pharmacological data to obtain valuable data concerning the functional role of these signaling molecules.
Selected references
Purayil S, Ignell R, Hansson BS. Immunocytochemical localization of serotonin in the central and peripheral chemosensory system of mosquitoes. Submitted.
Funding
This project is funded by Formas.
Personnel
Majid Ghaninia, Shahid Majeed, Siju K. Purayil, Sharon Hill, Senay Sengul, Bill Hansson, Rickard Ignell. Back to Projects >>>
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