Submitted to: PLoS One
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/6/2011
Publication Date: 11/16/2011
Citation: Manoukis, N., Baber, I., Diallo, M., Sogoba, N., Ribeiro, J.M. 2011. Seasonal climate effects anemotaxis in newly emerged adult anopheles gambiae giles in Mali, West Africa. PLoS One. Interpretive Summary: Our paper describes the results of our two year investigation into the direction of movement of the major malaria vector An. gambiae in its first hours as an adult. We found a seasonally variable effect of the wind on mosquito movement by employing a custom enclosure with exit traps in multiple directions and analyzing the directions in which mosquitoes were caught via "dispersal vectors" a novel approach to quantifying the direction of insect movement in the field. Our results did not show a pattern of movement towards the village, but we did find consistent movement directions which are correlated with the direction of the wind and the season. During the wet season, under humid and warmer conditions, movement direction tended to be upwind. However, during the dry season, under dry and cooler conditions, movement directions were predominantly downwind. These results indicate that anemotaxis in An. gambiae should be closely examined under controlled conditions of varying humidity, temperature and wind speed.
Technical Abstract: The direction and magnitude of movement of the malaria vector Anopheles gambiae Giles has been of great interest to medical entomologists for over 70 years. This direction of movement is likely to be affected by many factors, from environmental conditions and stage of life history of the mosquito to the existence of attractants in the vicinity. We report here the direction of movement of newly-emerged An. gambiae in nature, around the village of Doneguebougou, Mali. We assessed the direction of movement for individual mosquitoes by placing them in a novel enclosure with exit traps oriented in the direction of the cardinal and intermediate points of the compass. We consistently found predominantly Southward directions of movement during 2009 and 2010, with an additional Eastward component during the dry season and a Westward one during the wet season. Our data indicate that wind has an important effect on the direction of movement, but that this effect varied by season: average directions of movement were downwind during the dry season and upwind during the wet season. A switch in anemotactic response suggests that the direction of movement of An. gambiae relative to the wind immediately after emergence under varying conditions of humidity should be further investigated under controlled conditions.