Investigations into the oviposition behaviour of the mosquito Anopheles gambiae

The Anopheles gambiae species complex includes the most predominant malaria vectors in sub-Saharan Africa. How they locate oviposition sites is not fully known, but a greater understanding of this subject may lead to more effective monitoring and trapping of gravid females. This project investigated potential oviposition semiochemicals and the oviposition behaviour of An. Gambiae sensu stricto Giles. The volatile profiles of seven bacteria were analysed by gas-chromatography linked mass-spectroscopy (GC-MS) to determine their volatile profiles and behavioural assays to determine their effect on An. gambiae. Cage assays could not confirm attraction to bacterial solutions, but demonstrated repellence to 4-methylphenol at 1mg/ml. GC-EAG demonstrated a strong electrophysiological response to 4-methylphenol and 8 of the 9 bacterial chemicals tested gave at least 50% of the 4-methylphenol response. Direct observations of oviposition in a large arena showed that, compared to a control dish of 0.9% saline, 1mg/ml 4-methylphenol reduced the number of visits, proportion landing and visit duration, but did not completely deter oviposition. A choice between dishes of saline or 1mg/ml 4-methylphenol, showed the latter was highly repellent; a majority of females oviposited in the control, the number, proportion and duration of visits to treatment dishes were reduced and fewer eggs were laid per female. When 4-methylphenol was presented separately from water in porous sachets, the repellency was shown to be largely volatile based, having an effect on the direction of approach to dishes, but no deterrence of egg-laying in dishes near the sachets. Short range cues, possibly involving substrate contact/sampling, appear to mediate the final stages of oviposition site selection. These findings are discussed in the context of utilising a more holistic approach than previously used to study mosquito oviposition; oviposition is clearly not a single behaviour, but a complex chain of sensory inputs and responses by the gravid insect.

Name dc:type.qualificationname

phd

Level dc:type.qualificationlevel

doctoral

Grantor dc:publisher.institution

University of Greenwich

Year dc:date.issued

2015

Author dc:creator

• Broom, James William

Advisors dc:contributor.advisor

• Gibson, Gabriella
• Hall, David

• QL Zoology
• QR Microbiology

Language dc:language

en