Odour sensitivity of antennal olfactory cells underlying grooved pegs of Anopheles gambiae s.s. and An. quadriannulatus

Abstract

In female mosquitoes of the anthropophilic species Anopheles gambiae Giles s.s. and the zoophilic An. quadriannulatus Theobald single sensillum recordings from grooved pegs were made. In both species, the majority of these sensilla responded to ammonium hydroxide, butylamine and propanoic acid, whereas a smaller part responded to acetone. Lactic acid, butanone, 3‐methyl phenol and 1‐octen‐3‐ol evoked responses in a minority of grooved pegs only. In An. gambiae these four substances evoked either excitatory or inhibitory responses. In An. quadriannulatus excitatory and inhibitory responses were only found on stimulation with lactic acid; butanone, 3‐methyl phenol and 1‐octen‐3‐ol only evoked inhibition in the pegs of this species. More than half of the grooved pegs responded to water vapour with an increase in spike frequency. As opposed to this, in some pegs inhibitory responses were found upon stimulation with vapour of low humidity. This suggests that grooved pegs may play a role in humidity perception in Anopheles. Dose‐response relations were investigated for cells excited by ammonium hydroxide, butylamine and propanoic acid. Excitatory responses to these three substances were dose‐dependent. No significant differences were found between the dose‐response curves of the two species. It is concluded that in both species the host odours tested are not perceived by specialist cells. Combined information from generalist cells may provide a detailed ‘odour profile’ of the host.

Water vapour is a pre-oviposition attractant for the malaria vector Anopheles gambiae sensu stricto

“…Recent studies with An. gambiae s.s. have confirmed that more than half the grooved pegs on the antennae increase their firing rate in the presence of water vapour and that some respond to low humidity, suggesting that these receptors play a role in humidity perception [28]. Whilst it has been shown that humidity is important for the survival of mosquitoes [29], a clear difference in the behaviour of unfed and gravid females was demonstrated in the presented WHO tube experiments.…”

Live calcium imaging of Aedes aegypti neuronal tissues reveals differential importance of chemosensory systems for life-history-specific foraging strategies

“…2d, e, Additional file 10: Figure S4, Additional file 11: Figure S5A). Interestingly, 1-octen-3-ol, a known mosquito adult attractant produced by microbes [43], displayed the greatest calcium response, followed by butylamine and ethyl acetate, with the former previously documented to induce a response in activated grooved-peg OSNs in Anopheles gambiae , Anopheles quadriannulatus , and Culex quinquefasciatus [27, 44]. Moreover, when observing muscle responses to the same stimuli we observed significant calcium increases in 5 of the 6 stimuli that also displayed significant responses in the DE.…”

Olfactory regulation of mosquito–host interactions

“…quadriannulatus and An. atroparvus (Van Thiel) (Broek and Otter, 1999;Broek and Otter, 2000). At the peripheral level, no major differences in responses to several host volatiles were observed between these mosquito species with known differences in zoophilic and anthropophilic feeding preferences.…”