Olfactory systems across mosquito species

Abstract

There are 3559 species of mosquitoes in the world (Harbach 2018) but, so far, only a handful of them have been a focus of olfactory neuroscience and neurobiology research. Here we discuss mosquito olfactory anatomy and function and connect these to mosquito ecology. We highlight the least well-known and thus most interesting aspects of mosquito olfactory systems and discuss promising future directions. We hope this review will encourage the insect neuroscience community to work more broadly across mosquito species instead of focusing narrowly on the main disease vectors.

Keywords: Brain; Evolution; Mosquitoes; Neuroethology; Neurons; Olfactory organs; Receptors; Sensory ecology.

Fig. 1

Olfactory organs of mosquitoes. Solid arrows point to antennae, dashed arrows point to maxillary palps, arrowheads point to proboscises. f—female, m—male. Image credits: A1. Anopheles freeborni female (https://www.inaturalist.org/observations/171373, Don Loarie), A2. Anopheles punctipennis male (https://www.inaturalist.org/observations/48198941, Katja Schulz), B1. Aedes alternans female (https://www.inaturalist.org/observations/50594863, Wendy Moore), B2. Aedes albopictus female (https://www.inaturalist.org/observations/32721364, Zygy), B3. Aedes triseratus male (https://www.inaturalist.org/observations/44504824, skitterbug); C1. Uranotaenia sapphirina female (https://www.inaturalist.org/observations/50204034, Arturo Santos), C2. Uranotaenia sapphirina male (https://www.inaturalist.org/observations/24801804, Even Dankowicz), D1. Toxorhynchites brevipalpis female (https://www.inaturalist.org/observations/45377361, Alan Manson), D2. Toxorhynchites rutilus female (https://www.inaturalist.org/observations/21372632, Katja Schulz), D3. Toxorhynchites speciosus male (https://www.inaturalist.org/observations/18770512, Steve Kerr); E1. Psorophora ferox female (https://www.inaturalist.org/observations/20379672, Katja Schulz), E2. Psorophora ferox male (https://www.inaturalist.org/observations/9620348, skitterbug), F1. Culex pervigilans female (https://www.inaturalist.org/observations/54584455, Steve Kerr), F2. Culex quinquefasciatus female (https://phil.cdc.gov/Details.aspx?pid=4734, James Gathany), F3. Culex quinquefasciatus male (https://www.inaturalist.org/observations/23073942, skitterbug); G1. Coquillettidia perturbans female (https://www.inaturalist.org/observations/19518594, Even Dankowicz), G2. Coquillettidia perturbans male (https://www.inaturalist.org/observations/6867156, Judy Gallagher), H1. Sabethes cyaneus female (https://phil.cdc.gov/Details.aspx?pid=20514, James Gathany), H2. Sabethes glaucodaemon female, and H3. Sabethes glaucodaemon male (both Image library of Coleção de Culicidae-Fundação Oswaldo Cruz, Rio de Janeiro, Brazil (CCULI))

Fig. 2

Olfactory innervations of Anopheles gambiae brain. Axons of olfactory receptor neurons located in the antennae and maxillary palps (thin green dashed lines) innervate specific subsets of glomeruli in the antennal lobe (AL). Axons of olfactory neurons located in the labellum (thick green dotted line) innervate 8 glomeruli-like structures in the suboesophageal zone (SEZ). The image depicts the brain and peripheral olfactory organs of an adult female Anopheles gambiae. Cell bodies of ORCO+ neurons are labelled with GFP