1. Volume 26, Issue 1, Pages R41-R46 (January 2016)
Genes and Odors Underlying the Recent Evolution of Mosquito Preference for Humans 
Carolyn S. McBride 
Current Biology 
Volume 26, Issue 1, Pages R41-R46 (January 2016)
DOI: /j.cub
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2. Figure 1
Aedes aegypti aegypti has evolved a strong preference for human body odor.
(A) Map showing approximate distribution of the human-adapted Ae. aegypti aegypti (grey) and opportunistic Ae. aegypti formosus (black). The green oval marks the area along the coast of East Africa where the two subspecies coexist. Pie charts illustrate the results of ten published blood-meal analyses: field-collected blood-fed females were scored as having fed on a human or a non-human animal. Locations and references for subspecies aegypti (top row): Hawaii, USA [42]; Florida, USA [43]; Pate, Kenya [44]; Andaman/Nicobar Islands [45]; rural Thailand [46,47]. References for subspecies formosus and mixed populations (bottom row): Entebbe, Uganda [7]; Mombasa, Kenya [48]; Ganda, Kenya [7]. (B) An early example of host attraction and preference assays from 1973 in a two-port olfactometer [8]. Females are exposed to streams of air that have passed through a chamber that is empty or contains an odor source such as a live host. Mosquitoes flying upwind in either stream enter a trap from which they cannot escape. No-choice tests measure attraction to each host in isolation while choice tests measure preference. The two types of behaviors are related, yet distinct. For example, three strains of subspecies aegypti (grey bars) showed moderate attraction to a guinea pig in isolation, but strongly preferred a human when given a choice. All strains originated in coastal East Africa and were tested in the early 1970s. Bars show total percent response of 400 females tested in four separate trials of 100 each. Data for replicates were not provided, precluding statistical comparison.
Current Biology  , R41-R46DOI: ( /j.cub )
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3. Figure 2
Changes in peripheral olfactory genes associated with preference for humans.
(A) Schematic of peripheral olfactory system. The mosquito antenna, maxillary palp, and tip of proboscis (not shown) are covered with sensory hairs called sensilla (insets) that house olfactory sensory neurons. The tuning of individual neurons is determined by the binding specificity of several different types of proteins [32]. Odorant-binding proteins (OBPs) carry odorants through the aqueous lymph within each hair to the neuronal membrane, where odorant receptors (ORs), ionotropic receptors (IRs), or gustatory receptors (GRs) recognize them and cause the neuron to fire. Individual receptors and OBPs recognize only a subset of odorants and therefore confer specificity to the neurons or sensory hairs in which they are found. Other accessory proteins may also contribute. There are three major morphological types of olfactory sensilla (insets). Capitate pegs on the maxillary palp house one neuron expressing carbon-dioxide-sensitive GRs and two neurons expressing select ORs ([32] and references therein). Trichoid and grooved-peg sensilla on the antenna house neurons that likely express ORs and IRs, respectively, based on odor-response profiling [49]. Evolutionary changes in the sequence or expression of peripheral olfactory genes may contribute to host preference by making the mosquito more or less sensitive to specific human and animal odorants. (B) The number of all antennal genes or differentially expressed antennal genes in Ae. aegypti that belong to the OR, IR, and OBP families [10]. ORs, but not OBPs and to a lesser extent IRs, were enriched among genes differentially expressed in human-preferring compared with animal-preferring subspecies and F2 hybrids. Asterisks indicate significant enrichment at the p < level. (C) The number of human and non-human odorants for which cognate An. gambiae/coluzzii ORs were upregulated or downregulated by at least 10% (on average) relative to those of the animal-preferring An. quadriannulatus [38]. Fisher’s exact test p = 0.04.
Current Biology  , R41-R46DOI: ( /j.cub )
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