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. 2013 Sep 12;9(9):e1003710. doi: 10.1371/journal.pgen.1003710

Figure 3. The primary olfactory system and acidity are dispensable for perception of fatty acids.

Figure 3

A) Flies were split in two groups, one used as intact control (intact) and the other with antennae and maxillary palps surgically removed (antmxp-). B) No differences were observed in flies with antennae and maxillary palps surgically removed (antmxp-) compared to intact controls (intact) while flies were tested for PER response to HxA, fructose, sucrose and to yeast extract. C) Intact flies and antmxp- flies do not show difference in preference for FA (HxA 0.01%) or in avoidance (HxA 5%) in the CAFE assay. D) Preference of FAs is specific and is pH independent. Flies strongly prefer 0.1% HxA and 0.1% OcA, show weak preference for 0.1% acetic acid (AcA) and no preference for 0.01% hydrochloric acid (HCl) when tested at pH∼3.5. Flies do not show preference for high pH (NaOH, pH∼9.5). E) Flies prefer HxA and OcA over HCl at matched acidity (pH∼3.5). HxA diluted in PBS buffer tested against PBS retains strong preference for HxA at the neutral pH (pH∼7.2–7.4). All data, mean ± s.e.m. ** p<0.01, *** p<0.001; NS, not significant, t-test.