Why maggots love the texture of decaying fruit

Most research on food sensation has focused on tastes like sweetness or saltiness. But preferences for food often depend on their texture; some might like the flavor of mushrooms, but not the rubbery feeling in their mouths. While tasting flavors requires chemical sensation, tasting texture requires mechanical sensation, and it is unclear whether taste organs like the tongue have this capacity. The new study addressed this issue in fruit fly larvae, commonly called maggots, because of the simplicity of their nervous system and the available genetic tools.

The researchers established that maggots will not eat food that is too hard or too soft, but if it is just right -- corresponding to days old decaying fruit -- they dig in. Hypothesizing that this ability to sense food texture takes place in the peripheral taste organs, the researchers selectively disabled taste neurons in the larva mouth. As a result, the maggots lost their sense of taste texture and tried eating food that was softer or harder than their usual preference. Further experiments revealed that the painless mechanoreceptor gene is required for this sense. Lastly, they found that the C6 neuron in the maggot taste organ can sense both sugar and mechanical stimulation, meaning that the same neuron can taste food texture and food substance. Taste sensation and signal integration is thus quite different from other systems, and investigations beyond fruit flies are needed to fully understand taste perception in mammals, including humans.

The authors add, "Food texture remains a neglected attribute of overall food fitness. We find -- with the power of Drosophila genetics -- that at least the hardness of food is a crucial aspect of the overall gustatory profile. Excitingly the same neurons that sense chemicals in the taste system can in some cases sense texture."