It’s a problem that parents know all too well: a child won’t eat because their oatmeal is too slimy or a slice of apple is too hard. Is the kid just being finicky? Or is there a biological basis for disliking food based on its texture? This image, showing the tongue (red) of a fruit fly (Drosophila melanogaster), provides some of the first evidence that biology could indeed play a role .
The image shows a newly discovered mechanosensory nerve cell (green), which is called md-L, short for multidendritic neuron in the labellum. When the fly extends its tongue to eat, the hair bristles (short red lines) on its surface bend in proportion to the consistency of the food. If a bristle is bent hard enough, the force is detected at its base by one of the arms of an md-L neuron. In response, the arm shoots off an electrical signal that’s relayed to the central part of the neuron and onward to the brain via the outgoing informational arm, or axon.
What’s interesting is the md-L axon connects directly to the brain’s taste center. That’s where incoming signals arrive from other neurons at the base of the hair bristle that offer information about the taste of this food item. All the information is integrated into one immediate choice: to eat or not to eat? If the textural concern from the md-L neuron is prominent enough to override the attraction of taste, the fruit fly will look elsewhere for its next meal.
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