Taste Neurons Detect CO2

Biological Strategy

Common fruit fly

AskNature Team

Image: Géry Parent / CC BY ND - Creative Commons Attribution + NoDerivatives

Sense Chemicals (Odor, Taste, etc.) From the Environment

Chemicals are important for signaling and communication among living systems, either intentionally (such as when two living systems try to find one another) or unintentionally (such as when a plant emits a chemical signal that an herbivore can use to find a tasty bite). They are also important for other uses, such as navigating or finding sources for minerals. But chemical signals are often relatively weak and disperse when moving through water or gases. Therefore, detecting them requires specialized abilities, including a way to determine where they are coming from. A well known example of sensing chemicals can be seen in ants following a pheromone trail laid down by others in their colony to locate a quality and abundant food source.

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Insects

Class Insecta (“an insect”): Flies, ants, beetles, cockroaches, fleas, dragonflies

Insects are the most abundant arthropods—they make up 90% of the animals in the phylum. They’re found everywhere on earth except the deep ocean, and scientists estimate there are millions of insects not yet described. Most live on land, but many live in freshwater or saltwater marshes for part of their life cycles. Insects have three distinct body sections: a head, which has specialized mouthparts, a thorax, which has jointed legs, and an abdomen. They have well-developed nervous and sensory systems, and are the only invertebrate that can fly, thanks to their lightweight exoskeletons and small size.

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Specialized taste neurons of fruit flies detect CO2 to mediate taste acceptance.

Image: Géry Parent / CC BY ND - Creative Commons Attribution + NoDerivatives

Female Drosophila melanogaster

“There are five known taste modalities in humans: sweet, bitter, sour, salty and umami (the taste of monosodium glutamate). Although the fruitfly Drosophila melanogaster tastes sugars, salts and noxious chemicals, the nature and number of taste modalities in this organism is not clear…Here we identify a novel taste modality in this insect: the taste of carbonated water…The taste of carbonation may allow Drosophila to detect and obtain nutrients from growing microorganisms. Whereas CO₂ detection by the olfactory system mediates avoidance, CO₂ detection by the gustatory system mediates acceptance behaviour, demonstrating that the context of CO₂ determines appropriate behaviour. This work opens up the possibility that the taste of carbonation may also exist in other organisms.” (Fischler 2007:1054)