Many of us enjoy a cup of coffee a day, but the coffee berry borer beetle (Hypothenemus hampei) takes this to the extreme and spends its entire life cycle living on coffee beans. Caffeine is a toxin and is typically a deterrent to most insect herbivores. Somehow, the coffee berry borer overcomes this toxicity and enjoys an everlasting caffeine hit. Now scientists have discovered how the coffee berry borer can do this.
The answer lied in the guts of the beetle. Scientists performed an experiment where they sterilised the guts of some beetles so they no longer contained microbiota or bacteria. Following sterilisation, the beetle could no longer detoxify caffeine. Therefore it was not the beetle, per se, that could “eat” the caffeine but the symbiotic microbiota in the gut.
There were many different species of bacteria in the guts of the beetle, but the scientists found that one particular species primarily detoxified caffeine. The presence of this bacteria in the gut of the beetle enables it to live exclusively on coffee beans.
Bacteria need the right environmental conditions to exist. Some bacteria can exist in aerobic (presence of oxygen) environments whereas others can only exist in anaerobic (absence of oxygen) environments. To assess the oxygen environment of the beetle’s gut, the scientists measured oxygen with a Unisense oxygen microsensor. They found there was a region, less than a third of a millimeter in size, in the gut of the beetle that had oxygen. This microaerophilic region enabled the caffeine detoxifying bacteria to exist.
The coffee berry borer is only about 2mm in length, but this insect can have a devastating effect on coffee production. Yearly losses, in Brazil alone, are in the order of $300 million. Understanding the biology and ecology of the coffee berry borer will lead to better management of this pest species.
Watch a You Tube video on the coffee berry borer and its impact on the quality and cost of your coffee:
Ceja-Navarro et al (2015). Gut microbiota mediate caffeine detoxification in the primary insect pest of coffee. Nature Communications, 6: 7618.