Butterflies, Gut Bacteria and HARAI


Sometimes that gnawing sensation in your gut is a nervous reaction to one of life’s common challenges, other times the cause is something different.  When the former is the case, as from sitting in an unfamiliar office, nervously awaiting a job interview, or standing in the on-deck circle, seconds from facing the league’s best pitcher, the expression is: “I’ve got butterflies!” 

But what about the other times, when the cause of that queasy feeling isn’t nervous anticipation or excitement?  When the source is unknown, and the discomfort continues, or recurs, from one day to the next?  In this case, the recommendation is: “Call your doctor.”

While there are myriad common ailments of the digestive system, recent medical science has determined that many problems originate with imbalances in the gut microbiome.  Thousands of species of beneficial microbes and fungi, numbering in the trillions, populate our gut, performing various functions ranging from fermentation to immune response.  Yet we still don’t know much about where these bacteria originate, nor how they grow or coexist in our bodies.

In 2018, researchers trying to advance this science, and faced with the endless variability of diet, lifestyle and environment in humans, decided that an effective approach would be to focus on the digestive systems of a much simpler creature. 

They chose for their study subject lepidoptera - butterflies.

Traveling to La Selva Biologica, on the Caribbean coast of Costa Rica, the researchers undertook an exhaustive study of a few local species of butterflies.  The area offered several distinct habitats, including jungle and pastureland, and two categories of tropical butterflies, one fruit-feeding (frugivores), the other nectar-feeding (nectivores.)   

With advanced DNA testing and analysis, the researchers made several important discoveries:

  • Baby butterflies (larvae) have vastly different – and denser - gut bacteria than their parents.
  • Along with bacteria, butterflies have a lot of gut fungi, too, and these are primarily of the Saccharomycetales order – the “true” or “budding” yeasts that we use for baking and brewing.
  • A high percentage (80%) of the dietary bacteria (bacteria from food sources) of butterflies also lives in their guts; only 20-40% of dietary fungi survives there, indicating we naturally get quite a bit of our gut flora from the foods we eat. Not nearly so much fungi survives.
  • As in humans, butterflies often have rather different proportions and types of gut bacteria. This suggests that different bacteria might serve the same functions; two hosts can have his/her own peculiar colonies of gut microbes, and still be equally healthy.

While doctors are convinced that many illnesses, to say nothing of conditions of the digestive system, are caused by disruptions of the gut microbiome, understanding how the trillions of bacteria and fungi in our intestines get there, grow and function, is still largely terra incognita.  But it’s comforting to think that those beautiful flying insects are shedding some light on the mystery.   


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