There Are a Ridiculous Lot of Invertebrate Traces in Your Cup of Tea

We biological humans are sloppy creatures that leave traces of our old selves everywhere we go, including in the air. Various secretions, like as saliva and discarded trash, are included in this self-trail. and our continually losing outer layers, which carry our unique DNA profiles, much like dead skin cells.

Bugs are no different. Invertebrates, from spiders to beetles, leave a trail of evidence in their wake, even over any budding tea leaves they may have nibbled on or simply brushed by.

In just 40 samples of dried teas and herbs, scientists discovered evidence of 1,200 distinct species of invertebrates.

"What really surprised me was the high diversity we detected," Henrik Krehenwinkel, an ecological geneticist at Trier University, told Shawna Williams of The Scientist. "We found in green tea up to 400 species of insects in a single tea bag."

Researchers discovered the tracks of 3,264 invertebrates from around the world, including predators, herbivores, detritivores, and parasites, in samples of professionally made teas and plants purchased at German grocery shops. Spiders, cockroaches, mites, flies, butterflies, mantids, and a variety of other insects left DNA traces.

The astonishing diversity, according to Krehenwinkel and colleagues, is due to the way the dried herbs (tea leaves, mint, and parsley) are processed: as they are ground up, DNA from all parts of the field where the crops are grown (likely including some stray whole bugs and their eggs) is preserved, mixed, and spread throughout the batch.

The resultant environmental DNA (eDNA) gives enough information for the researchers to establish where the plants were grown, as well as a glimpse of the invertebrate species in the area.

"Dried plant material appears excellently suited as a novel tool to monitor arthropods and arthropod–plant interactions, detect agricultural pests, and identify the geographical origin of imported plant material," the scientists concluded in their study.

However, they caution, "[w]hile our eDNA approach represents an important development for arthropod monitoring, it should be noted that it is not free of biases and will require further standardization in the future."

For example, scientists aren't sure if certain species might escape undiscovered since they leave less of a DNA trace on these plants, despite the fact that they're common in the ecosystem.

Regardless, this approach definitely delivers a lot of information that was previously unavailable to us. As a result, utilizing museum herbarium specimens, it might be used to ease environmental monitoring and potentially even assist expand species records back through time.

"Plant collections in museums, could they actually be useful to understand how insect communities have changed?" asks Krehenwinkel in The Scientist. "When insect decline studies were first published, a lot of people complained [that] there is no real long-term data." 

Krehenwinkel and his crew are now trying to figure out what's going on.

We all rely on insects and other invertebrates to help operate our life support system — our natural environment – thus these records should be available. Reading tea leaves might give us with critical information at a time when enormous environmental change is already occurring.