secret stash

Look: Beetles carry bacteria in little pockets on their back for an important reason

One heck of a family heirloom.

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Imagine if your family’s most treasured heirloom was a bunch of bacteria.

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That’s the case for Lagria beetles, who have a symbiotic relationship with the bacteria that live in their bodies.

When the beetles lay eggs, they pass several bacterial strains along to their young — and for good reason.

One strain of Burkholderia, which is dominant in Lagria beetles, helps shield the larvae from deadly fungal infestations.

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And in return, the bacteria has somewhere to live.

Colonies are not able to survive on their own very long without a host.

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Scientists were puzzled as to how the bugs hold onto bacteria colonies as they undergo a complete metamorphosis on the way to adulthood.

RS Ranke

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It turns out female Lagria have a clever method for stashing away bacteria as their bodies shapeshift, write researchers this week in the journal Frontiers in Physiology.

Janke et al, Frontiers in Physiology

To investigate, they injected small fluorescent beads the size of bacteria into beetles undergoing metamorphosis.

Then, they scanned and dissected the bugs to see where the beads went.

Janke et al, Frontiers in Physiology

During the transformation, female beetles appeared to store bacteria in little pockets along their backs.

This micro CT scan shows the location of the pockets (red) in a beetle undergoing metamorphosis.

LV Flórez, RS Janke, S Moog, B Weiss, M Kaltenpoth

Then, as they emerge from their cocoon as fully-fledged adults, the bacteria is scraped down to the end of their thorax where they can coat freshly-laid eggs in a protective goo.

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Male beetles, on the other hand, don’t appear to hold onto much of the bacteria, since they don’t lay eggs.

And since the bacteria’s main goal is to keep proliferating, it’s most beneficial for colonies to stick near the reproductive organs of the female beetles.

LV Flórez, RS Janke, S Moog, B Weiss, M Kaltenpoth

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That way, the cycle can continue with each new generation of Lagria beetles carrying their family heirloom to the next.