Beetles Hydrate by Drinking Through Their Butt Holes. Here’s How They Do It : ScienceAlert

A new study has shed light on how insects have evolved their water-recycling and water-conservation mechanisms. Kenneth Veland Halberg and his colleagues from the University of Copenhagen worked with researchers from the Universities of Edinburgh and Glasgow in the UK to identify a protein that controls the process. By looking in BeetleAtlas for genes that were expressed more in the rectum, the researchers were able to focus on one in particular, called NHA1. The red flour beetle is often used to study insects because its biology is similar to other insects, its genome is well-sequenced, and it is easily accessible as an everyday kitchen pest. Thousands of tons of food are lost every year due to insect pests, and the impact on developing countries’ food security is particularly severe.

“A beetle can go through an entire life cycle without drinking liquid water. This is because of their modified rectum and closely applied kidneys, which together make a multi-organ system that is highly specialized in extracting water from the food that they eat and from the air around them,” explains biologist Kenneth Veland Halberg from the University of Copenhagen in Denmark. The researchers used RNA sequencing to compile an atlas, called – you guessed it – BeetleAtlas, detailing the developmental stages of T. castaneum so they could compare gene expression between different organs and at different times in their lives. The team showed that NHA1 expression increased in beetle butts when the animals were exposed to drier conditions, allowing them to absorb more water from the environment and their feces.

The red flour beetle (Tribolium castaneum) is often used to study insects because its biology is similar to that of other insects, its genome is well-sequenced, and it is easily accessible as an everyday kitchen pest. With their specialized rectal ability, beetles can survive in the driest regions on Earth, including the flour and grains in your pantry. They can also reabsorb water from their poop, and their butts are surprisingly proficient at wringing moisture out of it, too. Microscopic cross-section of the beetle’s hindgut shows the dry stool in magenta, surrounded by the intestine in gray. The excretory tube of the beetle is shown in purple.

“As the beetle’s kidneys encircle its hindgut, the leptophragmata cells function by pumping salts into the kidneys so that they are able to harvest water from moist air through their rectums and from here into their bodies,” Halberg explains. What’s more, when NHA1 functionality was turned off in the lab, the beetles lost more water through excretion, making it harder for them to survive in dry conditions and demonstrating that NHA1 is important for the transport of water from their rectums to their body. Insects are particularly sensitive to changes in their water balance, says Halberg. As such, this knowledge can be used to develop more targeted methods to combat beetle species which destroy food production, without killing other animals or harming humans and nature. To facilitate future studies, the authors have made BeetleAtlas available to other scientists. Expression in over 16,500 genes in the Tribolium genome can now be easily compared thanks to their RNA sequencing that spans embryonic, larval, and adult stages.



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