Beetles excel at surviving in harsh conditions of aridity. They can suck water out of the air with their back ends, which contributes to their feature. Just how is clarified in a recent collaborative study conducted by scientists from the Universities of Edinburgh and Copenhagen.
The understanding could potentially be applied for more precise and delicate control of common pests like the red flour beetle and grain weevil, in addition to helping to explain how beetles thrive in conditions where few other species can survive.
Pest insects consume thousands of tons of food each year all around the world. Animal species that have specialized in surviving in extremely dry settings, including granaries for thousands of years, such the grain weevil and red flour beetle, have a particularly negative impact on food security in underdeveloped countries.
In the new study, which is published in Proceedings of the National Academy of Sciences , researchers at the University of Copenhagen’s Department of Biology investigated the molecular and physiological processes underlying the ability of beetles to survive their entire lives without drinking any liquid water whatsoever. One of the secrets of this characteristic is found in their rear ends.
In fact, beetles have the ability to open their rectums, allowing them to absorb liquid by turning water from wet air into water. Throughout scientific communities all across the world, this innovative method of drinking water has been known for more than a century, but it has never been properly explained until now.
“We have shed new light on the molecular mechanisms that allow beetles to absorb water rectally. Insects are particularly sensitive to changes in their water balance. As such, this knowledge can be used to develop more targeted methods to combat beetle species which destroy our food production, without killing other animals or harming humans and nature,” says Associate Professor Kenneth Veland Halberg of the Department of Biology, who led the research.
Now we understand exactly which genes, cells and molecules are at play in the beetle when it absorbs water in its rectum. This means that we suddenly have a grip on how to disrupt these very efficient processes by for example developing insecticides that target this function and in doing so, kill the beetle.
Professor Kenneth Veland Halberg
Bone dry stool testifies to effective fluid extraction
To discover more about red flour beetles’ capacity to absorb water through the rectum, scientists looked into their internal anatomy. Since red flour beetles are employed as “model organisms,” their biology is comparable to that of other beetles, and they are provided with equipment that make them simple to work with.
In this case, the researchers discovered a gene that, compared to the rest of the animal, is expressed sixty times more in the rectum of the beetle. This led them to a unique group of cells known as leptophragmata cells. Upon closer inspection, they could see that these cells play a crucial role when the beetle absorbs water through its rear end.
“Leptophragmata cells are tiny cells situated like windows between the beetle’s kidneys and the insect circulatory system, or blood. 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. The gene we have discovered is essential to this process, which is new knowledge for us,” explains Kenneth Veland Halberg.
Besides being able to suck water out of the air, beetles are also extremely effective at extracting liquid from food. Even dry grain, which may consist of 1-2 percent water, can contribute to a beetle’s fluid balance.
“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. In fact, it happens so effectively that the stool samples we have examined were completely dry and without any trace of water,” explains Halberg.
As much as 25 percent global food production is lost
Over the past 500 million years, beetles have successfully spread across the planet. Today, one in five animal species on Earth is a beetle. Unfortunately, beetles are also among the pests that have a devastating impact on our food security.
The red flour beetle, grain weevil, confused flour beetle, Colorado potato beetle and other types of beetles make their way into up to 25 percent of the global food supply every year.
We use approximately $100 billion in pesticides worldwide every year to keep insects out of our food. However, traditional pesticides harm other living organisms and destroy the environment.
Halberg contends that it is crucial to create more focused and “eco-friendly” insecticides that only target insect pests and ignore more advantageous insects like bees. A fresh and improved understanding of the anatomy and physiology of beetles could be crucial in this situation.
“Now we understand exactly which genes, cells and molecules are at play in the beetle when it absorbs water in its rectum. This means that we suddenly have a grip on how to disrupt these very efficient processes by for example developing insecticides that target this function and in doing so, kill the beetle,” says Halberg.
“There is twenty times as much insect biomass on Earth than that of humans. They play key roles in most food webs have a huge impact on virtually all ecosystems and on human health. So, we need to understand them better,” concludes the researcher.
