Researchers discover how beetles use their bottoms to stay hydrated.

Beetles excel at maintaining their existence in extremely dry environments. Their ability to extract water from the air with their rear ends contributes to this property in part. This is demonstrated in detail in a recent joint study by researchers from the University of Edinburgh and the University of Copenhagen. The knowledge could eventually be used for more precise and delicate control of global pests like the grain weevil and red flour beetle, in addition to assisting in the explanation of how beetles thrive in environments where few other animals are able to survive.

Every year, insects and other pests consume thousands of tons of food worldwide. Animals like the grain weevil and the red flour beetle, which have specialized in surviving in extremely dry environments like granaries for thousands of years, have a particularly negative impact on food security in developing nations.

Researchers from the Department of Biology at the University of Copenhagen looked into the molecular and physiological processes that allow beetles to live their entire lives without drinking any liquid water in the new study, which was published in the Proceedings of the National Academy of Sciences. Their rear ends conceal one of this characteristic’s secrets.

“We discovered novel chemical processes that allow beetles to take water rectally. Insects are especially sensitive to changes in water balance. As a result, this knowledge can be used to design more focused strategies of combating beetle species that devastate our food supply while without killing other animals or harming humans or nature.”

Associate Professor Kenneth Veland Halberg of the Department of Biology,

In fact, beetles have the ability to open their rectums and absorb water from moist air by converting it into a liquid. In scientific circles all over the world, this novel method of drinking water has been known for more than a century, but it has never been fully understood until now.

“We have provided fresh insight into the molecular mechanisms that enable beetles to rectally absorb water. Changes in the insect’s water balance have a significant impact on their sensitivity. According to Associate Professor Kenneth Veland Halberg of the Department of Biology, who led the research, “this knowledge can be used to develop more targeted methods to combat beetle species that destroy our food production without killing other animals or harming humans or nature.”

Credit: Kenneth Halberg

Illustration of the inside beetles and how they extract water from the air Credit: Kenneth Halberg

Bone-dry stools demonstrate efficient fluid extraction.

The researchers investigated the internal organs of red flour beetles to gain a deeper understanding of the rectum’s capacity for water absorption. Red flour beetles are used as “model organisms,” which means that their biology is like that of other beetles and that they have tools that make them easy to work with.

In this case, the researchers discovered a gene that is expressed sixty times more in the beetle’s rectum than anywhere else in the animal. This brought them to leptophragmata cells, a distinct class of cells. After looking into it further, they could see that these cells assume a pivotal role when the insect retains water through its backside.

“Leptophragmata cells are small cells that sit between the beetle’s kidneys and the insect’s blood, or circulatory system, like windows.” The leptophragmata cells function by pumping salts into the kidneys as the beetle’s kidneys encircle its hindgut. This allows the kidneys to harvest water from moist air through their rectums and into their bodies. ” Kenneth Veland Halberg explains that what we have discovered is that the gene is necessary for this process, which is new information for us.”

Beetles are extremely effective at removing liquid from food, in addition to sucking water from the air. A beetle’s fluid balance can be influenced by anything, even dry grain, which may contain between one and two percent water.

“A beetle’s life cycle can be completed without consuming liquid water. This is due to their modified rectum and closely placed kidneys, which combine to form a multi-organ system that is highly specialized in the extraction of water from their food and the air around them. In point of fact, it works so well that the stools we looked at were completely dry and devoid of any water,” says Halberg.

Credit: Kenneth Halberg

Animals that have specialized in surviving in extremely dry environments, including granaries, for thousands of years, such as the grain weevil and red flour beetle, have a particularly negative impact on food security in developing nations. Credit: Kenneth Halberg Beetles have successfully spread across the globe over the past 500 million years, accounting for up to 25% of the world’s food production. Beetles now account for one in five animal species on Earth. Sadly, beetles are also one of the pests that have a devastating effect on our ability to obtain food. Each year, beetles like the red flour beetle, grain weevil, confused flour beetle, Colorado potato beetle, and others enter up to 25% of the world’s food supply.

Every year, we use approximately $100 billion worth of pesticides to keep insects out of our food. On the other hand, conventional pesticides harm other organisms and the environment.

As a result, Halberg asserts, it is crucial to develop insecticides that are more specific and “eco-friendly,” focusing solely on insect pests and omitting more beneficial insects like bees. A new and improved understanding of beetle anatomy and physiology could be crucial in this situation.

We now know precisely which genes, cells, and molecules are involved in the beetle’s rectum water absorption. This indicates that we now have a firm grasp on how to disrupt these highly effective processes, such as by developing insecticides that target this function and kill the beetle, according to Halberg.

“Insect biomass is twenty times greater than human biomass on Earth. They play important roles in the majority of food webs, which have a big effect on nearly every ecosystem and human health. Therefore, we must improve our comprehension of them,” the researcher concludes.

More information: Muhammad T. Naseem et al, NHA1 is a cation/proton antiporter essential for the water-conserving functions of the rectal complex in Tribolium castaneum, Proceedings of the National Academy of Sciences (2023). DOI: 10.1073/pnas.2217084120

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