Scientists reveal how beetles ‘drink’ through their anus

And, oddly enough, it’s relevant knowledge that can be used to combat global beetle infestations.

Over the past 500 million years, beetles have successfully spread across the planet. Today, even one in five animal species on earth is a beetle. Unfortunately, these insects are also among the pests that have a devastating impact on our food security. Every year, countless beetles eat thousands of tons of food. Food security in developing countries is particularly affected by the brown rice flour weevil and beetle, which are able to survive in extremely dry environments, including granaries. But how do they do this?

Not a drop of water
Beetles are therefore true champions for surviving in extremely dry environments. In fact, many species of beetles do not drink a drop of water throughout their lives. In a new study published in the journal Proceedings of the National Academy of Sciences, scientists have studied the molecular and physiological processes underlying this remarkable ability. And it turns out that beetles don’t actually drink with their mouths, but – sort of – with their butts.

Leptophragm cells
Researchers studied the internal organs of the brown rice flour beetle. It led to the discovery of a particular gene that is expressed in the rectum of the beetle. When the team dug deeper, they found a unique group of cells called leptophragm cells. And these cells in particular seem to play a crucial role in the absorption of water through the anus. “Leptophragmata cells are small cells found between the kidneys and the circulatory system,” says researcher Kenneth Halberg. “The kidneys of the beetle surround the large intestine. The leptophragm cells then pump the salts into the kidneys. This allows the beetle to extract water from the surrounding moist air through its anus and then transport it through the body. The gene we discovered is essential for this process, which is new knowledge for us.

In short, beetles can open their anus, extract water from moist air and turn it into liquid, which they then absorb into their bodies (see also the image above).

Extract water from food
But besides the fact that these clever insects “suck” water from the air with their rear end, they are also very passionate about extracting moisture from food. Even with cereals, which contain only 1 to 2% water, the beetle sees its chance. “The rectum and the kidneys are very close to each other,” says Halberg. “These organs form a system with other organs. This makes the beetle highly specialized in extracting water from food. In fact, they are so good at it that when we examined the feces, we found only dry feces with no trace of water.

Harmful beetles
Thanks to this study, scientists now better understand how beetles thrive in environments where few other animals can survive. But this new knowledge is also important for combating pesky beetle infestations. “We have shed new light on the molecular mechanisms that cause beetles to take up rectal water,” says Halberg. “Insects are particularly sensitive to changes in their water balance. This means that the new knowledge can be used to develop more targeted methods to control beetle species that destroy our food production, without killing other animals or harming people and nature.

food supply
The chestnut brown rice flour beetle, weevil and lesser flour beetle consume about 25 percent of the world’s food supply each year. To eliminate these insects from our food, approximately 100 billion dollars are spent each year in the world on pesticides. However, traditional pesticides are harmful to other living organisms and damage the environment. That’s why, says Halberg, it’s important to develop more specific, “eco-friendly” insecticides that target only pest-causing beetles, while bypassing more beneficial insects, such as bees. And a new and better understanding of beetle anatomy and physiology could be essential. “We now understand which genes and molecules play a role when the beetle takes in water through its anus,” concludes Halberg. “This means that we can now also design ways to disrupt these highly efficient processes. This can be done, for example, by developing insecticides that focus only on this function and thus kill the beetle.

At the same time, according to the researcher, it is important to deepen our knowledge of insects. Not only because there are so many of them, but also because they are an important link in almost every ecosystem on the planet. “They play a key role in most food webs and have a huge impact on virtually all ecosystems and human health,” Halberg points out. “So we need to understand them better.”