Many beetle species never need to drink once throughout their lives, even if they live in deserts or eat dry food. The solution to the riddle is in her backside.
Beetles are real artists of adaptation, especially when it comes to drought. For example, storage pests such as the grain weevil, flour beetle or red flour beetle can live in dry grain and flour and feed on these supplies without dying of thirst. This is possible because they not only have a very water-saving metabolism – they can also absorb moisture directly from the air. However, this does not happen via the body surface or its mouth opening, but with its rear end – the anus.
Researchers led by Kenneth Veland Halberg from the University of Copenhagen have explained how the beetles use their rectum to absorb water. “We shed new light on the molecular mechanism that allows the beetles to absorb water rectally,” explains Halberg. With the help of genetic analyzes and histological studies of the red flour beetle (Tribolium castaneum), they discovered that these insects have a very special system in their rectum for this purpose.
“Your rectum and your closely surrounding kidneys combine to form a multi-organ system that is highly specialized for extracting water from the food you eat and from the air around you,” explains Halberg. A group of special cells that the researchers discovered in the beetle’s rectum plays a decisive role in this: “The leptophragmata cells lie between the beetle’s kidneys, which surround its rectum, and the animals’ circulatory system,” says the scientist. “They pump salts into the kidneys so they can absorb the water from the humidity.”
This stained electron micrograph shows the rectum of a flour beetle. The insect’s droppings, which are dust-dry due to the effective water absorption, are colored magenta, the tissue of the anus can be seen in grey. The Malpighian vessels, which function as kidneys and are protuberances of the intestine, have been colored purple here. They are also responsible for the newly discovered Leptophragmata cells.