A unique group of cells pumps water into the kidneys to help extract moisture from the air.
Introduction
The red flour beetle (Tribolium castaneum) is a common pest in storage that feeds on stored grains, flour, cereals, pasta, biscuits, beans, and nuts. It is an extremely resilient creature, capable of surviving in harsh and dry environments due to its unique ability to extract liquids not only from grains and other food sources but also from the air. It opens its posterior when atmospheric humidity is relatively high and absorbs moisture through this opening, converting it into a liquid used to hydrate the rest of its body.
Absorption Mechanisms
Scientists have known about this ability for over a century, but biologists have finally begun to understand the underlying molecular mechanisms according to a research paper published in March in the Proceedings of the National Academies of Sciences. This discovery will aid future research on how to intervene in this hydration process to keep populations of the red flour beetle under control, as it is highly resistant to pesticides. It can also withstand higher levels of radiation than roaches.
Importance of Research
There are about 400,000 known species of beetles roaming the planet, although scientists believe there are over a million species. Each year, about 20 percent of the world’s grain stores are contaminated by red flour beetles, grain weevils, Colorado potato beetles, and confused flour beetles, especially in developing countries. Red flour beetles are a common model for scientific research on development and functional genomics. The entire genome was sequenced in 2008, and the beetle shares between 10,000 and 15,000 genes with the fruit fly (Drosophila), another insect used in genetic research. However, the beetle’s development cycle resembles that of other insects more closely.
Absorption Process
The rectums of most mammals and insects absorb any leftover nutrients and water from waste products in the body before defecation. But the rectum of the red flour beetle is a model of super efficiency in this regard. The beetle can generate very high saline concentrations in its kidneys, enabling it to extract all the water from its feces and recycle that moisture back into its body.
New Discovery
“The beetle can go through a complete life cycle without drinking liquid water,” said Kenneth P. Halberg, one of the authors and a biologist at the University of Copenhagen. “This is due to its modified rectum and closely attached kidneys, which form a highly specialized multi-organ system for extracting water from the food they eat and from the surrounding air. In fact, it occurs so effectively that the fecal samples we examined were completely dry with no trace of water.” The entire rectal structure is wrapped in kidney membrane.
Molecular Research
Halberg and his colleagues took scanning electron microscope images of the rectal structure of the beetle. They also took tissue samples and extracted ribonucleic acid (RNA) from red flour beetles raised in the lab, then used a new resource called BeetleAtlas to analyze gene expression, looking for any relevant genes.
Future Applications
A specific gene was expressed sixty times more in the rectum than any other gene. Ultimately, Halberg and his team identified a cluster of secondary cells between the beetle’s kidneys and circulatory system called leptophragmata. This discovery supports previous studies suggesting that these cells may be important, as they are the only cells that cross the renal membrane, facilitating critical transport for potassium chloride. In other words, the cells pump salt into the kidneys to extract moisture from feces or air.
Future Applications
The next step is to leverage these new insights to understand how to intervene in the beetle’s unique hydration process at the molecular level, possibly by designing molecules capable of doing so. These molecules could be integrated into more environmentally friendly pesticides targeting red flour beetles and similar pests without harming beneficial insects like bees.
Conclusion
“Now
We understand exactly which genes, cells, and molecules play a role when the beetle absorbs water through its rectum. This means that we suddenly have an understanding of how to disrupt these very effective processes by developing insecticides that target this function and thus kill the beetle,” said Halberg. “There are twenty times more biomass of insects on Earth than there is of humans. They play key roles in most food webs and have a significant impact on all ecosystems and human health. Therefore, we need to understand them better.”
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