麻豆淫院

Insects use a wax layer on their bodies to prevent water loss. Furthermore, they use the layer for communication. Although the chemical composition of this layer has been extensively studied, researchers at Johannes Gutenberg University Mainz (JGU) in Germany and Universit茅 Paris Cit茅 in France have now, for the first time, turned to examining its physical properties, especially its phase behavior.

They focused on analyzing its viscosity by determining its resistance to flow.

"With regard to ants, we demonstrated that there is not only a gel phase and a liquid phase but also that the liquid phase exhibits two different levels of viscosity. One of them is rather viscous with a viscosity similar to that of honey, while the more fluid phase has a viscosity resembling that of olive oil," explained PD Dr. Florian Menzel of the Faculty of Biology at Mainz University.

"This is the reason why insects are able to maintain multiple functions of the wax layer simultaneously, even when they are exposed to fluctuating temperatures."

The research results have been in the Journal of the Royal Society Interface. The findings contribute to the understanding of the physical mechanisms that underlie the biological functions of insects' wax layer.

Conflicting requirements of the wax layer

There has been a drastic decline in insect populations in recent years, which is exacerbated by global warming. High temperatures are particularly dangerous for insects as their surface area is large in relation to their body volume, increasing the risk of desiccation. Heat exposure can thus cause excessive loss of water through their chitin cuticle.

The wax layer, which consists of cuticular hydrocarbons (CHCs), covers the chitin and forms a barrier through which water molecules can hardly diffuse. The higher its viscosity, the more waterproof it becomes.

However, the CHCs also provide communication signals that are detected by other ants and make sure, for example, that nestmates recognize each other and that workers of a colony divide up the different tasks in the nest.

To ensure the effectiveness of this chemical communication between the insects, the wax layer needs to have a low viscosity so that the signals can be easily perceived.

Complex phase behavior provides for viscosity requirements

The researchers were interested in how the viscosity of the protective layer differed with temperature. To this end, they exposed ants to various temperatures for several weeks and then analyzed the effects on their wax layer. They found that its viscosity decreased with increasing temperatures like in all semifluids鈥攎uch like honey becoming more liquid when heated.

The team discovered another interesting effect on examination of the wax layer of ants that had been kept at different acclimatization temperatures.

"In certain wax layers, there was an effect that was actually the opposite," said Selina Huthmacher of Mainz University.

"The viscosity of the wax layer of ants that were living at a temperature of 28 degrees Celsius was greater and less fluid than the layer of ants kept at a temperature of 20 degrees Celsius."

Of course, the higher the temperature, the greater the risk of water loss. As a result, ants need to protect themselves more effectively against desiccation with the help of a more viscous protective layer.

"This means that ants actively respond to natural changes in viscosity by altering the chemical composition of the wax layer and thus adapting its fluidity to current needs," explained Menzel.

The researchers also looked at how changes to either acclimatization temperature or measurement temperature impacted on viscosity. The results were particularly interesting when both acclimatization temperature and measurement temperature were the same.

If the ants were kept at a temperature of 28 degrees Celsius and the wax layer was measured at 28 degrees Celsius, the viscosity was equivalent to that of a layer from ants kept at 20 degrees Celsius and measured at 20 degrees Celsius, indicating that viscosity is the main parameter determining the function of the layer of CHCs.

"This complex phase behavior is very fascinating," concluded Huthmacher. "It is the reason why the wax layer of insects can serve to prevent dehydration and for communication at one and the same time, although the two functions have diametrically opposed requirements."