Scientists of the Biological faculty of Moscow State University studied how the relative sizes of insect organs change in the process of miniaturization-the decrease in the size of the body of insects during evolution. The performed work showed that the minimum attainable sizes of insects are limited by the size of the reproductive system and the nervous system. The principles and regularities of miniaturization, which scientists identified in animals, can be used in biotechnology and robotics in the future.
Miniaturization, or reduction in body size - is one of the main directions in the evolution of insects, as a result of which they become the size of single-celled organisms. Biologists have analyzed the large amount of data they have received over the last ten years of studying the structures of tiny insects.
Some of the smallest insects are the beetles and the hymenoptera mimarids. Their size is a fraction of a millimeter, and it is very difficult to see them with the naked eye. These insects appeared hundreds of millions of years ago, all this time they evolved, and this process continues. Micro-insects surround people almost everywhere: in urban areas, parks, mountains and forests. They are some in Moscow, although there are more of them in the southern latitudes and tropics. These insects have specific wings, not plates, as, for example, in dragonflies, but a vein with bristles along the edges, similar to a feather.
The main idea of the study was to assess how different insect organs suffer from changes in body size and what happens to the construction of organs when insect body size decreases from one centimeter to a tenth of a millimeter in order to understand what remains in the insect's body and what is changing.
Scientists built 30 complete and 26 partial 3D computer reconstructions for 22 species of insects from 11 families belonging to five orders (bristle tails, hay-ons, thrips, coleopterans and hymenopterans). Insects of different sizes were studied: the volume of their bodies varied more than 150,000 times. The species varied from 2 cm to 0.22 mm. Thus, the largest of the studied insects was larger than the smallest one 100 times in size and 100,000 times in volume. Based on these models, biologists analyzed the relative volumes of insect organs.
It turned out that most of the systems of insect organs can be reduced many times, while maintaining proportions. Systems of organs retain organization, and some - even an invariable relative volume, despite multiple decreases in size. Even in the smallest insects with a decrease in body size, the relative volume of metabolic systems, tissues of the internal environment and tracheal system becomes smaller. In this case, the reproductive and nervous systems, when the body size decreases, show a multiple increase in the relative volume.
Apparently, it is these systems that limit the minimum body size of insects. When these results were compared to literary data on vertebrate animals, it was possible to show that at the same scale of body size changes, most vertebral organs change disproportionately. Thus, the design of insects better tolerates scaling, especially the reduction in body size.
In the future, researchers plan to expand the range of studied objects by attracting insects from different groups: columbol, ticks and other arthropods.