Natural technologies: six old news

Unaccidental Analogies In Soviet times, popular science magazines liked to promote bionics—the science of designing technical devices that use the principles of living organisms. Unfortunately, bionics did not produce the effect its enthusiasts hoped for. Time and again, “snooping nature’s secrets” on demand failed. The reason lies in the fundamental difference between the materials used by living organisms and technical devices, as well as in the fundamentally different technological approaches. The cases where living nature and technology employed similar solutions most often turned out not to be the result of “industrial espionage” but of independent development of designs that shared similar features. However, time does not stand still. The development of nanotechnologies and progress in materials science bring technical solutions somewhat closer to biological ones. An example is a discovery made at the University of Exeter, United Kingdom. It turned out that the light‑emitting structures on the wings of the African butterfly *Princeps nireus* are similar to those on ultra‑efficient light‑emitting diodes produced a few years ago at the Massachusetts Institute of Technology. Examining the butterfly’s wings, scientists found that they do not merely reflect sunlight but glow brightly, efficiently emitting in a specific direction. Detailed microscopic analysis showed that the blue scales on the wings are ingeniously constructed. They contain a natural pigment that absorbs the blue portion of the solar spectrum and fluoresces at a slightly longer wavelength. Beneath the pigment lies an efficiently reflecting structure known in optics as a distributed Bragg reflector. But that is not all! Above the pigment there is a porous coating pierced by almost regular cylindrical channels. Calculations showed that it possesses the properties of a photonic crystal tuned to the wavelength emitted by the pigment. The photonic crystal prevents light from scattering and being absorbed by the wings, acting as a miniature waveguide that markedly increases emission efficiency¹. Remarkably, engineers who designed ultra‑bright LEDs arrived at essentially the same construction containing Bragg reflectors and a photonic crystal. Moreover, the structure of the scales suggested to scientists that a good photonic crystal does not require extremely strict adherence to size and periodicity of the holes. Another example. Professor Luke Lee of the University of California, Berkeley, argues that robotics should use eyes built on a faceted principle (as in arthropods) rather than camera‑eyes (as in vertebrates or cephalopod mollusks). Perhaps the similarity of arthropods to robots is not accidental? Both have a fixed set of movements, rigidly programmed behavioral scripts, and hard coverings. An artificial ommatidium (elementary “eye”) consists of a lens and a waveguide that directs light to an electronic sensor. From such lenses it is easy to assemble any surface; one could even almost completely cover a sphere, providing a view in all directions. Such systems are especially good for recognizing the motion of fast objects moving from one ommatidium to another. Since this construction works excellently in a dragonfly, why not apply it, for example, to an autonomous spy robot? One could also make a small round tablet, swallow it, and watch oneself from the inside… [IMG_1] Note that from the point of view of bionics, relatively old animal groups are of greater interest. Their adaptations have been honed by millions of years of evolution. Probably the most interesting animals from an engineering perspective are those that have been refining solutions to a specific narrow task over a long period. It is then that constructions resembling the discs on the toes of the gecko *Toky* appear, whose minute hairs adhere to any surface irregularities (whether rough or polished), engaging in van‑der‑Waals inter‑atomic interactions. Perhaps specialists from the Max Planck Institute in Germany or the University of Manchester in the United Kingdom, intrigued by such an idea, will be able to replicate this effect. [IMG_2] Nevertheless, wonders can also be shown by representatives of newer groups (though also highly specialized). Do you know, for example, why a sperm whale has such a large head? It occupies up to one‑third of the whale’s body length and appears rectangular from the side because of a cavity above the upper jaw filled with a waxy substance—the spermaceti. In antiquity this substance was considered “whale sperm”³, hence the name. By the way, it was precisely because of the spermaceti that sperm whales were heavily hunted—it is an exceptionally suitable base for expensive perfumery, efficiently binding various aromatic molecules. That the spermaceti has nothing to do with lust has been known for a long time, but its true purpose became clear only recently. Terrestrial quadrupeds (including humans) can encounter difficulties when diving because of the air in the lungs. Before diving we take a deep breath. Air‑filled lungs give the body positive buoyancy that must be overcome during submersion. Yet as soon as one works intensively with the limbs and descends deeper, the situation changes. Considering that the pressure of a ten‑meter water column roughly equals one atmosphere, at that depth pressure doubles and lung volume halves. The body’s buoyancy becomes negative, pulling it further down—so now one must ascend, overcoming this effect. A sperm whale dives to two kilometres—it hunts giant squids there. Naturally, this requires a thoracic cage that can withstand a two‑hundred‑fold reduction in volume (human ribs would break under far smaller compression). Moreover, the whale’s dive and ascent are facilitated by the spermaceti cavity. This substance liquefies at body temperature and solidifies, substantially increasing its volume with a slight temperature drop. Before diving, the whale enhances blood flow to the spermaceti cavity. The spermaceti melts, the head’s volume decreases and the whale is drawn downward. The whale dives. When it is time to ascend, it cools the spermaceti (either by reducing circulation or by drawing “foreign” water into the nostrils). The spermaceti expands, increasing head volume and counteracting the crushing external pressure. With its head forward, the whale surges toward the surface, holding a weakening squid in its jaws… For bathyscaphes and submarines, buoyancy changes are linked to the consumption of certain substances—ballast discharge, release of kerosene from suspended tanks, use of compressed air to vent compartments. A sperm whale expends only the energy obtained by oxidizing the flesh of deep‑water squids with atmospheric oxygen that it draws at the surface. Engineers have plenty to work on!

However, time does not stand still. The development of nanotechnology and progress in materials science are bringing technical solutions somewhat closer to biological ones. An example is the discovery made at the University of Exeter, UK. It turned out that the light-emitting structures on the wings of the African butterfly *Princeps nireus* are similar to those in the energy-saving LEDs manufactured a few years ago at the Massachusetts Institute of Technology.

Examining the butterfly's wings, scientists found that they do not just reflect sunlight, but glow brightly, effectively emitting in a specific direction. Detailed microscopic analysis showed that the blue scales on the wings are extremely ingeniously arranged. They contain a natural pigment that absorbs the blue part of the solar spectrum and fluoresces at a slightly longer wavelength. Beneath the pigment is an effectively reflective structure known in optics as a distributed Bragg reflector.

But that's not all! Above the pigment is a porous coating, permeated with almost regular cylindrical channels. Calculations showed that it possesses the properties of a photonic crystal tuned to the wavelength emitted by the pigment. A photonic crystal prevents light from scattering and being absorbed by the wings, acting as a miniature waveguide that significantly increases radiation efficiency¹.

It is striking that engineers arrived at exactly the same structure, containing Bragg reflectors and a photonic crystal, when designing ultra-bright LEDs. Moreover, the structure of the scales suggested to scientists that for a good photonic crystal, it is not at all necessary to strictly adhere to the dimensions and periodic arrangement of the holes.

Another example. Professor Luke Lee of the University of California, Berkeley, believes that robotics would benefit more from using eyes made on the facetted principle (like in arthropods) rather than camera eyes (like in vertebrates or cephalopods). Perhaps the similarity between arthropods and robots is not accidental? Both have a fixed set of movements, rigidly defined behavioral programs, and hard exoskeletons. An artificial model of an ommatidium (an elementary "eye") consists of a lens and a waveguide that redirects light to an electronic sensor. Such lenses can easily form any surface; one can even cover a sphere almost completely with them, providing 360-degree vision. Such systems are particularly good for detecting the movement of fast objects transitioning from one ommatidium to another. Since such a design works excellently in the case of a dragonfly, why wouldn't it be suitable, for example, for an autonomous spy robot? And one could also make a small round pill, then swallow it and look at oneself from the inside...

Note that from the perspective of bionics, relatively old groups of animals are of greater interest. Their adaptations have been refined by millions of years of evolution. Probably, the most interesting animals from an engineering point of view are those that have been improving for a long time in solving a specific narrow task. This is when structures like the discs on the feet of the gecko *toki* appear, tiny bristles that adhere to any surface irregularities (whether rough or polished), entering into interatomic van der Waals interaction with them. Perhaps specialists from the Max Planck Institute in Germany or the University of Manchester in the UK, interested in such an idea, will succeed in copying a similar effect.

However, representatives of new groups (though also very specialized) can also demonstrate wonders. Do you know, for example, why the sperm whale has such a large head? It occupies up to a third of the sperm whale's body length and appears rectangular from the side due to a cavity filled with a waxy substance – spermaceti – located above the upper jaw. In ancient times, this substance was considered whale sperm³, hence the name. By the way, sperm whales were intensively hunted precisely for spermaceti – it is an extremely effective component for expensive perfumes, efficiently binding various aromatic molecules. That spermaceti has nothing to do with lust has long been known, and its true purpose became clear only recently.

In terrestrial quadrupeds (including humans), diving can present difficulties due to the presence of air in the lungs. After all, before diving, we take a deep breath. Lungs filled with air give the body positive buoyancy, which must be overcome during the dive. But as soon as you start working your limbs intensely and descend deeper, the situation changes. Considering that the pressure of ten meters of water column is approximately equal to atmospheric pressure, at this depth the pressure doubles, and the volume of the lungs halves. The body's buoyancy becomes negative, and it is pulled further down – but here you need to ascend, overcoming this effect.

The sperm whale dives to two kilometers – it hunts giant squid there. Obviously, for this, it needs a rib cage that can withstand a two-hundred-fold reduction in volume (human ribs would start to break at much less compression). Furthermore, the whale's diving and ascent are facilitated by the spermaceti cavity. This substance transitions to a liquid state at body temperature and solidifies, significantly increasing its volume upon slight cooling. Before diving, the sperm whale increases blood supply to the spermaceti cavity. The spermaceti melts, the whale's head decreases in volume, and it begins to pull itself down. The sperm whale dives. When it's time to ascend, it cools the spermaceti (either by reducing blood flow or by taking in "sea" water into its nostrils). The spermaceti expands and increases the head's volume, overcoming the tremendous external pressure. Headfirst, the sperm whale rises to the surface, holding the weakened squid in its jaws...

For bathyscaphes and submarines, changes in buoyancy are associated with the consumption of certain substances – dropping ballast, releasing kerosene from auxiliary tanks, expending compressed air to purge tanks. The sperm whale expends only the energy it obtains by oxidizing the meat of squid caught at depth with oxygen from the air it takes in at the surface.

Engineers have something to work on!

1 This is needed so that, fluttering under the canopy of a dense African forest, members of one species can recognize each other. Back to text 2 Diameter 0.2 µm. Back to textImagine how the male looks! And all that wealth struck him on the head! Back to the text Ode to the Parasite Acknowledging the complexity of nature in words, we retain a tendency toward black‑and‑white thinking, dividing species into useful and harmful, good and bad, attractive and repulsive. Reality, as always, turns out to be more complicated. Here are just a few recent news items related to interspecific relationships. The Hamburg firm Ovamed is developing a new remedy for allergy and other autoimmune diseases. It is a liquid containing larvae of Trichuris suis, a roundworm that parasitizes pigs. It is assumed that such an attractive preparation could help combat a multitude of ailments, from chronic rhinitis to asthma or colitis. The point is that with the defeat of helminths our immune system loses its natural targets and begins to react to false signals, turning it against its own tissues. This self‑directed battle becomes the cause of many fashionable diseases of our time. It is planned that during the two weeks that pig worms would reside in the human intestine, they would offer the immune system a more suitable target. Parasites also affect salmon, in particular Atlantic salmon and chum. These anadromous fish spawn in rivers, but as fry they move to the sea, where they live until reaching sexual maturity. Mature fish return to rivers, release eggs and die. However, one factor may halt this self‑destruction mechanism. It is the larvae of the European pearl mussel, once common and now disappearing bivalve, whose life cycle includes parasitism on fish gills. Settling on salmon gills, pearl mussel larvae release substances that block the “clock” of death and even enhance the host’s resistance to fungal infections. The latter is not superfluous, and here is why. An authoritative panel of specialists convened in Washington identified the cause responsible for the sharp decline in amphibian numbers worldwide. It is Batrachochytrium dendrobatidis, a fungus from the chytridiomycete group that attacks their skin. Until recently this fungus was unknown, and now, spreading worldwide with human assistance, it threatens almost a third of existing amphibian species. The relationship of this parasite with its hosts has a short history, which is why its spread is so destructive. In an evolutionary perspective, the invasive fungus must either develop mechanisms that promote the preservation of its resources (amphibian populations) or disappear (perhaps together with its hosts). A few more examples of unexpected links between different species. The existence of the black rhinoceros is threatened by Chromolaena odorata – a South American weed spreading in Africa. In the new location this species proved highly viable. Its impact on rhinos is simple: the invader displaces native grass species and forces rhinos to abandon lands that become unsuitable for them. The highest diversity of woody plants is found in tropical rainforests. In dense forest, trees of the same species are separated by tens and hundreds of meters. That is why patches completely overgrown by a single species (Duroia hirsuta) have been called “devil’s gardens”. Researchers from Stanford University have shown that these gardens “grow” the ant Myrmelachista schumanni. Ants living in the stems of the named tree species eliminate seedlings of all other species, using formic acid as a herbicide. We are gradually learning to harness the benefits of interspecific interactions. Thus, they can be applied for plant protection. In addition to many methods of crop protection (treating with pesticides; making plants toxic or repellent to pests; releasing natural enemies of pests, etc.) another has been added. A British‑Dutch team of genetic engineers inserted into the model plant Arabidopsis thaliana a gene that attracts predatory mites (Phytoseiulus persimilis), which protect the plant from other harmful mites. This solution is novel only for humans. In the plant world this method is widespread. But to use such solutions, we need to look at the world around us much more attentively than we are accustomed to. Virtual Reality in a Cuckoo‑like Manner The energetic costs of offspring production in birds, as in many other animals (humans, for example), can be divided into two parts. The first is related to the physiological losses of the mother (in birds, egg development; in humans – gestation). The second group of costs is associated with meeting the needs of growing offspring (in birds – feeding chicks; in humans – upbringing and meeting various children’s needs). The more complex the organism and the more intensive the parental care, the larger the proportion of the second‑group costs. Curiously, however, they can in principle be avoided. In folk terminology this strategy is often called “cuckoo‑like”, and ornithologists refer to it as brood parasitism. The cuckoo lays its eggs in the nests of other bird species. The cuckoo chick develops faster than the host’s own young, and as soon as it hatches it ejects the other eggs and chicks from the nest. It then merely redirects the foster parents’ care onto itself, forcing them to expend effort feeding a single oversized “monster” (usually the cuckoo is much larger than the species it parasitizes). Have you ever noticed how a child’s need for care or the innate ability of children to coo and “make eyes” touches the soul, attracting attention? We are programmed to care for children, and they know which buttons to press when necessary. The psyche of foster cuckoo parents is simpler than ours, making them more manipulable. The visual cue that motivates feeding birds is the widely opened begging mouth of the chick, often colored yellow or red, or even marked with contrasting spots. The auditory cue is the demanding peep of the begging chick. The European cuckoo uses the auditory channel to manipulate foster parents. Loud cries of the single chick make the parents tirelessly thrust food into its insatiable mouth. But the drawback of a loud cry is that it attracts predators – martens and weasels can destroy half of all nests. Japanese ornithologists published in Science results of a study of a common cuckoo species in their country. The chicks of this species have spots on their wings resembling the open mouths of foster chicks. The begging chick trembles its whole body, and the “mouths” on its wings flutter like the heads of hungry infants on thin necks. In the dim light of the nest this picture convinces the parents of the doomed brood and motivates them to care for the nest parasite. Thus, visual mimicry allows a reduction in the loudness of cries that pose a danger to the very chick being presented. Set aside anthropomorphic assessments: the cuckoo’s strategy can be called cunning only metaphorically. But how can one not admire its perfection? Information War with Bacteria Recently a conceptually new idea for combating pathogenic bacteria has spread. As simple as these organisms are, information exchange among them plays a significant role in infection development. It turns out that many disease agents can choose one of two strategies. The first is that the bacterium remains in a “dormant” state, not exploiting the host but preserving its life thanks to low activity of the host’s immune system. The second consists of attacking the host organism and (in case of “victory”) proliferating intensively at its expense. Switching from the first to the second strategy can be triggered, for example, by a sharp weakening of the host. While the host is healthy, an attack by a small number of bacteria will lead to their destruction. However, if there are many bacteria, the defensive systems opposing them may simply be overwhelmed. Thus bacteria need to exchange information about the size of the “pack” and commence attack only after reaching a critical density. This is how agents of various diseases behave, including cholera, salmonellosis, tuberculosis or caries. A convenient model for studying chemical communication turned out to be the bacteria that cause bioluminescence in certain squid species: they begin to glow blue only after the attackers reach a critical density. If the transition of bacteria to an active state results from information exchange among them, then disrupting this exchange can keep pathogens from attacking. Substances studied at the University of New South Wales (Australia) – furanones – may be useful in implementing this idea. They are extracted from the Australian red alga Delisea pulchra. So far a suppressive effect of furanones has been recorded on luminous squid bacteria (which has little practical significance) and on cholera pathogens (which is much more important). Moreover, using substances that “pacify” bacteria is far more promising than waging war on them with antibiotics. If bacterial growth is restrained by an antibiotic, even the offspring of a single resistant mutant can capture all available resources. And for bacterial communication to work successfully in the presence of pacifying substances, a sufficient number of resistant individuals must be present. What’s the point of calling for an attack if no one hears you? 3D‑Genome: How Does It Work? The European Union allocated €2.2 million to the international 3DGENOME program. It is carried out by a consortium of seven European partners coordinated from the Swammerdam Institute at the University of Amsterdam. The program’s task is to determine the three‑dimensional structure (conformation) of DNA in the cell nucleus. The study will employ the latest microscopy methods combined with image‑processing software systems that allow reconstruction of the DNA super‑molecule structure. Work will be conducted on cells of humans, mice and Drosophila (researchers consider that, from their point of view, these cells do not differ fundamentally). [IMG_3] The length of DNA molecules contained in a human cell nucleus reaches 2 m. For comparison: a thread of the same compactness would be twenty‑kilometre long and could fit into a tennis ball! Moreover, this “thread” is not merely packed but works intensively: complex enzymatic systems monitor DNA status and read information from its active regions. DNA compaction occurs on several levels; interactions between various DNA segments and different proteins are crucial. 3DGENOME is one step toward understanding the mechanisms that regulate cell and organism development. The previous step was the widely publicized Human Genome Project. Although it concluded successfully (the majority of human DNA sequences were read), optimists were disappointed. A wealth of valuable and interesting facts was obtained, yet how the genome works as a whole remained unclear. Unfortunately, it is still not understood how to explain the entire structural‑functional complexity of the human body and psyche with 35 thousand genes constituting about 2 % of DNA. The link between gene activity and cellular specialization is an extremely complex research problem. It is now clear that one of the main ways of regulating gene activity is precisely the alteration of DNA conformation. When studying it, the DNA molecule must be viewed not as a collection of separate regulatory units separated by “junk”, but as a unified whole with many degrees of freedom. Nevertheless, the question remains open: will our capacity to interpret ultra‑complex data arrays be sufficient to understand the developmental regulation mechanism after this project is completed? Ground Squirrel with an IR Port At the University of Davis (California) the first transmission of information between two animal species via infrared radiation was recorded. Many nocturnal reptiles possess special organs for detecting the thermal radiation of prey – depressions on the snout surface covered with a thin membrane. Thus, pit‑viper snakes (including pit vipers, rattlesnakes, etc.), whose organs are most developed, can hunt in total darkness or with their eyes covered. Hiding from visually oriented predators, prey can camouflage against the background; concealing thermal radiation is practically impossible. Even when hunting by day, snakes equipped with thermolocators obtain a substantial portion of environmental and prey information through these organs. [IMG_4] In California rattlesnakes prefer to hunt young ground squirrels, as adult individuals are too evasive and aggressive as prey. When encountering a rattlesnake, ground squirrels boldly attack it. Remarkably, the rodents increase thermal emission from their tails (spreading the fur and enhancing blood flow). This signal is perceived by the snake, which likely shifts from hunting behaviour to a defensive one. It cannot be excluded that the “hot” tail becomes a false target for the rattlesnake, which will strike there first. This squirrel response is not automatic but is specifically linked to this type of predator: defending against snakes lacking thermolocators, the rodents do not waste energy heating their tails. This is logical overall: each species should be addressed in the language it can understand. D. Shabanov, Andreev G. Accidental Analogies // Kompyutera, M., 2005. – No. 44 (616) D. Shabanov. Ode to the Parasite // Kompyutera, M., 2005. – No. 39 (611) D. Shabanov. Virtual Reality in a Cuckoo‑like Manner // Kompyutera, M., 2005. – No. 19 (591) D. Shabanov. Information War with Bacteria // Kompyutera, M., 2004. – No. 48 (572) D. Shabanov. 3D‑Genome: How Does It Work? // Kompyutera, M., 2004. – No. 26–27 (550–551). – p. 11 D. Shabanov. Ground Squirrel with an IR Port // Kompyutera, M., 2004. – No. 25 (549). – p. 14