The teeth of a tiny mollusk (Patella vulgata), which is a species of sea snails, have been found to be some of the strongest biomaterials in the world. Also known as limpets, these mollusks are a very small crustacean, often around 0.05-2 cm in size with a large cone shell and possess an incredibly complex system of teeth that dazzles the mind.

Research has revealed that the tensile strength of the sea snail’s teeth is higher than that of spider silk and is comparable to only the strongest commercial carbon fibers. It was found that the teeth of sea snails scraping algae off of rocks showed a tensile strength between 3 and 6.5 GPa (gigapascals). Spider silk roughly reaches a tensile strength of about only 1.3 Gpa. Scientists say that the snail’s teeth can even withstand the pressure that turns carbon into diamonds. Studies have determined that, to our current knowledge, there is no other material of this size (roughly 100 μm micrometers) with as much strength and durability.

This exceptional durability has led scientists to do research on the structure and functioning of these teeth, and the studies showed fascinating results.

The role of teeth in nutrition

Sea snails have a special tongue, called a radula, which they use to scrape off food from rocks. The most important feature of the radula is that it contains more than 100 rows of iron-mineral teeth. However, those used for food intake consist of only 10 rows on the outermost part of the teeth. During eating, a tremendous mechanism operates: the teeth are constantly repositioned according to their conditions of maturation and wear. Worn teeth are replaced by newly matured teeth over the course of 12 to 48 hours to ensure that fresh, sharp teeth are used instead of dulled ones.

This wonderful displacement system operates in a similar way to the movement mechanism on a conveyor belt where the teeth begin to grow primarily in the posterior part of the radula. Meanwhile, they are strengthened and matured by iron mineralization. When this mineralization is complete, they are moved towards the front of the radula. In this way, completely matured teeth are permanently retained at the far-front scraping area. During the scraping process, the matured teeth wear out at a rate equal to the growth rate. In the meantime, a new set of teeth begins to grow. By means of this magnificent cycle, new teeth are constantly created and matured so that there are no disruptions in nutrition.

Biomineralization

The structure of the sea snail’s teeth is also a masterpiece of material science. The dazzling durability of its structure provides optimum strength when scraping food off of rock surfaces.

Although the exact process of biomineralization of the teeth is not known, it is believed that it involves reactions of dissolution and re-precipitation. When the non-mineralized matrix is examined, well-arranged and densely packed chitin fibers are observed that are only a few nanometers apart. The matrix is a structure which keeps the reinforcing material together in layers that are composed of different materials. This organic matrix serves as a framework for crystallization in the structure of the teeth. In the mineralization system, the basic macromolecule α-chitin component is created first. The first mineral that then precipitates is the “goethite,” i.e. the aqueous iron-oxide mineral, which crystallizes parallel to the chitin fibers. These crystals are nucleated on the chitin fibers and formed between them by pushing and pulling the fibers. This way, crystals placed in order cause biomineralization of the structure.

It was found that 80% of the overall volume of the structure is composed of these crystals. The gap between the crystals and the chitin matrix is filled with amorphous silica (SiO₂). The iron contained in the aqueous iron-oxide mineral is the metal that constitutes the largest proportion of the composition. Other metals such as sodium, potassium, calcium, and copper are present in different proportions depending on the sea snail’s exact geographic location.

Critical factors in durability

The most important reason that the sea snail’s teeth have such high durability is because the fibers of the aqueous iron-oxide minerals in the teeth are nano-scale. This is due to the fact that materials of this size are not affected by the conditions that reduce strength.

Another critical durability factor is the small length of critical fibers. Critical fiber length is a parameter that defines the length of a material required to transfer strain from the matrix to the fibers at the time of external pressure. To achieve maximum strain, the length must be greater than the critical length. Materials with a large critical fiber length can hardly reinforce the matrix because most of the strain is not transferred to the fibers and remains on the matrix. On the contrary, materials with smaller critical lengths can transfer the strain on the matrix to the fibers. Therefore, they serve as an effective reinforcement for the matrix.

Fibers of aqueous iron-oxide minerals are of a critical length of 420 to 800 nanometers. This is much smaller than the length of the fibers in the teeth of about 3.1 µm (micrometers). This shows that nanofibers are an effective reinforcer for the matrix and contribute greatly to the ability of the teeth to bear loads.

Besides the structure and composition of the snail’s teeth, its morphological shape is also important in providing strength. It ensures that the strain is evenly distributed all over the tooth.

Modeling of biomaterials

All these studies indicate the presence of high-strength composites, which is when a material obtained by combining two or more materials with different physical characteristics, in nature.

Sea snail teeth, which have been created as a highly resistant and strong biomaterial, act as an inspiration for engineering and material science. Their characteristics, such as content and design, are expected to be modeled in areas that require durability and rigidity.

These marvelous systems found in the natural world, sometimes in creatures as tiny as a snail or mollusk, serve as a reminder that nature is filled with wonders for us to explore.

References

· Barber, Asa H., Dun Lu ve Nicola M. Pugno, Extreme Strength Observed in Limpet Teeth,  Journal of The Royal Society Interface, April 2015, DOI: 10.1098/rsif.2014.1326, PubMed.

· World’s Strongest Natural Material Discovered, How It Works, Imagine Publishing, No. 71, p. 11.

· en.wikipedia.org/wiki/Limpet
www.iflscience.com/plants-and-animals/worlds-strongest-natural-material-limpet-teeth/

· www.newworldencyclopedia.org/entry/Limpet

· Barber Asa H., Lu Dun and Pugno Nicola M. “Extreme strength observed in limpet teeth.” 12. J.R. Soc. Interface. http://doi.org/10.1098/rsif.2014.1326

The parable of those who take to them other than God for guardians (to entrust their affairs to) is like a spider: it has made for itself a house, and surely the frailest of houses is the spider’s house. If only they knew this! (Qur’an, 29:41)

A prehistoric Greek fairytale says a young girl named Arachne was a superb spinner and knitted the most gorgeous cloth. She dared the goddess Athena to a competition. When Athena saw Arachne’s stunning work, she ripped the cloth and hit the young girl. Disgraced, Arachne committed suicide by hanging herself. Athena regretted and transformed Arachne into a spider, so that she could whirl repeatedly and endlessly. Arachnida is the scientific name for spiders. It comes from the young girl in the famous Greek fairytale.

Although usually feared and disliked by people, spiders in fact make life easy for us by feeding on mosquitoes, flies, and locusts, thus saving our crops and eliminate the need for man-made insecticides which pose environmental problems. Besides, spiders are much less dangerous than people think they are; most spiders are keen to avoid interaction with people and will bite only when wounded or scared. Even poisonous spiders are rarely as dangerous as popular myths would have us believe: though black widows are poisonous, and their bites painful, they rarely kill people. If handled properly and quickly the adverse consequences of a black widow’s bite typically diminish in a few hours, and, after a couple of days’ rest or cessation of activities, the victim will fully recuperate [1].

There are countless features of spiders. But their silk is exceptionally unique and this article covers its various aspects.

Spider silk

Biomaterials, having developed over millions of years, frequently surpass man-made substances in their properties. Spider silk is an exceptionally stringy biomaterial which is made almost completely of substantial proteins. Silk fibers have stretchy powers similar to steel and some silks are practically as elastic as rubber on a weight-to-weight basis. In uniting these two properties, silks disclose a hardiness that is two to three times that of artificial fibers like Nylon or Kevlar. In addition, spider silk is also antimicrobial, hypoallergenic, and completely biodegradable [2].

The power of spider silk, so fragile in manifestation, is astonishingly great. A filament can be outstretched as much as one half its normal length before breaking, and has a tensile strength exceeded only by fused quartz fibers. Fine fibers are sturdier than others, the power to some degree depending on the velocity with which they are pulled out of the spider’s body. The higher the speed, the superior the strength.

Most of the silken fibers are not single fibers but are made up of two or more strings. A thread may be as fine as a millionth of an inch in width but, frequently, it is ten or twenty times as dense, and the assemblage of these threads unsurprisingly creates larger threads of a diversity of thicknesses. Furthermore, some threads are gluey whereas others are not.

Scientific research demonstrates that a single thread of spider silk, thick as a pencil, could stop a 747 Jumbo Jet in flight, and that on an equivalent footing, the spider’s silk is stronger than steel, per unit weight. It has been shown that the dragline silk of the golden orb spider is one of the planet’s hardest threads.

Spiders employ silk for webs, but also for trap lines, draglines, ballooning lines, for egg pouches and nursery nets, for compartments in which to sleep through winter or to copulate, and for entrapping and wrapping their victims. Silk for all these objectives is not accomplished with one kind of gland; there are at least seven distinct kinds. A few distinctive spiders have as many as six kinds and probably have more than six hundred independent glands; others have fewer than this [1].

Mechanism behind the formation of spider silk

A batch of scientists headed by researchers from the RIKEN Center for Sustainable Resource Science (CSRS) have scrutinized spider silk and discovered that a formerly undiscovered organizational constituent is critical to how the proteins form into the beta-sheet conformation that gives the silk its extraordinary power [3]. If humans can cultivate equivalents to spider silk, they could be applied in industrial and medical applications. It is well-known that the beta-sheets in spider silk are significant to its strength, but how the sheets are created is scantily comprehended, making it difficult to produce synthetic variations. It is hard to comprehend the process: the silk is originally produced as soluble proteins, which very swiftly crystalize into a solid form.

To explain this, the CSRS scientists obtained silk proteins using genetically altered bacteria that can generate silk from a golden orb-web spider (Nephila clavipes) and then executed multifaceted examinations of the soluble proteins. They discovered that the reiterating area is comprised of two designs – unsystematic spirals and a design called polyproline type II helix. Their investigations confirmed that the polyproline type II helix is critical for the creation of the stiff construction, which can then be rapidly converted into beta-sheets, letting the silk be swiftly intertwined. Fascinatingly, it was discovered that pH – which is supposed to be significant for the molecular exchanges of the N- and C- terminus areas – does not play a significant role of the foldup of the recurring areas, and that it is rather the elimination of water and mechanistic forces through the silk gland.

According to Keiji Numata, who is a project leader of JST ImPACT and led the research group, “Spider silk is a wonderful material, as it is extremely tough but does not contain harmful substances and is readily biodegradable, so it does not exert any harmful load on the environment” [4]. Numata hopes that this discovery may lead to the production of artificial silk that will prove useful for society.

Analysis of silk

The silk itself is a material identified as a “scleroprotein.” When created in the glands it is a fluid; only when dragged outside the body does it solidify into thread. Once it was believed that contact with air produced the toughening, but it currently looks that the drawing-out activity alone is accountable for the change.

To carry out the exertion done by the glands, a spider is armed with spinnerets, usually six in number. These are as accommodating as fingers; they can be prolonged, compacted, and overall be applied like human hands. In the “spinning field,” where the spinnerets are congregated, single threads are joined into numerous compound threads, and some of the dehydrated threads may be covered with a gluey substance. Thus, a completed thread may be thin or thick, dry or sticky. It may also have the look of a bead-trimmed necklace. For the last kind, the spider spins rather unhurriedly and, drawing out the gluey thread, lets it go with a jolt. The liquid thus is organized in beads spread out lengthwise across the completed line.

The strand known as the dragline may be understood as a spider’s “life line” because it performs as a lifeguard in all kinds of situations. The dragline goes along with the spider, no matter where or how far it journeys, winding out from spinnerets at the back of the body. It forms a portion of the building of webs, it grips its tiny builder firmly in problematic places, and it helps in absconding from adversaries. When a spider is inactive in a web, the dragline enables a rapid descent and escape. It allows energetic chasing spiders to jump from buildings, cliffs, or any tall position with absolute security. [1]  

Benefits of spider silk to us

The silk of the silkworm could be very profitable and marketable. There are, however, challenges. One is the changing thickness of a spider’s strand; the other is that it doesn’t well endure the interweaving process. Housing and feeding large numbers of silkworms is not difficult. But housing and feeding large numbers of spiders? There are enormous difficulties.

Native inhabitants of New Guinea have used spider silk in a variety of conditions. They make fishing nets, traps, and such objects as bags, headdresses that will keep away rain, and caps. These are not formed from single threads but from tangled, warped threads. The aboriginals of North Queensland, Australia, look to spiders for their angling supplies.

Spider silk has been valuable to the manufacturers of such complex instruments as astronomical telescopes, guns, and engineers’ levels. The threads, being exceedingly fine but nonetheless robust, are outstanding for sighting marks. Throughout the Second World War, there was a significant demand for spider thread for surveying and laboratory instruments. Black widow spiders were utilized for the manufacture of this silk.

One drawback to the use of spider silk in industry is that it might slump in a moist environment. To overcome this problem, strands of platinum or etching on glass plates take its place in such instruments as periscopes and bombsights. [1]

Spider’s silk also might have healing properties. Due to its antibacterial properties and because the silk is abundant in vitamin K, it may be efficient at clotting blood. Because of the problems in obtaining and handling extensive amounts of spider silk, the largest known piece of cloth made of spider silk is an 11 by 4-foot (3.4 by 1.2 m) fabric made in Madagascar in 2009. Eighty-two persons labored for a period of four years to gather over one million golden orb spiders and extract silk from them. [5]  

Applications of spider silk

As mentioned, human beings have been using spider silk for thousands of years.

The manufacture of contemporary synthetic super-fibers such as Kevlar (bulletproof material) includes petrochemicals, which adds to pollution. Kevlar is also strained from concentrated sulphuric acid. In comparison, the manufacture of spider silk is totally ecologically sustainable. It is created by spiders at ambient temperature and pressure and is strained from water. Furthermore, silk is totally biodegradable. If the manufacture of spider silk ever becomes industrially practical, it could be a substitute for Kevlar and be used to create a varied extent of articles such as: bulletproof vests, wear-resistant lightweight clothing, ropes, nets, seat belts, parachutes, rust-free boards on motor vehicles or boats, biodegradable bottles, bandages, surgical thread, artificial tendons or ligaments, and backings for weak blood vessels. [6]

Synthetic spider silk [5]

Duplicating the multifaceted settings needed to make threads that are similar to spider silk has been difficult to both research and manufacture. Through genetic engineering, Escherichia coli bacteria, yeasts, plants, silkworms, and animals have been utilized to produce spider silk proteins. Yet, these synthetic threads have diverse, simpler features than those of a spider. Manmade spider silks have lesser and unsophisticated proteins than natural dragline silk, and have subsequently half the diameter, strength, and flexibility.

One tactic is to remove the spider silk gene and utilize additional life forms to generate the spider silk. Canadian biotechnology company Nexia effectively produced spider silk protein in transgenic goats that passed the gene for it; the milk made by the goats comprised noteworthy amounts of the protein: 1-2 grams of silk proteins per liter of milk. To make spider silk, Nexia utilized damp whirling and pressed the silk protein across minor extrusion cavities in order to mimic the performance of the spinneret, but this process was not adequate to duplicate the sturdier characteristics of innate spider silk.

In March 2010, investigators from the Korea Advanced Institute of Science and Technology was able to produce spider silk by means of the bacteria E. coli, altered with definite genes of the spider Nephila clavipes. This tactic removes the necessity of milking spiders.

It should be noted that the manufacture of spider silk is not easy and there are intrinsic difficulties. First of all, spiders cannot be cultivated like silkworms since they are flesh-eaters and will merely eat each other if in proximity to each other. The silk produced is very slight, so 400 spiders would be required to make only one square yard of cloth. The other problem is, silk also toughens when subjected to air, which makes working with it problematic.

A different tactic is to study how spiders whirl silk and then replicate this process to make artificial spider silk. The silk itself would also have to be synthetically produced. Chemical production of spider silk is not feasible at present due to the absence of information about the makeup of silk. Randolph V. Lewis, Professor of Molecular Biology at the University of Wyoming in Laramie, has introduced silk genes into Escherichia coli bacteria so that the recurring sections of spidroin 1 and spidroin 2 efficaciously come to form. Others theorize about the likely gene introduction into fungi and soya plants. It may also be possible to modify the silk genes for precise intentions.

Why a spider’s house is the frailest of houses

Spider silk is stronger than steel, but the Qur’an (29:41) states that the flimsiest of houses is the spider’s house. The per unit weight of the dragline silk of the golden orb spider is one of the world’s hardest fibers. Webs are combinations of many kinds of spider silk, all able to be produced by the same spider. The web radials are strong, but the somewhat feebler circumferential (quasi-circular concentric) fibers are flexible and gluey to absorb the energy of a flying insect and hold it in place. The strongest of all is the fiber, which the spider uses for transport, the dragline silk. In summary, the spider fabricates both sturdy as well as feeble fibers and the web it weaves to catch flying insects is weaker; this may be the reason why it is referred to in the Qur’an as the “frailest” of houses.

Conclusions

Scientists are foreseeing many potential uses for biosilk. Textile usages are noticeable one. The flexibility and potency of prevailing merchandises such as spandex and nylon have to be improved. Since it is lightweight, hardy and flexible, biosilk may also have uses in satellites and aircraft. More prominently, the new group of progressive things that spider silk investigation may cause has the prospective to alter our lives in innumerable manners that we can barely imagine. More than 72 years have passed since the inventions of Wallace and Carothers that gave the world nylon that led us into the age of polymers. Artificial spider silk may help produce super-performing clothes of the future. Earthquake resistant suspension bridges hung from cables of synthetic spider silk fibers may someday be a reality. [1]

References

1. Syed, I. B. : Spider Silks http://www.irfi.org/articles/articles_1_50/spider_silks.htm
2. Romer, L and Scheibel, T.: The elaborate Structure of spider silk, PRION, Oct-Dec. 2(4) 154-161, 2008. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2658765/
3. RIKEN Center for Sustainable Resource Science (CSRS). Scientists discover key mechanism behind the formation of spider silk. Materials Science. May 29, 2018, https://phys.org/news/2018-05-scientists-key-mechanism-formation-spider.html

4. Nur Alia Oktaviani, Akimasa Matsugami, Ali D. Malay, Fumiaki Hayashi, David L. Kaplan, Keiji Numata, “Conformation and dynamics of soluble repetitive domain elucidates the initial β-sheet formation of spider silk”, Nature Communications, 10.1038/s41467-018-04570-5 https://en.wikipedia.org/wiki/Riken
5. Service, Robert F. (18 October 2017). “Spinning spider silk into startup gold”. Science Magazine, American Association for the Advancement of Science. Retrieved 26 November 2017. https://en.wikipedia.org/wiki/Spider_silk
6. Vivienne Li, University of Bristol, Spider Silk and Venom. Molecule of the Month – July 2002. http://www.chm.bris.ac.uk/motm/spider/page4.htm

Where am I?

There are 46 chromosomes in your body, carrying 20-25 thousand genes. Chromosomes and the genes they contain shape the genetic memory of a human being. Genes can contain hundreds of features, and these are revealed over time. For instance, you do not have any teeth when you are a newborn, but the time when you will get your teeth is encoded into your genetic memory. Once genes receive the action command, teeth start to emerge.

There are hundreds of genes located on chromosomes, all the way from the chromosome number 1 and 2, to chromosome number 46. For example, there are around three thousand genes found on chromosome number 1. The Y chromosome, in charge of male development, only contains 125 genes. A distinct address (locus) for each gene on the chromosomes is recorded. If you ask about the address of the fibrillin gene that synthesizes me, it is 15q 21.1, i.e., 15th Avenue, Long arm street, 21st pl, Number 1.

In other words my residing address is the 1st subband of the 1st band of the 2nd region located at the long arm of chromosome number 15. We are three siblings, known as fibrillin1, fibrillin2 and fibrillin3.

We stretch and relax like an arch. We can expand and tighten like an inflated balloon and then return to our previous state. If by an error, we happen to fail to restore ourselves after inflation, the tissue’s architecture gets deformed and expanded fibers cannot regain their original shape anymore. When observed in veins, this situation is called an aneurysm. The frequency of this disease is approximately one in ten thousand, which is also called ballooning. That said, my flexing is necessary. Veins flex so that the blood pumping through them doesn’t cause any turbulence, as it would otherwise be during a vacuum occurring inside metal water pipes. Flexible sportsmen who do acrobatic moves do not compare with me. I can bend, curve, flex, relax and constrict, inflate, deflate and transform like elastic, from one shape to another, for your health and overall convenience – all because of the wondrous features granted to my nature.

What kind of a fiber am I?

I provide structural support for the fabrication of elastic fibers in the connective tissue as a protein synthesized according to the code of the fibrillin gene. In case of my failure or absence, weaknesses occur, especially in the connective tissues of organs that are rich in elastic fibers, such as the aorta, lungs, and eye balls. The iris (the colored part of the eye), pupil, and eye lens display changes in accordance with levels of light or distance of objects observed. These changes are controlled perfectly according to my work, and humans often don’t even notice this. We also help the eye lens constrict and relax. It can be understood that we are such a great blessing granted for your service. Of course, if we tried to count all the blessings we’ve been given, and never even consider, it would be impossible!

My weight is 350 kilo daltons. A Dalton is an atomic mass unit approximately equal to one hydrogen atoms’ mass, which is 1.66×10-24. I consist of 2.871 amino acids. I am formed by the sequential arrangement of 20 amino acids that exist in your body as the smallest unit of proteins. We bind each other to become 10-12 nanometers wide microfibers as the result of a process called polymerization that brings loops of a protein chain together. These microfibers are brought together with the elastin protein that provides elasticity in our body. The system that we form with elastic fibrils constantly serves the body’s blood vessels, primarily the vessels located in your eyes, heart, and many of your tissues, such as your skin and nerves.

What do I do? We fulfill commands that are requested from us in many tissues and organs, without any flaws. Scientists call us the wonderful building blocks of the body’s architecture. We can extend twice as much of our length. We are always on task: while you are breathing, when your heart is pumping blood and your stomach is digesting food, or the moment you are gazing at nature with your eyes. We are given the duty to prevent many organs from tearing, including the heart, lungs, stomach, and blood vessels. One of the places I work most frequently is the aorta, the body’s major artery. Your heart beats approximately a hundred thousand times a day. A high level of pressure develops in the arteries during the pumping process. You would suffer greatly without the help of our elastic fibers. Blood vessels would rupture, ending your life. This high pressure is tolerated only through the expansion of the vessel’s diameter without any decrease in length of the artery. This diameter regulation is designed so wondrously that blood flow remains the same; no shaking or waves are observed. This diameter control happens via the fibrillin protein located inside the vessel.

I also play a role in the vitality and tension of your skin. Skin is essentially a dense fibrous connective tissue composed of a protein called collagen. I am also one of the main elements of this connective tissue. As you age, this layer starts to dry and has lesser fibrous proteins; therefore, as fibers decrease, so does my tension, and I start to wrinkle. Elderly people do not like getting wrinkly, but this is your fate. Whatever you do, I will also age and die.

I cannot go without pressing this important issue: Staying under the sun for a long time degrades me. If done properly, sun light is useful for skin. But solar radiation damages the live tissues and organs. This radiation is an effective factor both in degradation of protein structures, and the formation of varicose veins and skin damage. It is reported in various sources that exposure to sun rays leads to alterations in the genetic material of skin. Ultraviolet rays speed up the degradation of skin. In medical language, this is called oxidation via free radicals. Please do not burn us and yourself while sunbathing. Even if you do not care for yourselves, you should still be considerate of us. If you say that sunbathing both helps, with vitamin D synthesis and reducing the risk of osteoporosis, I would like to remind you that for the vitamin D synthesis of skin, it is sufficient to expose your hands, feet and face to the sun.

How is life without me?

Though we were wisely designed, sometimes, you are tested by certain diseases in which we are not present. Absence, as they say, makes the heart grow fonder!

Life without me is unbearable. I could give a couple of examples, should you like. If I was not created, your skin would not be flexible. You wouldn’t be able to control your eye lenses. Your aorta would not be flexible and your heart, which beats thousands of times a day, would be torn under the high pressure in a short amount of time. Major problems would occur with the development of your stomach, lungs, and other organs.

I also have a significant job keeping TGF-Beta (which helps cells grow) function under control. To give you an idea of how important this is, imagine your communication system turned upside down. Now imagine how complicated are the communication systems connecting billions of people around the world, how a mess it would be when they are out of service. These are nothing when compared to the human body. There are 100 trillion cells in the human body, communicating with each other instantaneously. A cellular community that is fifteen thousand times more crowded than the earth’s population communicates via small molecules, like us. Cellular proliferation and tissue differentiation would fail if cells failed to communicate. The full spoon of food in your hand would not end in your mouth but maybe in your ear or your eyes.

If a mutation happens with the Fibrillin-1 gene, Marfan syndrome can occur. This disease, which was defined in the 1800s, is named after its discoverer. The frequency of this disease is one in five thousand. One of the major lethal consequences of Marfan syndrome is an aorta tear. This is in addition to many problems with the eyes, skeleton, and cardio-vascular systems. Many of the patients die in their 30s or 40s because of the flaws in the cardio-vascular system. Of course, death may occur at any age because of an aorta rupture. 14% of the patients with Marfan syndrome display chronic obstructive pulmonary disease (COPD), which is associated with breathing problems, because the integrity of lung tissue is compromised. Another disease I help prevent is called Ektopia lentis, in which the eye lens is displaced from its original position. Normally, I help eye functioning. When my fibers relax or constrict, depending on light, I help the eye to relax, enabling both near and far sightedness. With Ektopia lentis, anomalies on the front vestibule of the eye, a high degree of myopia, and retina damage occur.

If overproduced, I can cause another problem with the eye, called exfoliation syndrome. This is when fibrous connective tissue, like me, accumulates in the eye – it’s commonly called glaucoma, or ocular hypertension. In some people, as they age, a fibrous material like hair dandruff collects on the eye lens. This material, dislocated by movements of the iris, blocks the drainage channels that discharge the intraocular fluid. Eye pressure increases as the result of failed drainage. As you see, I am not a problem when I am synthesized normally, but can be trouble if over produced! My final request from you!

You have seen our amazing works and complicated functions. Therefore, please remember me and my friends. Please do not ignore our efforts and activities. Be grateful for the blessings provided through us, even if you can’t see them. And take care of us, please – don’t get carried away with too much tanning!

Dear Peter! I, your muscular system, would like to talk to you today; I allow you to walk and do all kinds of movements very easily. In the most recent essay of this department, the skeletal system, which works together with me, discussed how it protected your body and enabled you to stand straight and firm. Sure, this is true. However, as you know, huge rocks and trees can stand straight, too; but they do not have what you do-the ability to move. They are rigid and inflexible because they do not have a system that allows them to move.

You on the other hand, as the most splendid creation in the entire universe, have mobility. All animals have mobility at different levels, thanks to the muscular tissues, which work dynamically behind all the moving organs. However, you, human beings are like neither the animals nor the plants. You have not been created to live like a tree that is pegged down in earth or like an animal that unconsciously tries to meet only its biological needs. Our Designer, God, has made you and your descendants the most important of all creation. He has given you qualities that help you to discover the world, learn, invent and establish new civilizations. To realize such potential and to carry out such duties, you need to first have the freedom to make changes in your small immediate world, which can only be done through motion. In order to enable you with this ability to move, my Creator has put me at your service. I am a system that comprises hundreds of muscles and millions of packed cells.

My most important feature is the cells that move by burning sugar, like a motor consuming fuel in order to work. My cells can shorten and lengthen thanks to the intracellular fibrils (myofilaments) that contract and expand. As a result of each contraction, I pull the bone or the organ that I am attached to and cause it to move or change shape. With the exception of your heart, your bones and organs cannot move on their own. Their ability to move depends on the nature of the muscle they are attached to.

Indeed, I can be called both an organ and a form of tissue. I can use my contraction ability not only as muscle tissue, but also as an organ and a system which runs throughout your body. That is the reason why I appear in so many different types and shapes of muscle bundles. Let me give you an example to help you better understand what a muscle consists of: Let us imagine that a thin thread is like a basic muscular cell. Let us now bring together a great number of threads and make string out of them. Then, let us bring together those strings and make a clothes line. Next, let us bring together a great number of clothes lines and make a very thick rope. Now, imagine this thick rope as a muscle and an organ. Yet, this example is too basic compared to the sophisticated muscle.

Very thin cotton fibrils make up the thin threads. In the muscle fiber, like those cotton fibrils, there are two filaments formed by the two types of protein molecules called actin and myosin, which help in the contraction function. Those little filaments are placed facing one another and they slide past each other during the contraction, which causes the muscle fibers to shorten. That is how the contraction and relaxation of a muscle occurs.

Peter, do you think that coincidence plays a role in this complex and wonderful mechanism and the incredible structure which I have attempted to simplify with an example? Not even a simple thread can be produced without a thread-maker or a machine. Each of your muscles comprises billions of fibers, wrapped all around your bones and giving shape to your body. Can such a complex and delicately intricate structure exist on its own and be positioned in the best place it could possibly be?

My muscles consist of bundles that are made of thousands of muscle fibrils; the size and shape of each muscle depends on which bone it is attached to and what function it does. For example, the muscles that move the bones in your arms and legs are long and spindle-shaped; whereas the ones that are attached to your body can be circular, or triangular, or spread over a broad area. Whatever shape they have, the red skeletal muscles, which are attached to your bones, are very strong and they are voluntary muscles, which mean you can control their movement. When you walk, run, do something with your hands, lie down or stand up, you always use my red striated muscles. The strias (stripes) can only be seen under a microscope because of the histological structure of these skeletal muscles that make up a great part of your body.

My smooth muscles are involuntary muscles that work without your control. Their movements are slow and their contractions last longer, which is the reason why they do not tire easily. The smooth muscles lie in the walls of digestive system, blood vessels, and urinary tract, but I will not talk much about them since each system has referred to the smooth muscles within itself and in detail in previous talks. Because they are not attached to your skeleton to work, the smooth muscles do not play a role in your movements, such as walking around; they only work for the movements of your inner organs.

The third type of muscle belongs to your heart (cardiac muscle) and although the heart has a little striated muscle tissue, it, too works involuntarily. Therefore, you should be aware of the fact that it is the striated muscles which work for the movement of the skeleton and do the major job, and that it is this that we refer to when we say “muscle.”

A great number of bones have been created in order to support your body, and joints have been placed between those bones for them to take the proper shape according to every movement. However, none of those joints have the ability to move by itself. A door or a window, no matter how good it is, cannot be opened or closed without an outside force to pull or push it. In the same way, a joint needs a force to move it and that force is produced by your muscular system. There are around 340 muscles included in your muscular system. It has been estimated that all the muscles in your body perform 510 different functions! While some of those functions are bone movements in your joints, other muscles can perform movements without moving a bone at all. Muscles that are placed in your forehead, face, eye lids and abdomen are those kinds of muscles. They can help you look worried by wrinkling your forehead or grimacing when you are disgusted by something.

Keeping with tradition, the muscles that are included in my system have been named based on the function they perform. For example, the muscle which moves an organ part towards another part is called an abductor, while the muscle that straightens a joint is an extensor, and the muscle that bends a joint is a flexor; the muscle that raises a part of the skeleton is a levator, that which the muscle makes a part of an organ prone is a pronator, the muscle that rotates a part of an organ is a rotator and that which brings an organ into a supine position is called a supinator.

In order for you to make all the movements that your body needs, my muscle components have to be both very strong and flexible. The most important feature of my muscle components is that they can be trained and strengthened with a systematic workout. The main goal of all sportsmen who compete is to increase the strength and the endurance of their muscles. As a result of intense exercises with weight and speed, the number, the diameter and the length of my muscle fibers will increase. Thus, I can gain more power to be able to do more work and also gain the ability to contract faster.

However, in addition to all this training and exercise, genetic factors also play a role in my health. For this reason, not everybody who works out can become a good sportsman; but if the person has innate muscular and skeletal capacity, with good exercise this capacity can certainly be enhanced and developed. However, if a person does not have the proper muscular structure for a particular sport, it would be unfair to expect them to be a champion! Although my muscles always seem to be of the same type at first sight, I might show different behavior depending on the distribution of the special fibers inside them. Some of my fibers twitch fast and tire easily, some of them twitch slowly and tire later. Depending on the distribution of these different fibers, the movements and sport that every person can do differ from person to person. In this case, an athlete who can run only 100m and an athlete who can run 10,000m do not have the same development of muscles; they have different amounts and distributions of special muscle fibers.

The contraction of any of my muscles can occur in two different ways: If the pressure put on my muscle is stronger than the resistance of the tissue, the tension remains constant and the muscle shortens. This is called an isotonic contraction. If the pressure put on my muscle is equal to the resistance, the tension of my muscle increases and its length does not change. That is called an isometric contraction. The amount of force that occurs during the contraction of my muscle depends on its length and the amount of the stimulus.

In order to produce muscle contraction, an electrical signal is sent through a motor neuron to the synaptic gap, which is positioned between the muscle cell membrane and the nerve cell. As a result, a chemical reaction occurs, which, in a very short time, causes the actin and myosin proteins in the muscle fibril to slide past each other and thus shorten the fibril, contracting the muscular cells. During this reaction, the temperature also rises a little and the total heat generated by all the muscles determines your body temperature. For this reason, in cold weather, my muscles vibrate, increasing your body temperature and trying to maintain it. You may now understand why moving the parts of the body in cold weather helps people avoid from getting sick or freezing. As you can see, every act of my Creator is quite purposeful. He can create two or even more functions within one task: Through your muscles, He not only provides you with the ability to move freely, but heat is also produced and you are protected from getting cold.

When a muscle fiber contracts frequently as a result of successive electrical impulses from a nerve fiber, it becomes tired after a while and needs rest. In this case, other muscle fibers which have not contracted for a while will take over and continue the job. However, if the electrical impulses from the nerve come too frequently and my muscle fibers do not have an opportunity to rest, a condition of constant contraction, which is known as physiologic tetanus, occurs.

The tension receptors that are placed on my muscles help maintain the harmony and coordination of all your movements including walking and running, bouncing and sitting down. They do this by constantly signaling the nerve system and providing feedback about the condition of my muscles, and about the speed and the intensity of contraction. Thus, through these receptors which control and coordinate my muscle activities, the well-being of my system is ensured. It is this that prevents you from wobbling when you walk, or helps you to take a spoonful of soup to your mouth without spilling it.

Like any other tissue or system, I, too, have some special disorders. The most common disorders are: weakness, malformation, muscles that develop and move involuntarily and habitually, especially in your face (tic), infected muscles (myosite), muscle dystrophy, muscle rigidity (the Stiffman Syndrome), benign or malignant muscle tumors (leiomyom, rhabdomyoma, or Rhabdomyosarcoma). These disorders differ in their degree of severity and risk.

Dear Peter! You have now seen that each muscle helps your organs to move, holding your bones and giving shape and function to your body, making you a beautiful model and an inspiration for sculptors. You may have understood that this is a work of knowledge and might; there is no way that the myofibril in my one cell could form by itself as a result of a coincidence.

Irfan Yilmaz is a professor of biology at Dokuz Eylul University, Izmir, Turkey.

I consist of 217 bones in your body (however, since the bones in the thigh and sacrum areas fuse together in order to form a stronger bone, their number decreases, and the anatomists accept the number of bones as 206). I have 22 skull bones, 33 spinal bones, 24 rib bones, 64 bones in the hands, the forearms, the arms and the shoulder girdle and 66 bones in the feet, the legs, the thighs and the hip area. In addition, I have 6 small ear bones, 1 breastbone and 1 hyoid bone (at the root of your tongue), which make up the total of my 217 bones. It is quite amazing that so many different bones have cooperated with each other and contributed to such a perfect system.

Each piece of my skeleton has been created with special shape and quality that is proper to its place and duty. The bones that protect your brain are flat, whereas the bones in your arms and legs are long and cylindrical; while the bones in your wrists and ankles are short and rounded, your hips and girdles have been made of wide and big bones. The craggy surface of my bones makes it easy for the muscles to attach to them firmly. Each bone has certain durability that protects me from undue weight, flexure, twisting, and pressure. Bioengineers carefully examine my bones that have been created in a perfect form for where they are positioned and for what they do. They take my wonderful structure as a model, and they use it for producing new technology such as buildings or bridges. As you know, constructional engineers have to be very careful in their estimates of material and durability. They have to use different materials for different places, and these points will be exposed to forces like pressure, compression, tensile, or flexure (bending). If the estimates of the materials are not made accurately, the building or the bridge can easily collapse. When you humans build a strong building, it might be too heavy and bulky, resulting in a waste of material and money. Even if you use good quality material, if you do not use it in the right place, all your work might be unusable. Unlike human beings, the Creator has made me such a delicate and well-balanced system, in which you cannot find any material missing or unnecessary or any wrong line in a particular bone. That can only be explained with the boundless knowledge of God the Almighty. He knows exactly how you will be able to do hundreds of different movements in all your life-including running, lying down, jumping, lifting a heavy item, playing sports, writing, and eating. In order to allow you to perform those actions, He has created a perfect design for each piece of my bones and the joints that connect them.

In building my structure, He has used materials in different hardness and durability to make your movements easy. The first material is the bones. Not all bones are the same. Compact bone (dense bone) is found in my hardest parts. For example, the long bodies of the femur, the tibia, and the fibula (bones between knee and ankle) are made of compact bone, and they are very rigid and strong. Softer bones, which look like a sponge, are found at the edges of those long bones and within my flat bones. The second material, my cartilage, is placed at the bone edges and on the joints where, by absorbing excessive pressure, the cartilages are able to prevent damage to the surface of joints and to the nerves that go through the vertebra. My cartilages achieve this thanks to their soft and flexible substance, which also provides a perfect aesthetical quality. In addition, because of this flexibility given by God, cartilages protect the bones from breaking easily (depending on the rigidity of the bones), and they balance your strong and abrupt movements. If it were not for the cartilages on the joints, not only the bony surface would be damaged but also my movements would be mechanical and harsh just like those of a robot. My third material is the ligament, and its main substance, the fibers, that are made of collagen protein. The fibers of this ligament are very strong straps, which hold my bones and cartilages together.

All my joints and tendons that fasten the muscles to my bones are tied up and strengthened by those ligament fibers, which vary in shape, length, and quality. The collagen fibers are also used as the basic substance of my bones and cartilages. Those fibers, which are placed among the cells of the tissues of my bones and cartilages, provide the tissues with strength and durability. The distribution of the fibers in my bones is determined according to the direction and intensity of the pressure coming upon me. To see an example, you can look at the head of my femur (between my knee and thigh) where it makes a joint with the thigh bone. The spread and design of the fibers placed right at this joint requires a flawless calculation, which you can better understand by examining a diagram of it.

Not all my joints are flexible in the same degree. For example, the joints in your skull, which protects your brain and sensorium, resemble the toothed blade of a saw. They are strong joints, which are firmly locked with each other, and they allow no mobility. Of course, it can be no one but God who is able to give my skull such strength and hardness, since He knows exactly how much protection my delicate brain, eyes, and ears need. Moreover, my skull is not shaped simply as a bony capsule; at certain places, God has put little channels for the blood vessels to go through, little cavities for the sensory organs, and a big hole for the spinal cord to connect to the brain. Can any of these be formed by coincidence? The joints between the vertebrae (little bones of your spine) are more movable than the skull and less movable than your fingers. They help to allow you stand upright and sit, twist, and bend or lie down. The joints in my shoulders and legs are freely movable, which enables you to do movements in all directions. Perhaps the most wonderful of all are the joints in your hands! It would not be a distortion to say that-behind all your work to make a discovery or an invention or a new technology-is the skillful creation of my hand joints. Everything that you use with your hands-including all kinds of tools, furniture or appliances, art works, and books-can be produced or utilized only through the perfect ability of my joints to move. If my fingers lacked that great ability to move freely, many of my thoughts or intentions would not be able to be translated into actions.

Your muscles that help in the movement of all my movable parts have to attach to my bones to be supported. While one end of your muscle holds my bone firmly, the other end pulls another bone with the help of the joints. That is how movement in your body occurs and how you can take a step, do exercise, or wave your hand.

Although not as much as the skin, I have a very good ability to renew myself. When one of my bones is broken, if you line up the two pieces exactly in relationship to each other, the bone cells, called osteoblast, quickly divide to produce new cells, fill the gap, and repair the break. Then, I take calcium salts, which harden and strengthen the area, and gain back my health. Calcium is a vital mineral in the growth of bones. When you are a little but growing fetus in your mother’s womb, you need plenty of calcium for your bones to develop. If your mother gets sufficient amounts of dairy products, fish, and green vegetables, there will not be a calcium deficiency. But the good news is that, even if an expectant mother does not get enough calcium, the unborn baby is unlikely to have calcium deficiency. That is because Our Lord God, whose Mercy is infinite, provides baby with calcium by making it be absorbed from the mother’s bones and teeth and ensures the healthy development of the baby’s tiny skeleton. The mother has the willpower to feed herself, but since the baby is helpless, its need is met by the calcium taken from the mother’s body. After birth, the baby has to be nourished well with calcium and vitamin D by means of healthy foods, and it has to have enough exposure to sunlight. In order to maintain my health, my biggest need is calcium salts and vitamin D, a vitamin that needs the body’s exposure to the sun in order to contribute to healthy bone growth. For this reason, you have to take care of me especially at your young age. If you do not get those salts and vitamins, your bones will not develop well, and this could result in skeleton disorders.

The cavities within my bones are called marrow cavities (or medullar space) and they have important duties too. If your bones were filled merely with bony substance, my weight would be too much, and you would not even be able to stand up. Moreover, my bones would not be as strong as they are now. According to calculations with static forces, a rounded iron stick, which is filled, is less durable than the one with a hole in it, and the stick with a hole in it can be bent easily. My long, rounded bones have been designed according to that principle, and they are more resistant to twisting and bending. Another important function of my marrow cavities is to house the production of little red blood corpuscles, which have important duties within the blood. When you are young, all my bone marrows are red, and they produce red blood cells. Then, slowly after the puberty, the bone marrows in my long rounded bones start to turn yellow, get fatty, and produce white blood cells. The spongy bone marrows in my flat bones, however, stay red in color during your entire life, and they keep producing red blood cells.

The shape and size of my bones and their proportions to each other all determine the shape and quality of your body. Although I develop according to my genetically inherited qualities, the loads that you made me carry and outside impacts all affect my development significantly. When you are a baby, my bones start out as cartilages. At young ages when I am just starting to become bony, if I have to carry too heavy things, I start to harden and become bony too fast. This leads to the incomplete growth of the length of your neck bones, and your arms and legs which will remain too short. Playing basketball or volleyball stimulates the growth and elongation of your bones. Mineral salts, vitamin D, and the hormones secreted by the parathyroid gland play role in the ossification of my bones. The elongation of my long bones is achieved by the cell division and formation of new cells in the areas called epiphysis, which are the rounded ends of the long bones. This bone-lengthening process ends after puberty. While the lengthening of bones stops earlier in girls around ages eighteen or nineteen, it continues in boys until the ages twenty-one or twenty-two, which is the reason why men are generally taller than women.

When you were born, all of my components were cartilages, which are very soft and flexible. That is the measure that the all-knowing and all-caring God has taken, to ensure that neither you nor your dear mother gets any harm during your birth. If I became bony before the birth, your mother could die, and many of your bones could break during the birth. However, thanks to the cartilaginous components, which are like plastic, the risk of death and becoming disabled decreases greatly. As you become older, the cartilages are replaced with bone cells, and the accumulation of calcium salts make me hard and bony. The cartilages remained only on the joint surfaces and at the ends of ribs.

Dear Peter! Now it is time to ask a question that might bother you a little: have you ever been at a reopening of a grave? Sometimes in graveyards, when they do not have extra space for new burial, the dead person’s body is buried next to a body that belonged to a family member. When the grave is reopened, you can clearly see that, except for the newly buried body, all parts of the other dead body have been mingled with the earth. You can see that only my skull and other bone components have remained without decaying. After a very long time, those bones will decay too but much later than my other tissues. In the past, when the Holy Qur’an was just being revealed, some people refused to believe in God and the Day of Judgment, and asked: “Who is going to resurrect those decayed bones?”(Qur’an 36:78). The following verse is an answer: “Say, ‘He who created them in the first place will give them life again: He has full knowledge of every act of creation’” (Qur’an 36:79). In many other verses of the Qur’an, which deal with both the first creation and the Judgment Day, also mention decayed or dried bones, which still exist after many years. This means that God wants to draw your attention to the bones of your body! Perhaps, He is saying: “O, Peter! I created your bones, your joints, and your whole skeleton flawlessly. I took all measures for you to be able to live your life perfectly; to the littlest details, I created a delicate body, mind, and soul free of defects or faults. When I created you that perfectly, do you think I took something else as a model, or applied someone else’s plans? Not at all! Therefore, I, who created you out of nothing with my infinite knowledge and might, will of course be able to recreate you!”

Well, Peter! That is how I understand my Creator and the message of His Holy Book, which appeals to all of humanity. Your ability of comprehension and appreciation is more perfect than mine. Therefore, each time you move your body or body parts, just think of the wonderful pieces of bone accompanying and supporting your organs. Reflecting on them for some time will gain you a fresh view of life. That is what I wish as your skeleton!

Irfan Yilmaz is a professor of biology at Dokuz Eylul University, Izmir, Turkey.

Each creation is a work of art. All animals and plants, as well as every human being, are unique and priceless. And those who appreciate their value are like antique dealers as in the passage above. I recently had the chance to listen to such an “antique dealer,” Joanna Aizenberg of Bell Laboratories/Lucent Technologies, and witnessing the appreciation of the valuables she presented to us helped me better understand Said Nursi. Both the valuable object she was talking about and her appreciation of it were equally inspiring for me, and this is the reason why I have decided to share this story with you. Without any further ado, here is the story of a sponge species called the Venus’ Flower Basket and its “eternally” incarcerated residents: a pair of shrimp. Now, you must find what is hiding behind all this; after all, it is the eyes that look but the heart that perceives.

Venus’ Flower Baskets (Figure 1a) are vase-like sponges that grow upright on the sea floor of the Pacific Ocean, mostly around Japan. They have a very sophisticated mesh structure which caused medieval Europeans to assume they were glasswork made in China. In Japan they are called Kairou-Douketsu (together for eternity) and given as wedding gifts, since they generally house a pair of mated shrimp which are trapped in their cavity. As you have probably already understood, our story is about the engineering secrets of these sponges and their relationship with their guests.

The design

The skeleton of the Venus’ Flower Basket is made of silica, which is a very brittle material (remember the glass windows that you broke with your football when you were a kid; they were made with silica). How can these amazing creatures withstand the pressure and the currents present at the sea floor or the disturbance caused by two shrimp? The secret lies in the hierarchical construction of their cylindrical cage-like structure. As can be seen in Figure 1b, their skeleton is made up of beams that run perpendicular and parallel to the axis of the sponge, which forms a rectangular grid. This grid is further supported by beams that run diagonally in both directions. Finally, this whole structure is reinforced by ridges that spiral around. But these are just the macroscopic hierarchical levels of the construction. Now let’s start from the very first level of this hierarchy and try to understand how each level adds to the stability of the sponge.

The basic building block of the Venus’ Flower Baskets is a fiber composed of silica nano-spheres (Figures 1i and 2a) that grows around an organic filament (the black dots at the center of the circles in Figure 1f). Though this fiber is not very stress tolerant, due to the size of the spheres from which it is made, in the next level of hierarchy it is toughened by alternating organic and silica sheets that form a concentric lamellar (fine, alternating layers of different materials) fiber structure. The thickness of each layer in the fiber decreases from 1.5 (: 1/1000 mm) at the center to 0.2 towards the periphery (Figures 1f, 1g and 2b). Hence any crack that is initiated at the periphery is halted at the organic interlayers and while the thinner outer layers lessen the depth of crack propagation, the thicker inner layers enhance mechanical rigidity (in addition to their mechanical stability, these silica fibers are endowed with optical properties which are superior to man-made fibers, which will be discussed later on in the article).

Figure 1. Structural analysis of the mineralized skeletal system of Euplectella sp. (a) Photograph of the entire skeleton, showing cylindrical glass cage. Scale bar, 1 cm. (b) Fragment of the cage structure showing the square-grid lattice of vertical and horizontal struts with diagonal elements arranged in a chessboard manner. Orthogonal ridges on the cylinder surface are indicated by arrows. Scale bar, 5 mm. (c) Scanning electron micrograph (SEM) showing that each strut (enclosed by a bracket) is composed of bundled multiple spicules (the arrow indicates the long axis of the skeletal lattice). Scale bar, 100 mm. (d) SEM of a fractured and partially HF-etched (25) single beam revealing its ceramic fiber-composite structure. Scale bar, 20 mm. (e) SEM of the HF-etched (25) junction area showing that the lattice is cemented with laminated silica layers. Scale bar, 25 mm. (f) Contrast-enhanced SEM image of a cross section through one of the spicular struts, revealing that they are composed of a wide range of different-sized spicules surrounded by a laminated silica matrix. Scale bar, 10 mm. (g) SEM of a cross section through a typical spicule in a strut, showing its characteristic laminated architecture. Scale bar, 5 mm. (h) SEM of a fractured spicule, revealing an organic interlayer. Scale bar, 1 mm. (i) Bleaching of biosilica surface revealing its consolidated nanoparticulate nature (25). Scale bar, 500 nm. Figure and captions from ref. 2.

Fibers of different diameters reinforced this way are then bundled loosely in a silica matrix (Figure 1d and 1f). The different diameter of the fibers in the bundle and the weak lateral bonding between them are essential for increasing the strength of the bundle against crack propagation. At the next level of hierarchy, these bundles are used as building blocks of the cylindrical cage of the sponge, being arranged horizontally and vertically into a square grid. This grid in turn is reinforced by diagonal bundles that run in both directions along every second square lattice. The minimum number of pin-jointed struts (i.e. ones that are free to rotate at the joints) per node needed in order to form a rigid two-dimensional grid has been shown to be six; this is the number present in the skeleton of the Venus’ Flower Basket. In fact, if the diagonal bundles were to run along every square lattice, the number of struts per node would be 8, which would be redundant for the stability in the skeleton.

At the early stages of the growth of the Venus’ Flower Basket the struts are not connected at the nodes. However as the sponge gets older the struts are joined by a silica cement which itself also has a lamellar structure (Figure 1e). Hence, while the younger sponges are flexible, the older ones are stiff; this also has important implications for the symbiotic relation that the sponge has with its guests, the shrimp. (This issue will be discussed in detail when the lifecycle of the shrimp is examined.) While the resulting grid is stable in two dimensions, in three dimensions it may still suffer from exterior effects, such as ovalization. This problem however is solved at the next level of hierarchy by the helical ridges that surround the grid (Figure 1b). The absence of the ridges at the base of the skeleton of the sponge where the cage diameter is small, and their increased density further up the cage where the diameter is much greater is proposed as evidence supporting this argument. Finally, this whole cage structure must be anchored to the sea floor in a way that will withstand the bending stresses caused by the currents. This is managed through the use of the fibers that have been discussed earlier; they are used as connectors between the base of the sponge that is anchored to the sea floor and the vertical struts of the skeleton, resulting in a flexible connection that enables the cage to swing freely in the currents (Figure 1a).

As a conclusion, it can be said that “The resultant structure might be regarded as a textbook sample in mechanical engineering, because the seven hierarchical levels in the sponge skeleton represent major fundamental construction strategies, such as laminated structures, fiber-reinforced composites, bundled beams, and diagonally reinforced square-grid cells to name a few.”

Now let’s concentrate more on the fibers (or spicules) that anchor the cage to the sea floor. These anchorage spicules (a term used for describing the skeletal structures of sponges which comes from the Latin word speculum, meaning the head of a spear or arrow)* are 5-15 cm in length and 40-70 um in diameter. In the above discussion we have briefly discussed the cross-sectional structure of these fibers that gives them their flexible, but resistant nature. Here we will focus on the optical properties of these spicules. But before doing so, let’s briefly explain how optical fibers work.

Optical fibers are silica fibers of a 5 to 80 um diameter that are coated with a cladding layer; light waves can travel in these for long distances by constantly bouncing off the cladding. The reason for this is the refractive index difference between the silica core and the cladding layer. Refractive index (n) is a measure of the ability of a medium to change the phase velocity of light and cause the light waves to bend while leaving one medium and entering another (refraction); in the case of fiber optics, leaving the core and entering the cladding. However, if the refractive index of the second medium is lower than that of the initial one, the incident light waves that have an incidence angle higher than a critical value or critical angle can be reflected back to the first medium and this is what happens in fiber optics (See red ray in figure 2). If the core diameter is small (5-10 um), light rays can propagate only through a single path in the fiber (which runs parallel to the fiber axis), hence these type of fibers are called single-mode fibers (See Figure 2a). If the core diameter is larger however, (60-80 um) several paths are accessible, and more paths will have incidence angles that are greater than the critical angle, hence they are called multi-mode (See Figure 2b).

Now with this information in mind, let’s have a look at the characteristics of the anchoring spicules of the Venus’ Flower Basket. First of all, as mentioned in the previous discussion, the lamellar structure of these spicules prevents crack propagation, which is the main failure mode of commercial silica fibers. This lamellar structure, however, also determines the dependence of the optical behavior of the spicules on the environment in which they are embedded. For instance if the spicules are embedded in an epoxide medium with a refractive index of 1.57, the spicule as a whole would not be able to act as an optical fiber, due to the smaller refractive index of the cladding. However, since the core region of the spicules has a slightly higher refractive index than that of the cladding, the core acts as a single mode fiber in such an environment (see Figure 2a). In sea water-the spicules’ native environment-which has a refractive index of 1.33, the whole spicule acts as a multimode fiber, since the refractive index difference between the core and the cladding is much smaller than that between the cladding and the surrounding sea water.

Another advantage of these spicules over man-made fibers is their formation/production parameters, which are ambient temperature and pressure; these enable the introduction of impurities into the silica. Though at first it may not sound as if impurities are a positive characteristic, these impurities are very important for increasing the refractive index of silica and act as dopants (impurity elements added to a semiconductor lattices in low concentrations in order to alter the optical/electrical properties of the semiconductor). The core section of the spicules, for instance, shows increased sodium concentration, which is the cause of the higher refractive index of this section. Such dopant introduction in the silica during the fabrication process, however, is not possible in the case of man-made fibers, due to the very high processing temperatures.

In addition to this, the spicules have crown-like caps at their base and thorn-like structures throughout their middle section. While the crown-like termini most probably are used to anchor the sponge to the ocean floor, it has also been shown that the waveguiding efficiency of the spicules increases when the illumination comes through the end that has the crown-like structure. Hence, it has been proposed that this structure may be acting as a light harvesting lens. The thorn-like structures, on the other hand, share the lamellar construction of the spicule body, and the light guided through the body branches out to these spines and emerges at the tip. Since sea water comes into contact with the tip at an almost perpendicular angle to the guided light, the coupling is pretty efficient. Hence the combination of crown-like ends and thorn-like structures forms optical networks that collect and distribute light. However, at the depths inhabited by the Venus’ Flower Baskets there is no accessible light source. If one accepts the fact that there is no waste in nature-whether one believes in “creation” or “evolution”-the existence of such an advanced network-like structure as a part of a sponge-the most primitive animal-is at least thought-provoking. In the case of sponges that dwell in shallower waters with similar spicules, it has been postulated that such spicules gather and provide sunlight for the sponge’s endosymbiotic algae. However, at the depths at which the Venus’ Flower Baskets live, direct sunlight is not available. However it has been suggested that if light sources, such as bioluminescent microorganisms (bioluminescence is the production and emission of light by a living organism as the result of a chemical reaction during which chemical energy is converted to light energy) or chemiluminescence (emission of light as the result of a chemical reaction) exist, their light may be efficiently distributed by the sponge and act as an attractant for juvenile shrimp that are searching for a host. But for now these suggestions are just speculation and merit further investigation.

Before concluding this section, we should also note that, as a natural outcome of their construction/composition, these spicules do not have as great a transparency as their industrial counterparts and light cannot be transferred over long distances with them. However, it seems this is not a problem for the Venus’ Flower Basket as, apparently, they just need fibers of 5-15 cm to survive and it is the scientists who need to figure out a way to incorporate the traits of the Venus’ Flower Basket into industrial fibers.

The love

As mentioned in the introduction, the Venus Flower Basket hosts a pair of mated shrimp. These belong to the family of Spongicolidae, the Spongicala japonica. These shrimp, which can be as “big” as 9 mm in length, spend most of their lives in their host sponge. Though studies about them are limited, it is believed that before permanently being entrapped in their host, the shrimp have two free- living periods. The first one is just after hatching when they are small enough to exit through the mesh of the sponge. During this period they exit and re-enter their cages and live in a group with their parents and other juveniles. Studies suggest that the females generally stay with their parents until sexual maturity, whereas the males tend to leave their original host and live a solitary life until they reach a length of about 4 mm.

The second free-living period comes at the time of sexual maturity, when it is believed that the male and female mate outside and then invade a host, or the female searches for a host that is already occupied by a solitary male. During this stage, the shrimp have a body length of 3.5 to 6.5 mm which is bigger than the mesh size of the host sponges. Though this seems puzzling, it is thought that the mated shrimp enter the sponge in its flexible stage-when it may be easier to penetrate through the mesh-and get trapped there “forever” as the sponge grows older and stiffer. In fact this theory is supported by the finding that several flexible sponge specimens host solitary and young mated shrimp, whereas in the stiff specimens only very few solitary and young mated shrimp have been observed.

References

1. “Biological glass fibers: Correlation between optical and structural properties.” J. Aizenberg, V. C. Sundar, A. D. Yablon, J. C. Weaver, and G. Chen, Proc. Nat. Ac. Sci. 101 3358 (2004).

2. “Skeleton of Euplectella sp.: Structural hierarchy from the nanoscale to the macroscale.” J. Aizenberg, J. C. Weaver, M. S. Thanawala, V. C. Sundar, D. E. Morse, P. Fratzl, Science, 309 275 (2005).

3. “Fibre-optical features of a glass sponge – Some superior technological secrets have come to light from a deep-sea organism.” V. C. Sundar, A. D. Yablon, J. L. Grazul, M. Ilan, J. Aizenberg, Nature 424 899 (2003).

4. “Skeletal growth of the deep-sea hexactinellid sponge Euplectella oweni, and host election by the symbiotic shrimp Spongicola japonica” (Crustacea: Decapoda: Spongicolidae). T. Saito, I. Uchida and M. Takeda J. Zool., Lond. 258 521 (2002)

5. “Pair formation in Spongicola japonica (Crustacea: Stenopodidea: Spongicolidae), a shrimp associated with deep-sea hexactinellid sponges.” T. Saito, I. Uchida and M. Takeda J. Mar. Biol. Ass. U.K. 81 789 (2001).

Note

*. Also defined as, one of the minute calcareous or siliceous bodies that support the tissue of various invertebrates (Merriam-Webster’s English dictionary)

Our Creator has solved every potential problem which living things might experience by creating one optimal solution among every alternative.These perfect solutions open new horizons for men, and they also act as guides in the development of science and technology. The book titled “Engineering in Nature” details many striking examples.1

In recent research, it has been discovered how the thread of a spider can contribute to fiber-optic technology. A crucial challenge in photonic technology is to produce the tiny optic fiber that is used as a conductor for a light beam in nano-scaled optic circuits. Yushan Yan, of the University of California in Riverside, has taken an important step forward in this technology by covering the thread from a spider web with a glass-like material and then removing the thread after the material has hardened. By utilizing this technique, it is possible to produce threads that are 1/50000th the diameter of human hair and that have a radius of 2 nanometers (1 nanometer being one billionth of a meter).

Not only will this discovery be applicable in photonic technology, it will also increase the resolution in optical microscopes, or, alternatively, these threads could be turned into nanoscale test tubes in a new breed of sensors that can suck up single molecules of a particular chemical.

A research group at the University of California cut a thread 1 centimeter long from the web of the giant spider of Madagascar, the Nepila Madagascariensis, and pasted the two ends of the thread to a card. Then they repeatedly dipped this thread into tetraethyl orthoslicate solution. After this, the thread that had undergone this process was dried and heated to a temperature of 420 Celsius. The string decreased by one fifth of its original radius and the process resulted in the production of tiny tubes with a radius of one micrometer.

There are plans to make use of the web of the Stegodyphus Pasifiu-a spider which uses a thread of a radius of 10 nanometers and which is found in the Middle East and Southern Asia. This will enable scientists to use thinner fibers. After heating, a thread with a radius of 2 nanometers is attained. Until this latest finding, it was only possible to produce fibers with an interior radius of 25 nanometers.

Fiber optic researchers do not hide their enthusiasm for this new simple and cheap technology. It is expected that it will be used in the field of supra-molecular chemistry; that is the study of very miniature environments. In these environments the reaction-speeds increase and completely different reactions occur. For such experiments carbon nano-tubes are being used at the present time. The tubes made from fibers obtained from spider webs will enable scientists to create more sensitive environments. It is also thought that it will be possible to create microscopes with a higher resolution by using tinier fiber optic catheters.

Such microscopes would be used to observe events that are shorter in duration than the wavelength of light, yet at the same time, these microscopes would not cause the sample to be harmed. Electron microscopes harm the sample since the features of the technology used necessitate this. Currently, these microscopes use a scope that has been made from very thin glass tubes. These fibers are relatively thick, measuring about 100 nanometers in radius. Yet, by means of this new technology, these new microscopes can be developed and biologists will have brand new opportunities to study events that have not been visible before. Surely, it is not possible to say that the immaculate biological structure and incredibly small thread employed by the spider can be explained by simply putting its creation down to chance or by stating that it is a product of nature.

These perfect examples that can be observed in nature will lead to fundamental changes in our understanding of the universe; they will enable great leaps in terms of making our life more comfortable and, most importantly, they will be helpful in realizing how the Divine Power and Art can be present together and be in harmony.

References 

• M. Sami Polatoz, Tabiatta Muhendislik [Engineering in Nature], Kaynak, Istanbul: 2003.
• Danny Penman, Spiders Weave a Web of Light, New Scientist,
• 22 March 2003, p. 20.