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

Africa has many fresh water sources such as Lake Tanganyika, Lake Victoria, the Zambezi, Nile, and Juba Rivers. Theoretically, Africans should be able to at least, adequately sustain healthy life with this amount of water (Whiteford & Whiteford, 2005). On the other hand, several issues affect the water sources making them either inaccessible, or dangerous to use. Diseases form and spread all through Africa, deteriorating life due to deficient amounts of clean water (Whiteford & Whiteford, 2005).

The reason for the water problems majorly involves dams and deforestation, along with pollution. Firstly, dams provide irrigation and hydropower, but hidden underneath these benefits are the massive and long-term detriments of destroying the well-known system of flood-plain agriculture and deforestation due to incomplete dam projects. Flood-plain agriculture is the classic system of agriculture that was mainly used along the Nile River as well as several other rivers in Africa. These traditional systems of agriculture depend on the annual floods in order to fertilize and water their crops. Water, as well as the silt that once functioned as fertilizer, are now built up behind the dams and are unusable. Secondly, deforestation dries up the land even more because interception and transpiration from trees stop, causing more forest fires and destruction of habitats. Deforested land becomes a dried up desert absolutely unusable by all habitats, especially humans (Jobin, 1999). Thirdly, pollution caused by poor sanitation techniques, in addition to industrial and chemical pollution are major reasons for the decline of life in Africa. Poor sanitation techniques lead to human and animal feces infest water, leading to increase in diseases related to water. The industrialization and urbanization in some parts of Africa leads to high levels of modern environmental health hazards. This results in other severe health problems indirectly related to water. For example, in the Nairobi River Basin in Kenya, there were effluent concentrations of elements such as nickel, copper, and lead, which were 60, 600, and 120 times higher than recommended (Nweke and Sanders, 2009). Another major cause of chemical pollution all across Africa is the use of pesticides in agriculture which have been detected in streams and rivers in different regions. These pesticides contaminate soil, water, air, and food sources, posing serious health threats to Africa’s populations. Endosulfans, as well as more dangerous organochlorines, such as DDE and DDT have recurrently been detected at water sources near agricultural areas in South Africa. This contamination has been confirmed to regularly exceed the “European drinking water standard of 0.1 g/L” (Nweke & Sanders, 2009). This contamination not only poisons potential sources of food, but it also destroys habitats which all have a chain reaction pertaining to the sustainability in Africa. In summary, these factors influence the water quantity and quality in Africa. It also negatively affects people’s habits regarding water usage. If people realize they have little water, they ration it ineffectively. For instance, they will take up water usage reducing habits such as not washing hands, clothes, food products, dishes, themselves, etc. leading to less hygiene and increasing the likelihood of getting disease. If there is plenty of water but it is contaminated, the pollutants in the water source will cause diseases. Therefore, due to poor water management in Africa, diseases related to water have been severely affected.

Water-related diseases differ from waterborne diseases in that the disease is not directly caused by the water consumed. Instead, the vector of the disease uses water as a breeding ground from which the vector then emerges. Common water-related diseases include malaria, yellow fever, schistosomiasis or bilharzia, and onchocerciasis or river blindness (Whiteford & Whiteford, 2005).

Schistosomiasis, also known as bilharzia, is a disease that is highly prevalent along the Nile River as well as all other fresh water resources throughout Africa caused by parasitic worms and snails (Jobin, 1999). The most common parasitic worms that cause bilharzia in humans are Schistosoma mansoni, D. haematobium, and S. japonicium (Centers for Disease Control and Prevention, 2010). Infection occurs when the larval stage of schistosomes search for a human host while swimming in the water. After parasitizing the human circulatory system by penetrating the skin of an individual in contaminated water, they reproduce in the human gut or bladder by laying their eggs there (Centers for Disease Control and Prevention, 2010; Jobin, 1999). These eggs pass out of the body by means of human waste and reach aquatic habitats of snails (Jobin, 1999). After the eggs hatch, they develop into larvae which penetrate the snail, developing further and “multiplying by astronomical factors” (Jobin, 1999, p. 66). The parasite larvae then leave the snail continuing the reproduction cycle. As written by Jobin (1999), “bilharzia is a debilitating disease which can cause early death of persons parasitized by large numbers of worms” (p. 68).

Symptoms of bilharzia include developing a rash or itchy skin within days of infection. Within 1-2 months of the infection, symptoms such as fever, chills, cough, and muscle aches may also appear, but people tend to have no symptoms at this early phase. The eggs that travel in the body can also cause inflammation and scarring. As reported by CDC (2010), infected children may “develop anemia, malnutrition, and learning difficulties.” All of these symptoms are reactions of the body to the eggs produced, and not by the worms themselves. Treating schistosomiasis is essentially effortless; you must take a pill 1-2 days (Centers for Disease Control and Prevention, 2010).

Since the health care systems in some African countries are shoddy, and the majority of these populations cannot afford treatment or drugs, prevention is the most efficient technique to fight disease throughout the continent (Falola & Heaton, 2007). Bilharzia can easily be prevented in Africa by avoiding swimming in fresh water sources, health education, drugs, focal application of biocides to kill snails, and improved water supply and sanitation are also required to stop the spread of the infection. Using feces and urine contaminated water is a major cause of spread of the disease due to the nature of the parasite’s reproductive system, but another equally important issue is intensifying agriculture. Increased agriculture results in runoff with high concentrations of nitrogen and phosphorous, which act as a fertilizer (Peace, 2006). These compounds trigger an increase in aquatic weeds, the ideal habitat for snails, which causes increased bilharzia transmission. In addition, since people wanted to clean the water sources from the weeds, they would manually try to clean the water supply, without taking any precautions. This exacerbated the situation by exposing themselves to the disease (Jobin, 1999).

An example of the relationship between agriculture along with irrigation, and bilharzia as well as malaria transmission can be seen in the Gezira-Managil Irrigation System in Sudan. In 1925, when the irrigation system was first constructed, the overall agricultural intensity increased by 300%, this was because the natural system had been altered with. Naturally, the water should have dried out by April-May, but instead it ran 100% of the time. The Gezira-Managil Irrigation system became the main source of income in Sudan, producing 3/4 of the gross national cotton production. By 1970, the proliferation of agricultural pests, aquatic weeds, snails, mosquitoes and silt in the canal lead to the decline of the agricultural system. As a result, cotton was infested by the white-fly, pathogenic viruses and bacteria multiplied in the water making it unusable. Malaria mosquito populations increased, attacking at night and increasing transmission of disease, since there were no longer dry seasons to destroy their habitat. Similarly, bilharzia snails increased since the unnatural, man-made system had constructed an exceptionally ideal habitat for them, attacking during the day as people waded in the waters, and intensified the transmission of the disease. People who worked on the fields and near the irrigation system got infected, not being able to work on the nearly non-existent cotton fields. The country’s gross income changed from approximately US $228 million to US $76 million by 1981. There was no longer any money, which meant no more facilities for community water supplies and sanitation, increasing disease and unemployment, resulting in even less money in a seemingly endless cycle (Jobin, 1999).

There are many factors that act as obstacles in the way of African well-being. The most prevalent type of disease in Africa is waterborne and water-related. Sheik-Mohamed & Velema (1999) report that “major causes of mortality and morbidity seem to be preventable infectious diseases.” Govender et al. (2011) similarly state that “diarrheal diseases are an important cause of morbidity and mortality in low- and middle-income countries” and that these diarrheal diseases can be prevented simply through improved water quality. Every 8 seconds a child dies from a disease related to having either unclean or not enough water. Diseases linked to water kill more 5 million people each year – ten times the amount of people killed in wars (Whiteford & Whiteford, 2005). These statistics are outrageous. Every human should have the right to have clean water. Every human should have the right to live in a healthy environment and be in good health.

References

• Centers for Disease Control and Prevention. (2010, November 2).
• Schistosomiasis: General Information. Retrieved October 2011, from Centers for Disease Control and Prevention: http://www.cdc.gov/parasites/schistosomiasis/gen_info/faqs.html
• Falola, T., & Heaton, M. M. (Eds.). (2007). HIV/AIDS, Illness, and African Well-Being. Rochester, NY: University of Rochester Press.
• Govender, T., Barnes, J. M., & Pieper, C. H. (2011). Contribution of water pollution from inadequate sanitation and housing quality to diarrheal disease in low-cost housing settlements of Cape Town, South Africa. American Journal of Public Health , 101 (7), e4-e9.
• Jobin, W. (1999). Dams and Disease. London, UK: E & FN Spon.
• Nweke, O. C., & Sanders, W. H. (2009). Modern environmental health hazards: a public health issue of increasing significance in Africa. Environmental Health Perspectives , 117 (6), 863-870.
• Sheik-Mohamed, A., & Velema, J. P. (1999). Where health care has no access: the nomadic population of sub-Saharan Africa. Tropical Medicine and International Health , 4 (10), 695-707.
• Whiteford, L., & Whiteford, S. (2005). Globalization, Water and Health. Santa Fe, New Mexico: School of American Reasearch Press.