Samples

Name:

Tutor:

Subject:

Date:

Chiton Teeth

Introduction

Chitons are marine organisms in the family of molluscs that belong to the class of Polyplacophora; they are omnivorous and about 800 species exist; however, a few genus such as Lepidochitoma are actively carnivorous. It dwells in the littoral or shallow part of the ocean where it attaches itself on the rocks. Its body is oval shaped, but flattened from back to the front. It is covered with a shell, made of eight separate and overlapping plates held by a leathery girdle; this explains why it belongs to the class Polyplacophor, which means bearing many plates. Some genus can be found in deep waters where they hide under the rocks as a way of protecting themselves from the strong waves and predators. They have a mouth on their dorsal part with teeth used to crash food (Nordsieck 2).

Figure 1: Shape of the Chiton

Figure 2: Chiton’s dorsal part showing eight plates Figure 3: Labelled dorsal part

The Chiton Teeth

Nordsieck reports that chiton teeth are the hardest compared to any other teeth (5). They use their teeth to rasp rocks as they search for food inside the rock crevices and cracks. Their teeth are not only hard, but also not brittle. The reasons why they have such hard teeth has been studied by chemical analysts; chiton’s teeth are capped with magnetite making it harder than the calcium rock substrate rocks. They use the teeth to scrap algae off the rocks because algae are tightly attached to the substrate (Mann 20). The teeth have iron oxide backed with hydroxyapatite at their cutting edges. Chitons are believed to synthesize the ferromagnetic mineral constituting its tooth. The synthesis of the ferromagnetic mineral serve two functions, the obvious function is the formation of their strong teeth (Kirschvink and Lowenstam 193). The second function is in navigation because they are sensitive to the localized magnetic fields. Importantly, the chiton teeth exist in a radula that comprises of hundreds of rows of teeth; the rows are 3 cm average length (Jones and Rao 4). However, during the feeding process the rows of teeth slowly wear off contributing to the composition of oceanic magnetite and iron ( Kirschvink and Lowenstam 201). As they wear out, they are continuously replaced; this creates a continuous supply of magnetite to the sediments. Due to its magnetic nature, it contributes significantly to the magnetism existing in sediments.

Figure 4: Arrangement of the chiton teeth

The Structure of the Constituents of the Chiton tooth

It is noted that although magnetite and the iron oxide, which are the major components of the chiton tooth when combined cannot equal the hardness of the chiton tooth. Gordon and Joester explain that the living things have a natural ability to control the properties and structure of the minerals in their tissues (194). The organic matrix interacts with the mineral by controlling its polymorph and morphology, the level of control varies from case to case. The chiton tooth has three separate parts; each of its parts consists of different chemical compositions within the polysaccharide chitin framework (Jones and Rao 3). The radula work as a conveyor belt that synthesizes and supplies rows of teeth. The underlying cells provide the materials for mineralization. Kirschvink, and Lowenstam describes the process of the teeth formation as multi-staged; the first stage involves the formation of the first 5 to 12 pairs of teeth by the odontoblast cells at the back or posterior of radula, the first pairs are not mineralized hence, it is colorless (194). The second stage involves capping the next 3 to 5 pairs by a hydrous oxide material called ferrihydrite. The third stage is mineralization of the next 25 to 29 pairs of teeth, the color of the teeth changes from brown due ferrihydrite to black due to magnetite (Kirschvink and Lowenstam 194). The thickness of these pairs of teeth is relatively large due to the capping with magnetite. The last stage is the continuous thickening of the new pairs of teeth due to the capping process. It is accepted that the synthesis of magnetite by the chitin uses the ferrihydrite though a series of processes involving reduction, removal of oxygen, dehydration, and change from the hexagonal-hematite structure to a cubic inverse-spinel structure (Kirschvink and Lowenstam 195). The shape and size of the resultant magnetite grains determine the magnetic properties of the teeth.

Figure 5: shows the chiton tooth structure; parts c shows thickening due to capping process.

The Nanometer‐Scale Phenomena in the Chiton Teeth

As noted the size of the chiton teeth is small, likewise the grain size of its components is at a nanoscale. According to the quantum effects rule, the properties of the materials change as their size either increase or decrease; concisely, material properties depends on its size. Examples of properties that change due to the size of the material are fluorescence, melting point, magnetic permeability, electrical conductivity, and chemical conductivity (National Nanotechnology Initiative 3). Basing on the hardness of the chiton teeth and comparing it with the hardness of individual constituents, it can be deduced that the nanometer‐scale phenomena is applicable to the scenario. The magnetite, which is chemically called Iron (11) or Iron (111) Oxide has different properties at a nanoscale.

Example of a Structure Engineered To Mimic the Biological Property

The application of biomineralization in daily life is in the engineering of histidine, which is one of the components of histamine. Histidine has been incorporated into protein-polymer hybrids used in the mediation of temperature in metals and pH sensitive gels (Sigel, Sigel and Sigel 315). While synthesizing histidine, the relationship between hardness and zinc content was examined, it was found that by reducing the amount of zinc the hardness of the product reduced. The net effect of the situation was formation of a metal able to bind to a protein to increase hardness. The stability of the product was tested using mass spectrometry, although the technique does not provide the best method to measure stability.

Another application of the biological process is in the electronic sector; the sector strives to develop faster devices, more hardy, compact, and consuming less power at a lower cost. For this to be achieved; there was a need to reduce the cell size, this was a practical application of nanotechnology (Edelstein and Cammaratra 567). Although the cells were reduced in size to exhibit different properties, there was a need to increase the coordination between the different components of the electronic device. It required changing the memory design and introduced the compact memories that use the scanning tunneling microscopy technique (Edelstein and Cammaratra 567). The memory uses miniature cells an equivalent of one atom. The implementation of nanotechnology in electronics has enabled production of hardy materials yet smaller in size.

In conclusion, the chiton teeth and its hardness rendered a lot of research to discover how size affects the formation and the final properties of a material. However, even among the chitons, the strength of their teeth vary depending on the genus and the species under investigation. The variation explains why some were omnivorous while others were clearly herbivores (Brooker and Shaw 65). For example, in the C. apiculata species the magnetite capping covers the posterior and the anterior surface while in P. albida there is only a small covering of the anterior cusp. In the two cases, the hardness of the teeth is different (Brooker and Shaw 66). Importantly, Brooker and Shaw notes that the difference in the hardness is not only in the composition of the mineral, but also in the grain alignment (66). There are discoveries that other minerals such as magnesium and phosphorous exists in the teeth of some species. The reason behind this is speculated to be the surrounding composition of the ocean waters resulting to the integration of these minerals together with the magnetite. The synthesis of magnetite by the chitons has contributed significantly to its existence in the substrate. The nanotechnology phenomenon naturally employed by the biological organisms has increased man’s ability to make strong things.

Whereas the study of the chiton teeth structure and how it is made fast is amazing; more studies need to be done to determine existing variances. Understanding the variances may help humanity if engineering more products with the same composition but different properties. It is obvious now that nature facilitates and influence more discoveries in the engineering sector. As a source of inspiration, its conservation will help man achieve more in the engineering and other sectors.

Works Cited

Brooker, Lesley and Shaw, Jeremy. “The Chiton Radula: A Unique Model for Biomineralization Studies”. Advanced Topics in Biomineralization.2012. Web. Accessed on

Edelstein, E. S and Cammaratra, R.C. Nanomaterials: Synthesis, Properties and Applications ( 2nd Ed.). 2011. Web. Accessed on

Gordon, Lyle and Joester, Derk. “Nanoscale Chemical Tomography of Buried Organic- Inorganic interface in the Chiton Tooth.” Nature. Vol. 469 p. 194 – 197. 2011. Web. Accessed on

Jones, W. and Rao, N. R. Supramolecular Organization and Materials Design. 2008. Web. Accessed on

Kirschvink, L and Lowenstam, H. “Mineralization and Magnetization of the Chiton Teeth: Paleomagnetic, Sedimentologic and Biological Implications of the Organic Magnetite”. Earth and Planetary Science Letters Vol. 44, p 193 – 204. 1979. Web Accessed on

Mann, Stephen. Biomineralization: Principles and Concepts in Bioinorganic Material Chemistry. 2001. Web. Accessed on.

National Nanotechnology Initiative. What’s So Special About the Nanoscale?. Web. Accessed on

Nordsieck, Robert. The Living World of Molluscs. 2012. Web Accessed on

Sigel, Astrid, Sigel Helmut, and Sigel, Roland. Biomineralization: From Nature to Application.

Web. Accessed on