Material in Squid Beak and Abrasion Resistance - Literature review Example

Material in Squid Beak and Abrasion Resistance Material in Squid Beak and Abrasion Resistance Introduction The squid is an organism classified in the kingdom Animalia, the phylum Mollusca, the class Cephalopoda, the subclass Coleoidea, the superorder Decapodiformes, and the order Teuthida. The order, in which squids are found in Teuthida, has an estimated 300 species. The squid has a head that is distinctive, arms, a mantle, and a bilateral symmetry. The number of its arms is eight along with two tentacles that are elongated. Biologists note that the current form of the squid has evolved over time from other different and unique forms to gain certain important features such as an advanced group of organs used in the sensory function. The tentacles are an intricate part of the result of evolution along with its beak. As biological organisms, squids have fully developed organ systems like the reproductive, digestive, nervous, and the cardiovascular system. The major part of this review constitutes the beak of the squid, which has continue to amaze researchers with its hardness. In addition, its attachment to a soft body. Squids have a head that is the base for both the tentacles and the arms. The beak, which is the main subject of this review is located on the mouth. As noted by ****, the beak is horny and sharp. It is said to be made up of cross-linked proteins and chitin. What is its purpose? It has been opined that it is utilised for tearing prey into consumable portions and killing it at the same time. What is unique about the beak is its toughness. Nevertheless, in spite of the beak being hard, it is said to lack any minerals. Such is the robustness of the squid’s beak that it has been found in the stomach of whales intact. Because of the lack of minerals to harden the beak, the question has always been how the beak is so hard yet in normal biological settings, it is the minerals that result into the hardness of a tissue. However, the feeding of the squid necessitates that the beak is hard and tough to cut and tear flesh. On examination, the beak of a squid has been compared to that of a parrot. It is composed of two parts that are sharp. Surprisingly, it is implanted into the head, which is composed of soft tissue. Normally, it is usually darker than the other body parts. However, the darkness reduces as the beak moves towards the base, which is the soft tissues of the head. Why is the beak hard? It has been discovered that, the darkness of the squid’s beak results from a direct relationship with the amount of proteins forming it. Researchers say that a chitin meshwork in water forms the lighter parts of the beak that are near the base. However, the dark part of the beak is comprised of amino acid that have been translated and are hydrophobic. These amino acids are asserted to be 3, 4-dihydroxyphenylalanine or DOPA as commonly abbreviated (Meyers & Chen, 2014). Researchers state that when the whole Squid beak is dried up, it has a Young modulus of between five and ten GPa. Nevertheless, if it has some water-content, the same dark part of the beak is estimated to have a decreased Young modulus of around 5 GPa (Meyers & Chen, 2014). When it goes to the extreme, then the Young modulus decreases further. What is the Young modulus? The Young’s modulus is the measure of the stiffness or rigidity of a substance, which is measured when tension is in action (Davis, 1994). Hence, with this know-how of what the Young modulus is, it is evident that the Squid beak goes through certain variations in the range of stiffness due to the presence of water in chitin (Meyers & Chen, 2014). Further, various authors of the Squid beak continue to talk of the features of the non-mineralisation aspect of this beak. It is indicated that there is the utilisation of organic molecules to tightly bind the protein network that constitute the beak. The use of this organic molecules regulates the Young modulus of the organic materials that are not mineralised. Though various Squid types do exist, the best example that has been used by researchers is that of the Humbolt or Humboldt squid. As noted by Poinerm (2014), the scientific name for the Humbolt squid is Dosidicus gigas. The author notes that it has a very strong beak. The strong beak as indicated by the author is utilised in the fracturing, killing, and disjointing the hard exoskeletons of other marine organisms. As opined, the beak is harder than the teeth of a human being by a very large number. The continuous change of the beak from its harder tip to its soft body is a unique aspect of the beak. What causes this? The author says that the continuous change results from a gradual variation in the quantity of the cross-linked proteins that form the structure of the beak. Under very minute measurements, say nanometres, it has been observed that the proteins forming the beak’s structure develop a distinct combination, which leads to the gradual change from soft to the hard stiff tip of the beak. In addition, Dufresne, et al. (2013) indicates that the squid beak is composed of a chitin and protein mixture. The authors state that the beak is made up of layers of chitin, which are organised in such a manner that they are perpendicular to the outermost surface of the beak. The chitin layers are also placed in a way that they face the direction of the tip of the beak. Due to the variation in the materials in the beak, there is a colouring difference from the tip to the base of the squid beak. The tip is said to be highly tanned while the base is not tanned at all. Why is this so? It is so because of black tints that arise from the oxidation of molecules that have catechol (Ruiz-Molina, et al., 2014). The authors also seek to note the presence of DOPA proteins in the squid beak along with chitin. In a research undertaken by the authors, they specificall take note of the direct association between the degree of colouration and the hardness of the beak. The region of the beak that is near its base has a small Young modulus, while that at the extreme end of the beak, whih forms its beak has a high Young modulus. An interesting aspect of the beak is the opposite association of the stifness with the chitin that is part of the material constituting it. It is known that chitin is a very stiff subsatance. However, studies have shown a different aspect of the chitin in the squid beak. What is this different aspect? The different aspect is that the regions of the beak that have the highest concentration of chitin have a very small stiffness. That is, they are not hard. Why is this so? It is so because of the mass ratio of the water and chitin. The water and chitin ratio is conspicuously high in these regions unlike in the part of the beak that is very stiff. It is said to be 0.5 times greater at the base than at the tip of the beak. Hence, the counter relationship between the scattering of DOPA-rich proteins and water throughout the beak of the squid show that the extent to which chitin is soluble is influenced by the existence of compounds that are obtained from catechol. One major material in the beak of squids is chitin. According to Dufresne, et al. (2013), Henri, a French scientist isolated chitin in 1811. As a polymer, it is second to cellulose in terms of quantity and is nostly used to form the exoskeleton of organisms. As stipulated by the authors, it has a key function in the graded regulation of the processes utilised in the bio-mineralisation of molluscs, of which the squid is a part of. As a polymer, it has been discovered to comprise of beta 1, 4-associated N-acetylglucosamine. The other characteristics are that it is of low reactivity, and has a lot of crystals. The reason for its low reactivity is due to the hydrogen bonds that exist among its composition. As a result of the hydrogen bonds, chitin is an inelastic material, swells easily, and is of reduced solubility. Glycosidic bonds join together the rudimentary units of chitin. How do they do this? Dufresne, et al. (2013), indicates that the first carbon of N-acetylglucosamine links the fourthc carbon of the next acetylglucosamine. As determined by research, the chitin organisation within a structure, for example, the squid beak, are arranged in a parallel way with discrete layers. For each succeeding chitin layer, there is a variation of between three to five degrees. Hence, the order of chitin in terms of hierarchy ensues from a molecular entity to a succession of molecules, to the microfibril to the fibril collection to the bundle that is said to be fibrous in nature, and finally to the Bouligand structure (Dufresne, et al., 2013). The association of chitin with proteins is intricate. Studies note that chitin has never been found to exist on its own. Hence, there must be the presence of proteins along with chitin. To illustrate this, some researchers, as evidenced by Dufresne, et al. (2013), have come up with models to describe the associatio between chitin and proteins. In one model described by the author, they note that there exist a protein covering made up of sub-units that are organised in helix like manner. Thus, for every chitin core, the model indicates that there are six sub-units of the respective protein. In some other cases, direct binding of proteins to chitin does not occur. Hence, it could be that the proteins constitute a matrix that hold up the protein-chitin composite. Nevertheless, the chitin and protein correlation is not well defined and more research needs to be conducted to determine if a precise relationship does exists (Dufresne, et al., 2013). Read More