Microstructure, mechanical, and biomimetic properties of fish scales from Pagrus major

Protective materials and structures found in natural organisms may inspire new armors with improved resistance to penetration, flexibility, light weight, and other interesting properties such as transparency and breathability. All these attributes can be found in teleost fish scales, which are the most common types of scales in modern fish species. In this work, we have studied the structure and mechanics of fish scales from striped bass (Morone saxatilis). This scale is about 200–300 µm thick and consists of a hard outer bony layer supported by a softer cross-ply of collagen fibrils. Perforation tests with a sharp needle indicated that a single fish scale provides a high resistance to penetration which is superior to polystyrene and polycarbonate, two engineering polymers that are typically used for light transparent packaging or protective equipment. Under puncture, the scale undergoes a sequence of two distinct failure events: First, the outer bony layer cracks following a well defined cross-like pattern which generates four “flaps” of bony material. The deflection of the flaps by the needle is resisted by the collagen layer, which in biaxial tension acts as a retaining membrane. Remarkably this second stage of the penetration process is highly stable, so that an additional 50% penetration force is required to eventually puncture the collagen layer. The combination of a hard layer that can fail in a controlled fashion with a soft and extensible backing layer is the key to the resistance to penetration of individual scales.

/pdf/structure-and-mechanical-performance-of-a-modern-fish-scale-12s8802ewf.pdf

Structure and Mechanical Performance of a “Modern” Fish Scale

Regeneration of teleost fish scale

Palaeohistology of the bones of pterosaurs (Reptilia: Archosauria): anatomy, ontogeny, and biomechanical implications

http://www.chemistry.uoc.gr/demadis/pdfs/43.Principles%20of%20demineralization.%20Part%201.pdf

Principles of demineralization: modern strategies for the isolation of organic frameworks. Part I. Common definitions and history.

In Sarcopterygii ( Latimeria, Neoceratodus, Protopterus, Leptdosiren ) and Amiidae (Amia) collagen fibrils of the basal plate are packed in bundles whereas they remain isolated in Teleostei. The basal plate looks like plywood, a system of superimposed layers of parallel fibers or fibrils the directions of which rotate with a regular angle in two successive layers. The double twisted plywood is constituted of two imbricate systems, the odd and the even, where the rotation of the fibrillar directions is right-handed in Sarcopterygii and lefthanded in Amiidae and numerous primitive Teleostei. The orthogonal plywood, with its two main orthogonal fibrillar directions, characterizes the evolved Teleostei and some more primitive ones. In most teleostean species, as in Amia and Protopterus , mineralization of the basal plate in elasmoid scales involves Mandl's corpuscles that mineralize without contact with a pre-existing calcified tissue; they grow and coalesce with the neighbouring ones and fuse to the mineralizing front. Their shape is directly influenced by the local arrangement of the collagenous fibrils. In two teleostean families (Osteoglossidae and Mormyridae) Mandl's corpuscles are completely lacking but spreading of mineralization in the basal plate has a peculiar aspect. Whatever that may be, the various characteristic organizations of the skeletal tissues or isopedine that constitute the basal plate of osteichthyan elasmoid scales, all are varieties of bone tissue that have undergone more or less important specialization linked to the general regression of dermal ossifications and to functional adaptations.

François J. Meunie

Papers

Spatial Organization and Mineralization of the Basal Plate of Elasmoid Scales in Osteichthyans