Elasmoid Scales Research Articles

Характеристики эласмоидной чешуи рыб и ее фракций, по данным ИК-Фурье-спектроскопии

Elasmoid scales of pike-perch (Sander lucioperca), white amur (Ctenopharyngodon idella), carp (Cyprinus carpio), freshwater bream (Abramis brama) and crucian carp (Carassius carassius) were processed without hydrolysis by “dry” method in order to study the characteristics of the obtained finished product, which determine its further use as additives for food and other purposes. The essence of the method consisted in washing the scales, its subsequent drying, grinding and separation, with obtaining two fractions enriched with both organic (cotton-like product) and inorganic (powder) components. FT-IR spectroscopy was used to characterize the scale samples and their enriched fractions. Characteristic bands known for collagen, in particular for Amide I, Amide II, Amide III, Amide A, were observed in the IR spectra of all the samples studied. The bands (inorganic part) at ~1022 cm–1 and at ~599 cm–1 indicate valence asymmetric vibrations of PO43– groups. Numerous bands for all experimental samples in the wavelength region 3900-3500 cm–1 can be caused by vibrations of OH groups, which is associated with the presence of water in the tested samples. Comparison of the absorption intensity in the region of characteristic frequencies of collagen and hydroxyapatite calculated by the IR method can be one of the approaches for the development of a rapid method for the determination of their quantitative content in fractions obtained from fish scales. Organic and mineral additives from fish scales can be recommended as components of formulations of various food products, as well as raw materials in tissue engineering, orthopedics and dentistry.

Elasmoid fish scales as a natural fibre composite: microscopic heterogeneities in structure, mineral distribution, and mechanical properties.

The elasmoid scales in teleost fish serve as exemplary models for natural fibre composites with integrated flexibility and protection. Yet, limited research has been focused on the potential structural, chemical, and mechanical heterogeneity within individual scales. This study presents systematic characterizations of the elasmoid scales from black drum fish (Pogonias cromis) at different zones within individual scales as a natural fibre composite, focusing on the microscopic structural heterogeneities and corresponding mechanical effects. The focus field at the centre of the scales exhibits a classical tri-layered collagen-based composite design, consisting of the mineralized outermost limiting layer, external elasmodine layer in the middle, and the unmineralized internal elasmodine layer. In comparison, the rostral field at the anterior end of the scales exhibits a two-layered design: the mineralized outermost limiting layer exhibits radii sections on the outer surface, and the inner elasmodine layer consists of collagen fibre-based sublayers with alternating mineralization levels. Chemical and nanoindentation analysis suggests a close correlation between the mineralization levels and the local nanomechanical properties. Comparative finite element modelling shows that the rostral-field scales achieve increased flexibility under both concave and convex bending. Moreover, the evolving geometries of isolated Mandle's corpuscles in the internal elasmodine layer, transitioning from irregular shapes to faceted octahedrons, suggest the mechanisms of mineral growth and space-filling to thicken the mineralized layers in scales during growth, which enhances the bonding strength between the adjacent collagen fibre layers. This work offers new insights into the structural variations in individual elasmoid scales, providing strategies for bioinspired fibre composite designs with local-adapted functional requirements.

Anatomy, development and regeneration of zebrafish elasmoid scales

Vertebrate skin appendages – particularly avian feathers and mammalian hairs, glands and teeth – are perennially useful systems for investigating fundamental mechanisms of development. The most common type of skin appendage in teleost fishes is the elasmoid scale, yet this structure has received much less attention than the skin appendages of tetrapods. Elasmoid scales are thin, overlapping plates of partially mineralized extracellular matrices, deposited in the skin in a hexagonal pattern by a specialized population of dermal cells in cooperation with the overlying epidermis. Recent years have seen rapid progress in our understanding of elasmoid scale development and regeneration, driven by the deployment of developmental genetics, live imaging and transcriptomics in larval and adult zebrafish. These findings are reviewed together with histological and ultrastructural approaches to understanding scale development and regeneration.

Cannibal predatory habits and their relationships with body shape and swimming pattern in the Cretaceous fish Dastilbe crandalli Jordan, 1910 from the Araripe Basin, Northeastern Brazil

Dastilbe crandalli is a small to medium-sized fossil Chanidae species, between 65 mm and 180 mm in length, without dentition, feeding mainly on algae and small planktonic and benthic organisms. The fusiform and hydrodynamic body shape combined with the forked fin and elasmoid scales allow them to develop high speeds and less drag in the water, proving to be useful for escaping predators and predating on fish, including small specimens of D. crandalli. The presence of fossils showing predation among specimens of D. crandalli from the Cretaceous of Araripe Basin evidences cannibalism behavior in this species.

Immunolocalization of Some Epidermal Proteins and Glycoproteins in the Growing Skin of the Australian Lungfish (Neoceratodus forsteri).

Here we report the immunolocalization of mucin, nestin, elastin and three glycoproteins involved in tissue mineralization in small and large juveniles of Neoceratodus forsteri. Both small and larger juvenile epidermis are mucogenic and contain a diffuse immunolabeling for nestin. Sparse PCNA-labeled cells, indicating proliferation, are found in basal and suprabasal epidermal layers. No scales are formed in small juveniles but are present in a 5 cm long juvenile and in larger juveniles. Elastin and a mineralizing matrix are localized underneath the basement membrane of the tail epidermis where lepidotriches are forming. The latter appears as "circular bodies" in cross sections and are made of elongated cells surrounding a central amorphous area containing collagen and elastin-like proteins that undergo calcification as evidenced using the von Kossa staining. However, the first calcification sites are the coniform teeth of the small juveniles of 2-3 cm in length. In the superficial dermis of juveniles (16-26 cm in length) where scales are formed, the spinulated outer bony layer (squamulin) of the elasmoid scales contains osteonectin, alkaline phosphatase, osteopontin, and calcium deposits that are instead absent in the underlying layer of elasmodin. In particular, these glycoproteins are localized along the scale margin in juveniles where scales grow, as indicated by the presence of PCNA-labeled cells (proliferating). These observations suggest a continuous deposition of new bone during the growth of the scales, possibly under the action of these mineralizing glycoproteins, like in the endoskeleton of terrestrial vertebrates.

Development and structure of the skin in the Australian lungfish (Neoceratodus forsteri) in relation to epidermal adaptation of tetrapods

AbstractAnalysis of skin development in the Australian lungfish, Neoceratodus forsteri, indicates that keratinocytes form 2 to 3 irregular layers in tadpoles of 2–5 cm in length and are fully stratified (7–12 layers) in juveniles of 16.5–26 cm in length. The epidermis produces mucus and mainly contains intermediate filament keratins of acidic nature but also a minute amount of neutral‐basic keratins (pI 7.0–7.3), which is unique among fish. The latter keratins of 60–62 kDa, are generally present in tetrapods but the specific gene structure and amino sequence of acidic, neutral and basic keratins in N. forsteri are presently unknown. No other epidermal proteins are detected although biochemical data suggest the presence of non‐keratin proteins, including a basic type (pI 8.0–8.2) of around 32 kDa of molecular weight. The spinulated bony layer of elasmoid scales contains glycoproteins involved in mineralization, such as osteonectin and osteopontin. Also, alkaline phosphatase, involved in calcium precipitation onto the collagen matrix, has been detected in scales of juveniles up to 26 cm in length. The present review concludes that the knowledge of the data derived from epidermal and dermal protein annotation from the recently sequenced genome of this fish species will contribute to address the study on the evolution of tetrapod skin.

Expression variations in ectodysplasin-A gene (eda) may contribute to morphological divergence of scales in haplochromine cichlids

BackgroundElasmoid scales are one of the most common dermal appendages and can be found in almost all species of bony fish differing greatly in their shape. Whilst the genetic underpinnings behind elasmoid scale development have been investigated, not much is known about the mechanisms involved in moulding of scales. To investigate the links between gene expression differences and morphological divergence, we inferred shape variation of scales from two different areas of the body (anterior and posterior) stemming from ten haplochromine cichlid species from different origins (Lake Tanganyika, Lake Malawi, Lake Victoria and riverine). Additionally, we investigated transcriptional differences of a set of genes known to be involved in scale development and morphogenesis in fish.ResultsWe found that scales from the anterior and posterior part of the body strongly differ in their overall shape, and a separate look on scales from each body part revealed similar trajectories of shape differences considering the lake origin of single investigated species. Above all, nine as well as 11 out of 16 target genes showed expression differences between the lakes for the anterior and posterior dataset, respectively. Whereas in posterior scales four genes (dlx5, eda, rankl and shh) revealed significant correlations between expression and morphological differentiation, in anterior scales only one gene (eda) showed such a correlation. Furthermore, eda displayed the most significant expression difference between species of Lake Tanganyika and species of the other two younger lakes. Finally, we found genetic differences in downstream regions of eda gene (e.g., in the eda-tnfsf13b inter-genic region) that are associated with observed expression differences. This is reminiscent of a genetic difference in the eda-tnfsf13b inter-genic region which leads to gain or loss of armour plates in stickleback.ConclusionThese findings provide evidence for cross-species transcriptional differences of an important morphogenetic factor, eda, which is involved in formation of ectodermal appendages. These expression differences appeared to be associated with morphological differences observed in the scales of haplochromine cichlids indicating potential role of eda mediated signal in divergent scale morphogenesis in fish.

Comparing DNA yield from fish scales following different extraction protocols

Studies on genetic diversity, adaptive potential and fitness of species have become a major tool in conservation biology. These studies require biological material containing a reliable source of DNA which can be extracted and analysed. Recently, non-invasive sampling has become the preferred sampling method of such biological material; particularly when studying endangered species. Elasmoid scales from teleost fish are an example of non-invasive samples from which DNA can successfully be extracted. This study compared different extraction protocols to find an optimal method for extracting DNA from teleost fish scales. This was done with the intent to use the protocol that yielded the highest quantity of DNA on dried, archived scales. The protocols tested in this study included (1) phenol/chloroform with a TNES-urea digestion buffer, (2) phenol/chloroform with an amniocyte digestion buffer and (3) Qiagen DNeasy Blood and Tissue Kit with variations in incubation times and temperatures of each protocol. While the phenol/chloroform with TNES-urea digestion buffer yielded significantly higher concentrations of DNA compared to the other protocols, all protocols followed in this study yielded sufficient quantities of DNA for further downstream applications. Therefore, while there are multiple viable options when selecting a DNA extraction protocol, each research project’s individual needs, requirements and resources need to be carefully considered in order to choose the most effective protocol.

Modeling Bioinspired Fish Scale Designs via a Geometric and Numerical Approach.

Fish scales serve as a natural dermal armor with remarkable flexibility and puncture resistance. Through studying fish scales, researchers can replicate these properties and tune them by adjusting their design parameters to create biomimetic scales. Overlapping scales, as seen in elasmoid scales, can lead to complex interactions between each scale. These interactions are able to maintain the stiffness of the fish’s structure with improved flexibility. Hence, it is important to understand these interactions in order to design biomimetic fish scales. Modeling the flexibility of fish scales, when subject to shear loading across a substrate, requires accounting for nonlinear relations. Current studies focus on characterizing these kinematic linear and nonlinear regions but fall short in modeling the kinematic phase shift. Here, we propose an approach that will predict when the linear-to-nonlinear transition will occur, allowing for more control of the overall behavior of the fish scale structure. Using a geometric analysis of the interacting scales, we can model the flexibility at the transition point where the scales start to engage in a nonlinear manner. The validity of these geometric predictions is investigated through finite element analysis. This investigation will allow for efficient optimization of scale-like designs and can be applied to various applications.

Short-term homeostatic regulation of blood/interstitial fluid Ca2+ concentration by the scales of anadromous sea trout Salmo trutta L. during smoltification and migration.

The elasmoid scales of anadromous sea trout Salmo trutta L. represent a significant internal reservoir of Ca2+ . Although more is known about long-term remodelling of scales in response to calciotropic challenges encountered during smoltification and migration, very little is known about the contribution made by scales to the short-term, minute-to-minute regulation of Ca2+ homeostasis in the extracellular fluid (ECF) during these phases of the life cycle. This gap in the knowledge is partly due to the technical challenges involved in measuring small Ca2+ fluxes around the scales of live fish in real time. Here, this study describes exfoliating, mounting and culturing scales and their resident cells from parr, smolt and adult sea trout from a freshwater environment, as well as from adult sea trout caught in sea or brackish water. All the scales were then examined using an extracellular, non-invasive, surface-scanning Ca2+ -sensitive microelectrode. The authors quantified the Ca2+ fluxes, in the absence of any systemic or local regulators, into and out of scales on both the episquamal and hyposquamal sides under different extracellular calcemic challenges set to mimic a variety of ECF-Ca2+ concentrations. Scales from the life-cycle stages as well as from adult fish taken from sea, brackish or fresh water all showed a consistent efflux or influx of Ca2+ under hypo- or hypercalcemic conditions, respectively. What were considered to be isocalcemic conditions resulted in minimal flux of Ca2+ in either direction, or in the case of adult scales, a consistent but small influx. Indeed, adult scales appeared to display the largest flux densities in either direction. These new data extend the current understanding of the role played by fish scales in the short-term, minute-to-minute homeostatic regulation of ECF-Ca2+ concentration, and are similar to those recently reported from zebrafish Danio rerio scales. This suggests that this short-term regulatory response might be a common feature of teleost scales.

Structure and Mechanical Adaptability of a Modern Elasmoid Fish Scale from the Common Carp

Summary The carp (Cyprinus carpio) has typical elasmoid scales commonly found on teleosts. They provide protection while retaining flexibility and maneuverability of the fish. The exterior surface of the scale consists of an ultrathin discontinuous mineral layer on top of mineralized woven collagen fibrils. The underlying foundation is composed of two collagenous components. The major one consists of a single-twisted “Bouligand” structure with a twisting angle of 36°. A secondary “sheet-like” structure, formed by thinner collagen fibrils oriented along the thickness direction, acts to increase the integrity of the scale. Here, we identify the deformation and failure mechanisms of the carp scale, revealing slight tensile anisotropy. Using in situ small-angle X-ray scattering during tensile testing, the toughening mechanisms of the scale, including the adaptive structural reorientation of lamellae as well as fibrillar sliding and elastic deformation, are quantified and compared with those of other fish scales.

Tango with the Piranhas

Coexisting with fish known by their fiercely predaceous behaviors has driven the Arapaimas gigas to develop one of the toughest protective layers known in nature, their elasmoid scales. In this work, Yang et al. demonstrated what mechanisms lead to such remarkable toughness.

Arapaima Fish Scale: One of the Toughest Flexible Biological Materials

Summary For fish scales to provide protection from predators without severely compromising mobility, they must be lightweight, flexible, and tough. The arapaima fish scale is a superb example of this, enabling its survival in piranha-infested lakes of the Amazon. These elasmoid scales comprise two layers: a laminate composite of parallel collagen fibrils arranged in a Bouligand-like pattern and a highly mineralized surface layer that prevents initial penetration damage. Here, we measure its J-integral fracture toughness and find that the crack-growth toughness is ∼100–200 kJ⋅m−2, representing a very high fracture resistance for a natural material. This toughness results from multiple deformation mechanisms acting in concert in the twisted plywood structure of the scale, involving the collagenous lamellae at varying orientations retarding crack advance through stretching, reorientation, delamination and shear, and fracture. The toughness values obtained for the arapaima scales indicate that they are among the toughest of nature's flexible biological materials.

Assessing the ability of zebrafish scales to contribute to the short-term homeostatic regulation of [Ca2+] in the extracellular fluid during calcemic challenges

The elasmoid scales of fish represent a significant internal reservoir of calcium ions (Ca2+), but little is known about the contribution of these scales to the short-term regulation of Ca2+ homeostasis in the extracellular fluid (ECF). This gap in our knowledge is partly due to the technical challenges involved in measuring small Ca2+ fluxes around the scales of live fish in real time. Here, we describe a technique for exfoliating, mounting, and culturing intact living zebrafish Danio rerio scales, then subjecting them to examination using an extracellular, non-invasive, surface-scanning ion-selective electrode technique (SIET). In a Ca2+-sensitive configuration, the SIET can resolve Ca2+ flux values in the low-to-sub picomole/square centimeter/second range, with a spatial resolution of approximately 5 μm. We quantified the Ca2+ fluxes into and out of scales under different extracellular calcemic challenges set to mimic a variety of Ca2+ concentrations in the ECF and showed that the results were similar to those previously reported from isolated mouse metatarsal bone. Our new data extend our current understanding of the role played by fish scales in the short-term homeostatic regulation of Ca2+ concentration in the ECF. They also support the suggestion that scales might provide an inexpensive and complementary model for studying the fundamentals of bone-mediated homeostatic Ca2+ regulation and the diseases that result from its dysregulation.

Hyperelastic phase-field fracture mechanics modeling of the toughening induced by Bouligand structures in natural materials

Bouligand structures are widely observed in natural materials; elasmoid fish scales and the exoskeleton of arthropods, such as lobsters, crabs, mantis shrimp and insects, are prime examples. In fish scales, such as those of the Arapaima gigas, the tough inner core beneath the harder surface of the scale displays a Bouligand structure comprising a layered arrangement of collagen fibrils with an orthogonal or twisted staircase (or plywood) architecture. A much rarer variation of this structure, the double-twisted Bouligand structure, has been discovered in the primitive elasmoid scales of the coelacanth fish; this architecture is quite distinct from “modern” elasmoid fish scales yet provides extraordinary resistance to deformation and fracture. Here we examine the toughening mechanisms created by the double-twisted Bouligand structure in comparison to those generated by the more common single Bouligand structures. Specifically, we have developed an orientation-dependent, hyperelastic, phase-field fracture mechanics method to computationally examine the relative fracture toughness of elasmoid fish scales comprising single vs. double-twisted Bouligand structures of fibrils. The model demonstrates the critical role played by the extra inter-bundle fibrils found in coelacanth fish scales in enhancing the toughness of Bouligand-type structures. Synthesis and fracture tests of 3-D printed Bouligand-type materials are presented to support the modeling and complement our understanding of the fracture mechanisms in Bouligand-type structures.

Arapaima Fish Scale: One of the Toughest Flexible Biological Materials

In order for fish scales to provide protection from predators without significantly compromising mobility, they have to be lightweight, flexible and tough. The Arapaima fish scale is a superb example of these properties, which enable survival in piranha-infested seasonal lakes of the Amazon. These elasmoid scales are composed of two layers: a laminate composite of parallel collagen fibrils arranged in a Bouligand-like pattern, and a hard, highly mineralized surface layer that prevents initial penetration damage. We measure here the J-integral based fracture toughness of the scale and find that the crack-growth toughness as high as ~200 kJ⋅m-2, representing a very high fracture resistance for a flexible biological material. This toughness is primarily the result of multiple mechanisms of deformation acting in concert in the twisted plywood structure of the scale, involving the collagen lamellae at varying orientations controlling crack advance through stretching, rotation, delamination and shear, and finally fracture. These toughening mechanisms operate in sequence at the crack tip, retarding its advance in a most effective manner. The toughness values obtained for the Arapaima scales indicate that they are among the toughest of nature’s flexible biological materials.

Novel Defense Mechanisms in the Armor of the Scales of the “Living Fossil” Coelacanth Fish

AbstractHere, experiments and analysis revealing the unique defense mechanisms of the coelacanth, a lobe‐finned fish termed a “living fossil”, are reported, as it was considered to be extinct until 1938, but extant for 400 million years. This defense is provided by primitive elasmoid scales having a rare double‐twisted Bouligand structure of lamellae which provides extraordinary resistance to deformation without failure. Distinct from other elasmoid scales, the collagen fibrils in the coelacanth fish scales form bundles which are embedded in a matrix comprising fibers arranged perpendicular to the layered (double‐twisted Bouligand) structure that provide added rigidity and resistance to deformation. Using in situ synchrotron small‐angle X‐ray scattering during uniaxial tensile testing, the deformation mechanisms of the collagen are identified in terms of fibril stretching, reorientation, sliding, bending, and delamination. The unique structure of the coelacanth scales, distinct from modern elasmoid scales such as the carp, provides a variety of mechanisms to arrest cracking, making it an outstanding damage‐tolerant material to resist predator attacks.

Genetic analyses in Lake Malawi cichlids identify new roles for Fgf signaling in scale shape variation

Elasmoid scales are the most common epithelial appendage among vertebrates, however an understanding of the genetic mechanisms that underlie variation in scale shape is lacking. Using an F2 mapping cross between morphologically distinct cichlid species, we identified >40 QTL for scale shape at different body positions. We show that while certain regions of the genome regulate variation in multiple scales, most are specific to scales at distinct positions. This suggests a degree of regional modularity in scale development. We also identified a single QTL for variation in scale shape disparity across the body. Finally, we screened a QTL hotspot for candidate loci, and identified the Fgf receptor fgfr1b as a prime target. Quantitative rtPCR and small molecule manipulation support a role for Fgf signaling in shaping cichlid scales. While Fgfs have previously been implicated in scale loss, these data reveal new roles for the pathway in scale shape variation.

Benzo(a)pyrene reduces osteoclast and osteoblast activity in ex-vivo scales of zebrafish (Danio rerio[Hamilton-Buchanan, 1822]) and goldfish (Carassius auratus[Linnaeus, 1758

Environmental contaminants have previously been demonstrated to cause bone deformities mediated through the aryl hydrocarbon receptor (AhR) in fish and mammals. Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous in the environment, many of them capable of activating AhR. In the present study, fish scales were utilized as a model system to examine possible AhR‐mediated effects of PAHs on bone forming osteoblasts and bone resorptive osteoclasts, using the AhR‐ligand benzo(a)pyrene (BaP) as a model compound. Elasmoid scales from goldfish and zebrafish were exposed to 0.005–50 μM BaP for up to 48 hr, and the activity of osteoblastic and osteoclastic markers were measured, as well as mRNA levels of bone related genes and cyp1a and cyp3a. Using the sp7:luciferase zebrafish assay, a decrease in sp7 promoter activation was observed at the two highest concentrations (5 and 50 μM). Gelatin zymography revealed significantly reduced activity of the osteoclastic protease matrix metalloproteinase 9 (Mmp9) at the highest concentration. Furthermore, transcriptional analysis showed a dose‐dependent increase in cyp1a, however, no significant differential expression was observed for the bone related genes. The findings indicate that BaP might decrease differentiation and activation of osteoblasts, and reduce osteoclastic activity, and thus ultimately cause decreased bone formation. Further investigation is necessary in order to confirm the role of AhR in mediating these effects.

The design and assessment of bio-inspired additive manufactured stab-resistant armour

ABSTRACTThe performance of modern fibre-based or polycarbonate armour has significantly improved since their introduction, providing protection against a range of low- and high-velocity threats. While this is so, users of such armour frequently report of issues relating to their operational suitability resulting in impaired performance and physiological effects. Recently, researchers have focused on how naturally occurring protective mechanisms could be utilised to enhance the protective and operational performance of wearers of engineered body armour. The research presented within this paper therefore utilises a series of key design characteristics exhibited within naturally occurring elasmoid scale armour, coupled with established laser sintering manufacturing parameters, for the realisation and assessment of a scale-based stab-resistant armoured structure to internationally recognised test standards.