Calcidermoid Scales: Proposal for a New Primary Fish Scale Category, Division into Types, Their Origin, Relation to Elasmoid Scales, and Taxonomic Distribution

The trunk canal of fishes is contained within a series of lateral line (LL) scales. To categorise LL scale structural types, and determine their distribution, an analysis of original data was undertaken using light and scanning electron microscopy in combination with a literature survey from over 1,000 species representative of most orders of bony fishes. Our categorisation of LL scales is based on the relationship between the tube, or ossified trunk canal segment, and associated scale. Tubular‐Scalar LL scales consist of a distinguishable tube and elasmoid scale in scale pockets. Four types occur only in species with elasmoid scales. Integrated LL scales do not develop in scale pockets, and their tube is enclosed or extended by a non‐elasmoid scale or spines. Integrated 1 and 2 LL scales co‐occur with ganoid and calcidermoid scales, and Integrated 3 LL scales occur when common scales are absent or elasmoid. Tubular LL scales are tubes only, occurring mainly in scaleless species or with calcidermoid and elasmoid scales. Non‐Tubular LL scales are composed only of a scale, co‐occurring mainly with cycloid scales. There is consistency of LL scale type in many orders, families and genera and the presence of different types within taxa can be meaningful.

The present paper summarizes recent results dealing with the development and structure of the scales in the actinopterygian fishes and presents a new phylogenetical interpretation of the routes leading from the ancestral thick ganoid scales to the modern thin elasmoid ones. The different regions constituting the ganoid (ganoine, dentine and osseous basal plate) and elasmoid (Limiting layer, External layer and isopedine) scales are compared in view of possible homologies. The outer Limiting layer of the elasmoid scale is not ganoine, but some common features lead us to suggest that ganoine and the outer Limiting layer might be closer than generally admitted. On the other hand, the study of the development of the ganoid scales in polypterids has undoubtedly shown that the very young ganoid scales arc in fact elasmoid ones. It is concluded that the elasmoid scales of the actinopterygian fishes are derived from the ancestral ganoid scales by a process of paedomorphosis and that the osseous basal plate, and probably the dentine have not been retained in the elasmoid scales.

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.

Comparative studies on scale structure and development in bony fish have led to the hypothesis that elasmoid scales in teleosts could be dental in origin. The present work was undertaken to determine whether the scales in zebrafish (Danio rerio), a species widely used in genetics and developmental biology, would be an appropriate focus for further studies devoted to the immunodetection of dental components or to the detection of the expression of genes coding for various dental proteins in fish scales. The superficial region of mature and experimentally regenerated scales and its relationships to the epidermal cover were studied in adult zebrafish using scanning (SEM) and transmission (TEM) electron microscopy. The elasmoid scales are relatively large, thin, and are located in the upper region of the dermis, close to the epidermis. In adults, the surface of the posterior region appears smooth at the SEM level and is entirely covered by the epidermis. During regeneration, the relationship of the epidermal cover to the scale surface is established within 4 days. This interface is easier to study in regenerating than in mature scales because the former are poorly mineralized. TEM revealed that: (1) the epidermis is in direct contact with the scale surface, from which it is separated only by a basement membrane-like structure, (2) there are no dermal elements at the scale surface except at the level of grooves issuing from the focus and crossing the scale surface radially, (3) the mineral crystals located in this superficial region are perpendicular to the scale surface, whereas those located deeper within the collagenous scale matrix are randomly disposed, and (4) when decalcified, the matrix of the superficial region of the scale appears devoid of collagen fibrils but contains thin electron-dense granules, some of which are arranged into layers. The continuous epidermal covering, the absence of dermal elements, as well as the fine structure of the matrix and its type of mineralization, strongly suggest that epidermal products, possibly enamel-like proteins, are deposited at the scale surface and contribute to the thickening of the upper layer in zebrafish scales. J. Morphol. 231:161-174, 1997. © 1997 Wiley-Liss, Inc.

REVIEW QUESTION / OBJECTIVE What is the effectiveness of strategies and interventions to manage acute pain in patients who are identified as having a tolerance to or dependence on opioids? The objective of the review is to establish the effectiveness of pharmacological and non-pharmacological strategies and interventions to manage acute pain in patients who are identified as having a tolerance to or dependence on opioids. INCLUSION CRITERIA Types of participants This review will consider studies that include patients over the age of 18 years who have presented to a hospital or health care facility requiring management for acute pain, and are identified within the studies as having a dependence or tolerance to opioids. This includes but is not limited to patients with a history of: Dependence or tolerance of opioids Recreational opioid use Substance addiction Opioid replacement therapy. Patients may have a history of chronic pain or cancer pain; however the pain being treated must also be classified as new in diagnosis and not an increase of pre-existing pain. Patients who are classified as palliative will be excluded from the systematic review. Types of intervention(s) This review will consider studies that focus on interventions and strategies aimed at effectively managing acute pain in opioid tolerant patients. Interventions and strategies may include but are not limited to: Types/combinations of analgesia which may include: morphine, semisynthetic derivatives such as oxycodone and hydromorphone and totally synthetic derivatives such as fentanyl and methadone. Combinations of opioids and non-opioids; non-opioids will also be considered Patient TRUNCATED AT 250 WORDS

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.

Recycling of secondary fish resources is an important task for the organization of efficient and environmentally friendly production, taking into account the principle of resource conservation. To develop a comprehensive technology for processing fish scales, an in-depth and complete study of its types, chemical composition and dimensional and mass characteristics is necessary. It has been established that the scales of the fish of the Astrakhan region are represented by two types: ganoid (in sturgeon) and elasmoid (in most commercial and pond fish). Elasmoid scales are divided into cycloid and ctenoid. The ctenoid scales (in walleye, perch and pike) have outgrowths, which give it a roughness. Such scales are usually smaller than cycloid scales. The average size of the scales of fish in the Astrakhan region varies from 6.7 to 20.5 mm, the largest size is noted in white amur (20.5 mm), carp (18.9 mm) and carp (18.8 mm), the smallest in walleye (6.7 mm) and perch (7.1 mm). The average thickness of the scales varies from 79 microns (silver carp) to 942 microns (sturgeon). The mass yield of scales from whole fish ranges from 0.4% (sturgeon) and from 2.4 to 8.0% in representatives of the elasmoid type. The content of nitrogen-containing substances in the scales of the studied fish varies from 43.2% in perch to 68.7% in carp, the alkali-soluble protein fraction was found from 16.7% (sturgeon) to 58.4% (silver carp). In addition to the target component, impurities of water- and salt-soluble proteins, minerals and various pigments (chromatophores) were found in the scales, which must be separated in the technological process. As a result of the research, the classification of fish scales of the Astrakhan region by chemical composition has been compiled, taking into account the prospects for protein extraction. These studies are fundamental for creating integrated technological solutions for processing fish scales to obtain a wide range of food and feed products.

Immunofluorescence and electron microscopy were used to analyze the relationships between the organization of collagen fibrils in elasmoid scales, and the orientation of microtubules and actin microfilaments in the scleroblasts producing this collagenous stroma. Attention was focused on the basal plate of the scales because of the highly ordered three-dimensional arrangement of the collagen fibrils in superimposed plies forming an acellular plywood-like structure. The collagen fibrils are synthesized by the scleroblasts forming a monolayered pseudo-epithelium, the hyposquama, at the lowest surface of the scale. Fully developed scales with a low collagen deposition rate were compared with regenerating scales active in fibrillogenesis. When an ordered array of the collagen fibrils is found, the innermost collagen fibrils are coaligned with microtubules and actin microfilaments. Thus, because of this coalignment, microtubules and actin microfilaments of the hyposquamal scleroblasts are subjected to consecutive alterations during the formation of the plies of the basal plate. The sequence of events when the collagen fibrils change their direction from one ply to the other in the basal plate is deduced from immunofluorescence and phase-contrast-microscopic observations. During the formation of the orthogonal plywood-like structure in the regenerating scales, first microtubules may change their curse with a rotating angle of about 90 degrees; then, actin microfilaments are disorganized and reorganized by interacting mechanically with the microtubules with which they are coaligned. Collagen fibrils are synthesized in a direction that is roughly perpendicular to that of the preceding ply. The unknown signals inducing the change in direction of the cytoskeleton may be transmitted throughout the hyposquama via gap junctions.

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.

In the first part of this paper we review current knowledge regarding fish scales, focusing on elasmoid scales, the only type found in two model species, the zebrafish and the medaka. After reviewing the structure of scales and their evolutionary origin, we describe the formation of the squamation pattern. The regularity of this process suggests a pre-patterning of the skin before scale initiation. We then summarise the dynamics of scale development on the basis of morphological observations. In the absence of molecular data, these observations support the existence of genetic cascades involved in the control of scale development. In the second part of this paper, we illustrate the potential that scale development offers as a model to study organogenesis mediated by epithelial-mesenchymal interactions. Using the zebrafish (Danio rerio), we have combined alizarin red staining, light and transmission electron microscopy and in situ hybridisation using an anti-sense RNA probe for the sonic hedgehog (shh) gene. Scales develop late in ontogeny (30 days post-fertilisation) and close to the epidermal cover. Only cells of the basal epidermal layer express shh. Transcripts are first detected after the scale papillae have formed. Thus, shh is not involved in the mechanisms controlling squamation patterning and scale initiation. As the scales enlarge, shh expression is progressively restricted to a subset of basal epidermal cells located in the region that overlies their posterior field. This pattern of expression suggests that shh may be involved in the control of scale morphogenesis and differentiation in relationship with the formation of the epidermal fold in the posterior region.

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.

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.

Paleogene paleoclimate reconstruction using oxygen isotopes from land and freshwater organisms: the use of multiple paleoproxies

The possibility of using separate signs of microstructure of skin derivatives to understand phylogenesis processes at various hierarchical levels on the example of elasmoid scale of bony fish, feathers of Paleognathae birds, hepatoid glands, and mammal hair was demonstrated and discussed. It was shown that (1) the presence of toothed sclerite growths on the surface of the elasmoid scale of bony fish provided with a central canal can serve as a proof of the evolutional relation of placoid and elasmoid scales; (2) particularities of the microstructure of feathers of Paleognathae birds accord with the branching of their phylogenetic tree; (3) the development of hepatoid glands suggests a phylogenetic relatedness of ancestor forms of cavicorns, Canidae, and Felidae; (4) the subtle construction of horse hair shows the succession of the ancient E. lenensis and northern aborigine breeds of the domestic horse, the direction of the historical process of horse domestication and adaptation of these animals to environmental conditions; (5) similarities in the microstructure of hair of the giant and red panda and bears indicate their evolutional links with Ursidae rather than raccoons.

Wilcoxon-Mann-Whitney odds ratio: A statistical measure for ordinal outcomes such as EDSS