Laminar Pattern Research Articles

Blood flow characteristics after aortic valve neocuspidization in paediatric patients: a comparison with the Ross procedure.

AimsThe aortic valve (AV) neocuspidization (Ozaki procedure) is a novel surgical technique for AV disease that preserves the natural motion and cardiodynamics of the aortic root. In this study, we sought to evaluate, by 4D-flow magnetic resonance imaging, the aortic blood flow characteristics after AV neocuspidization in paediatric patients.Methods and resultsAortic root and ascending aorta haemodynamics were evaluated in a population of patients treated with the Ozaki procedure; results were compared with those of a group of patients operated with the Ross technique. Cardiovascular magnetic resonance studies were performed at 1.5 T using a 4D flow-sensitive sequence acquired with retrospective electrocardiogram-gating and respiratory navigator. Post-processing of 4D-flow analysis was performed to calculate flow eccentricity and wall shear stress. Twenty children were included in this study, 10 after Ozaki and 10 after Ross procedure. Median age at surgery was 10.7 years (range 3.9–16.5 years). No significant differences were observed in wall shear stress values measured at the level of the proximal ascending aorta between the two groups. The analysis of flow patterns showed no clear association between eccentric flow and the procedure performed. The Ozaki group showed just a slightly increased transvalvular maximum velocity.ConclusionProximal aorta flow dynamics of children treated with the Ozaki and the Ross procedure are comparable. Similarly to the Ross, Ozaki technique restores a physiological laminar flow pattern in the short-term follow-up, with the advantage of not inducing a bivalvular disease, although further studies are warranted to evaluate its long-term results.

Laminar non-premixed flame patterns in compact micro disc-combustor with annular step and radial preheated channel

The study presents the laminar methane-air non-premixed flame patterns under the synergistic effect of heat and flow recirculation in a radial microchannel, as obtained through a numerical simulation. A regime diagram of the flame behaviors for various operating conditions was obtained. It was observed that the flame always remained stable until it was extinguished, which implies that the flame stability was strong. In addition, the flame patterns at small, moderate, and large Reynolds numbers (Re) were revealed. For a small Re, the flame could be well-anchored in a very upstream channel at a large global equivalence ratio (ϕ). At a moderate ϕ, the upstream part of the flame was anchored by a minor recirculation zone (RZ) near the inlet of the combustion chamber. At a small ϕ (i.e., 0.6), the flame became completely flat, and its upstream part was anchored by the major RZ behind the annular step. For a moderate Re, the flame roots were remarkably anchored by the minor and/or major RZs. For a large Re, for the first time. It was observed that the whole stable flame split into two parts in the radial channel at ϕ = 0.8 and 0.7, namely the upstream minor flame engulfed in the minor RZ and the downstream major flame anchored by the major RZ. However, when ϕ was further decreased to 0.6, the minor flame was extinguished and only the large major flame existed. The transformation mechanism of the aforementioned flame behaviors was also revealed in detail. Furthermore, this study has yielded abundant information on flame patterns in the current radial microchannel with the annular step and the radial preheated channel, which could help us gain further insights into the flame propagation characteristics in a radial channel.

Glial Response and Neuroinflammation in Cerebrocortical Atrophy in a Young Irish Wolfhound Dog

Simple SummaryNeuroinflammation is considered a reaction of the nervous system itself to protect and repair structural changes developed in it. Despite its initial positive purpose, sometimes it can produce worse consequences for the tissue. In this article, we present a case of an Irish Wolfhound dog suffering a rare idiopathic neurodegenerative disease producing wide cerebral cortical damage with loss of neuronal bodies in a bilateral and symmetrical pattern. We have studied the glial components of the neuroinflammation developed describing how they have exacerbated the nervous tissue damage.A two-year-old, Irish Wolfhound dog presented with a history of progressive neurological signs. Neurological exam revealed disorientation, absence of menace response, reduction of right nasal sensation, hypermetria and ataxia with reduction of proprioception in all four limbs. MRI findings were compatible with laminar neuronal necrosis and possible bilateral cortical cerebral atrophy. Grossly, a severe bilateral reduction of the gray matter with flattening of gyri, mainly in frontal and parietal cerebral areas, was observed. Histologically, multiple, segmental, bilateral, and symmetric areas of neuronal loss, necrosis and degeneration, in a laminar pattern, associated with a reactive gliosis were observed. Immunohistochemical studies showed severe reduction of neuronal bodies, proliferation and hypertrophy of astrocytes and microglia. Few perivascular B and T cells were demonstrated. Based on these data, we show some of the neuroinflammatory events that occur during CNS repair in a chronic phase of this condition.

Laminar Origin of Corticostriatal Projections to the Motor Putamen in the Macaque Brain.

In the macaque brain, projections from distant, interconnected cortical areas converge in specific zones of the striatum. For example, specific zones of the motor putamen are targets of projections from frontal motor, inferior parietal, and ventrolateral prefrontal hand-related areas and thus are integral part of the so-called "lateral grasping network." In the present study, we analyzed the laminar distribution of corticostriatal neurons projecting to different parts of the motor putamen. Retrograde neural tracers were injected in different parts of the putamen in 3 Macaca mulatta (one male) and the laminar distribution of the labeled corticostriatal neurons was analyzed quantitatively. In frontal motor areas and frontal operculum, where most labeled cells were located, almost everywhere the proportion of corticostriatal labeled neurons in layers III and/or VI was comparable or even stronger than in layer V. Furthermore, within these regions, the laminar distribution pattern of corticostriatal labeled neurons largely varied independently from their density and from the projecting area/sector, but likely according to the target striatal zone. Accordingly, the present data show that cortical areas may project in different ways to different striatal zones, which can be targets of specific combinations of signals originating from the various cortical layers of the areas of a given network. These observations extend current models of corticostriatal interactions, suggesting more complex modes of information processing in the basal ganglia for different motor and nonmotor functions and opening new questions on the architecture of the corticostriatal circuitry.SIGNIFICANCE STATEMENT Projections from the ipsilateral cerebral cortex are the major source of input to the striatum. Previous studies have provided evidence for distinct zones of the putamen specified by converging projections from specific sets of interconnected cortical areas. The present study shows that the distribution of corticostriatal neurons in the various layers of the primary motor and premotor areas varies depending on the target striatal zone. Accordingly, different striatal zones collect specific combinations of signals from the various cortical layers of their input areas, possibly differing in terms of coding, timing, and direction of information flow (e.g., feed-forward, or feed-back).

Distinct Laminar and Cellular Patterns of GABA Neuron Transcript Expression in Monkey Prefrontal and Visual Cortices.

The functional output of a cortical region is shaped by its complement of GABA neuron subtypes. GABA-related transcript expression differs substantially between the primate dorsolateral prefrontal cortex (DLPFC) and primary visual (V1) cortices in gray matter homogenates, but the laminar and cellular bases for these differences are unknown. Quantification of levels of GABA-related transcripts in layers 2 and 4 of monkey DLPFC and V1 revealed three distinct expression patterns: 1) transcripts with higher levels in DLPFC and layer 2 [e.g., somatostatin (SST)]; 2) transcripts with higher levels in V1 and layer 4 [e.g., parvalbumin (PV)], and 3) transcripts with similar levels across layers and regions [e.g., glutamic acid decarboxylase (GAD67)]. At the cellular level, these patterns reflected transcript- and cell type-specific differences: the SST pattern primarily reflected differences in the relative proportions of SST mRNA-positive neurons, the PV pattern primarily reflected differences in PV mRNA expression per neuron, and the GAD67 pattern reflected opposed patterns in the relative proportions of GAD67 mRNA-positive neurons and in GAD67 mRNA expression per neuron. These findings suggest that differences in the complement of GABA neuron subtypes and in gene expression levels per neuron contribute to the specialization of inhibitory neurotransmission across cortical circuits.

3D hydrogels reveal medulloblastoma subgroup differences and identify extracellular matrix subtypes that predict patient outcome.

Medulloblastoma (MB) is the most common malignant brain tumour in children and is subdivided into four subgroups: WNT, SHH, Group 3, and Group 4. These molecular subgroups differ in their metastasis patterns and related prognosis rates. Conventional 2D cell culture methods fail to recapitulate these clinical differences. Realistic 3D models of the cerebellum are therefore necessary to investigate subgroup‐specific functional differences and their role in metastasis and chemoresistance. A major component of the brain extracellular matrix (ECM) is the glycosaminoglycan hyaluronan. MB cell lines encapsulated in hyaluronan hydrogels grew as tumour nodules, with Group 3 and Group 4 cell lines displaying clinically characteristic laminar metastatic patterns and levels of chemoresistance. The glycoproteins, laminin and vitronectin, were identified as subgroup‐specific, tumour‐secreted ECM factors. Gels of higher complexity, formed by incorporation of laminin or vitronectin, revealed subgroup‐specific adhesion and growth patterns closely mimicking clinical phenotypes. ECM subtypes, defined by relative levels of laminin and vitronectin expression in patient tissue microarrays and gene expression data sets, were able to identify novel high‐risk MB patient subgroups and predict overall survival. Our hyaluronan model system has therefore allowed us to functionally characterize the interaction between different MB subtypes and their environment. It highlights the prognostic and pathological role of specific ECM factors and enables preclinical development of subgroup‐specific therapies. © 2020 The Authors. The Journal of Pathology published by John Wiley & Sons, Ltd. on behalf of The Pathological Society of Great Britain and Ireland.

The effect of diffusion on mass transfer in a laminar falling film: Observation versus theory

When a gas is dissolved into a liquid, the mass transport at the gas-liquid interface depends on many factors including the gas and liquid properties and hydrodynamics. The mass transport of a gas through the liquid is a limiting step in many chemical reactions. To gain a fundamental understanding of multiphase interfaces, the rate of mass transfer has been measured for pure gases (H2, N2, O2, and He) into a thin liquid film with a well-defined surface area and velocity profile. A gravity-driven falling film of liquid with a thickness in the range of 175 to 198 × 10−6 m was contacted with a gas phase inside a closed system. The liquid was circulated continuously and the pressure in the closed system was observed until it was saturated with gas and the equilibrium pressure was reached. In this device, a laminar flow pattern is observed, and therefore, the geometry and hydrodynamics of the liquid film are well defined. This enables the mass transfer rate to be broken down into two parameters; one which is the gas-liquid interfacial area (a), and a second parameter, which is the mass transfer coefficient (kL). Using gases with varying diffusion coefficients enables a comparison of the measured rates of mass transport to the rates predicted by film theory, penetration theory, and Danckwerts’s surface renewal theory.

Brain connectomes come of age.

Databases of consistent, directed- and weighted inter-areal connectivity for mouse, macaque and marmoset monkeys have recently become available and begun to be used to build structural and dynamical models. A structural hierarchy can be defined based by laminar patterns of cortical connections. A large-scale dynamical model of the macaque cortex endowed with a laminar structure accounts for empirically observed frequency-modulated interplay between bottom-up and top-down processes. Signal propagation in the model with spiking neurons displays a threshold of stimulus amplitude for the activity to gain access to the prefrontal cortex, reminiscent of the ignition phenomenon associated with conscious perception. These two examples illustrate how connectomics inform structurally based dynamic models of multi-regional brain systems. Theory raises novel questions for future anatomical and physiological empirical research, in a back-and-forth collaboration between experimentalists and theorists. Directed- and weighted inter-areal cortical connectivity matrices of macaque, marmoset and mouse exhibit similarities as well as marked differences. The new connectomic data provide quantitative information for structural and dynamical modeling of multi-regional cortical circuit providing insight to the global cortical function. Quantification of cortical hierarchy guides investigations of interplay between bottom-up and top-down information processes.

The laminar profile of sleep spindles in humans

Sleep spindles are functionally important NREM sleep EEG oscillations which are generated in thalamocortical, corticothalamic and possibly cortico-cortical circuits. Previous hypotheses suggested that slow and fast spindles or spindles with various spatial extent may be generated in different circuits with various cortical laminar innervation patterns. We used NREM sleep EEG data recorded from four human epileptic patients undergoing presurgical electrophysiological monitoring with subdural electrocorticographic grids (ECoG) and implanted laminar microelectrodes penetrating the cortex (IME). The position of IMEs within cortical layers was confirmed using postsurgical histological reconstructions. Many spindles detected on the IME occurred only in one layer and were absent from the ECoG, but with increasing amplitude simultaneous detection in other layers and on the ECoG became more likely. ECoG spindles were in contrast usually accompanied by IME spindles. Neither IME nor ECoG spindle cortical profiles were strongly associated with sleep spindle frequency or globality. Multiple-unit and single-unit activity during spindles, however, was heterogeneous across spindle types, but also across layers and patients. Our results indicate that extremely local spindles may occur in any cortical layer, but co-occurrence at other locations becomes likelier with increasing amplitude and the relatively large spindles detected on ECoG channels have a stereotypical laminar profile. We found no compelling evidence that different spindle types are associated with different laminar profiles, suggesting that they are generated in cortical and thalamic circuits with similar cortical innervation patterns. Local neuronal activity is a stronger candidate mechanism for driving functional differences between spindles subtypes.

Multimodal 3D atlas of the macaque monkey motor and premotor cortex

In the present study we reevaluated the parcellation scheme of the macaque frontal agranular cortex by implementing quantitative cytoarchitectonic and multireceptor analyses, with the purpose to integrate and reconcile the discrepancies between previously published maps of this region.We applied an observer-independent and statistically testable approach to determine the position of cytoarchitectonic borders. Analysis of the regional and laminar distribution patterns of 13 different transmitter receptors confirmed the position of cytoarchitectonically identified borders. Receptor densities were extracted from each area and visualized as its “receptor fingerprint”. Hierarchical and principal components analyses were conducted to detect clusters of areas according to the degree of (dis)similarity of their fingerprints. Finally, functional connectivity pattern of each identified area was analyzed with areas of prefrontal, cingulate, somatosensory and lateral parietal cortex and the results were depicted as “connectivity fingerprints” and seed-to-vertex connectivity maps.We identified 16 cyto- and receptor architectonically distinct areas, including novel subdivisions of the primary motor area 4 (i.e. 4a, 4p, 4m) and of premotor areas F4 (i.e. F4s, F4d, F4v), F5 (i.e. F5s, F5d, F5v) and F7 (i.e. F7d, F7i, F7s). Multivariate analyses of receptor fingerprints revealed three clusters, which first segregated the subdivisions of area 4 with F4d and F4s from the remaining premotor areas, then separated ventrolateral from dorsolateral and medial premotor areas. The functional connectivity analysis revealed that medial and dorsolateral premotor and motor areas show stronger functional connectivity with areas involved in visual processing, whereas 4p and ventrolateral premotor areas presented a stronger functional connectivity with areas involved in somatomotor responses.For the first time, we provide a 3D atlas integrating cyto- and multi-receptor architectonic features of the macaque motor and premotor cortex. This atlas constitutes a valuable resource for the analysis of functional experiments carried out with non-human primates, for modeling approaches with realistic synaptic dynamics, as well as to provide insights into how brain functions have developed by changes in the underlying microstructure and encoding strategies during evolution.

Pathways for Contextual Memory: The Primate Hippocampal Pathway to Anterior Cingulate Cortex.

The anterior cingulate cortex (ACC) is one of the few prefrontal areas that receives robust direct hippocampal terminations. This pathway may enable current context and past experience to influence goal-directed actions and emotional regulation by prefrontal cortices. We investigated the still ill-understood organization of the pathway from anterior hippocampus to ACC (A24a, A25, A32) to identify laminar termination patterns and their postsynaptic excitatory and inhibitory targets from system to synapse in rhesus monkeys. The densest hippocampal terminations targeted posterior A25, a region that is involved in affective and autonomic regulation. Hippocampal terminations innervated mostly excitatory neurons (~90%), suggesting strong excitatory effects. Among the smaller fraction of inhibitory targets, hippocampal terminations in A25 preferentially innervated calretinin neurons, a pattern that differs markedly from rodents. Further, hippocampal terminations innervated spines with D1 receptors, particularly in the deep layers of A25, where D1 receptors are enriched in comparison with the upper layers. The proximity of hippocampal terminations to D1 receptors may enable dopamine to enhance information transfer from the hippocampus to A25 and contribute to dopaminergic influence downstream on goal-directed action and emotional control by prefrontal cortices, in processes that may be disrupted by excessive dopamine release during uncontrollable stress.

The laminar pattern of resting state in human cerebral cortex

Resting state functional Magnetic Resonance Imaging (RS-fMRI) provides the means to measure neuronal activity. One of the most commonly used methods to explore the RS-fMRI signal is the Probabilistic Independent Component Analysis (PICA). PICA allows to depict brain functional connectivity (FC) networks. Yet most of the IC maps obtained with this method do not represent any particular FC network. Consequently, those IC maps are classified as artifacts or noise of an unknown source. We hypothesized that the unexplained RS-fMRI signal patterns that are picked up by the PICA can be related to the differences in oxygen metabolism and blood flow in cortical layers. This study aimed at (1) providing preliminary evidence to the effects of laminar organization of neocortex on the RS-fMRI signal, and (2) evaluating the application of laminar maps to aid the classification of IC maps. We created laminar maps 1–4 that depict relative cortical thickness of layers IV and VI. Our data show that the RS-fMRI signal is significantly related to the relative thickness of the cortical layer VI but not layer IV. Importantly, the laminar maps 1–4 overlap with four separate IC maps. Thus, the laminar maps 1–4 improve classification and interpretation of the IC maps. Moreover, the laminar maps 1–4 may be considered as FC networks that are the bridging piece between particular cognitive functions. Together, these data provide preliminary evidence to the fundamental questions about the role of cortical layering in the RS-fMRI signal and brain FC networks.

Computational fluid dynamics of internal mammary artery-left anterior descending artery anastomoses.

The aim of this study was to elucidate the remodelling of the internal mammary artery (IMA)-left anterior descending artery anastomosis and compare 2 different anastomosis techniques (end-to-side versus side-to-side) using computational fluid dynamics. This study included 9 patients. Computed tomography (CT) angiography was performed immediately after coronary artery bypass grafting (CABG) and at 3-6 months later. The computational fluid dynamics models were made using the CT data. The pulsatile 3-dimensional blood flow was achieved with the finite volume method to evaluate the postoperative morphological and haemodynamic changes at the anastomosis in each patient. Flow velocity distribution, wall shear stress (WSS) and its fluctuation oscillatory shear index were measured. No early or mid-term graft occlusion was observed in the study series. In the side-to-side anastomosis, pouch formation at the distal end of IMA caused a vortex flow with low WSS immediately after CABG. However, at 3-6 months after surgery, this pouch disappeared. As a result, the laminar straight flow with uniform WSS distribution was achieved inside the anastomosis. In the end-to-side anastomosis, the anastomosis shape was remodelled, resulting in a laminar flow pattern with uniform WSS distribution. A patchy high oscillatory shear index was detected at the IMA wall on the top of anastomosis in either anastomosis techniques immediately after the surgery, but it disappeared at 3-6 months after surgery. Regardless of the anastomosis technique used, a successful remodelling of the IMA-left anterior descending artery anastomosis shape was achieved a few months after surgery, resulting in a straightforward flow streamline, with uniform WSS distribution and minimal oscillatory shear index.

Systematic modelling of the development of laminar projection origins in the cerebral cortex: Interactions of spatio-temporal patterns of neurogenesis and cellular heterogeneity.

The architectonic type principle conceptualizes structural connections between brain areas in terms of the relative architectonic differentiation of connected areas. It has previously been shown that spatio-temporal interactions between the time and place of neurogenesis could underlie multiple features of empirical mammalian connectomes, such as projection existence and the distribution of projection strengths. However, so far no mechanistic explanation for the emergence of typically observed laminar patterns of projection origins and terminations has been tested. Here, we expand an in silico model of the developing cortical sheet to explore which factors could potentially constrain the development of laminar projection patterns. We show that manipulations which rely solely on spatio-temporal interactions, namely the relative density of laminar compartments, a delay in the neurogenesis of infragranular layers relative to layer 1, and a delay in the neurogenesis of supragranular layers relative to infragranular layers, do not result in the striking correlation between supragranular contribution to projections and the relative differentiation of areas that is typically observed in the mammalian cortex. In contrast, we find that if we introduce systematic variation in cell-intrinsic properties, coupling them with architectonic differentiation, the resulting laminar projection patterns closely mirror the empirically observed patterns. We also find that the spatio-temporal interactions posited to occur during neurogenesis are necessary for the formation of the characteristic laminar patterns. Hence, our results indicate that the specification of the laminar patterns of projection origins may result from systematic variation in a number of cell-intrinsic properties, superimposed on the previously identified spatio-temporal interactions which are sufficient for the emergence of the architectonic type principle on the level of inter-areal connectivity in silico.

Modelling and Analysis Library Development for Helicopter Blade and Slender Wings

In this study, we suggest a framework for optimal design of a composite wing structure with a high aspect ratio at the initial design stage. The optimization framework calculates allowances in the first ply failure, buckling failure and bearing-bypass failure, which are frequent failure modes in the wing structure, using the laminate pattern database built up through past design experiences, and optimizes the weight of the wing structure within the range of the economic minimal safety margin. In order to verify the optimization framework, finite element analysis for the wing structure of an unmanned air vehicle was configured. Subsequently, static analysis and stability analysis were performed to verify robustness and reliability of the optimization framework by entering the composite material laminate data created from the optimization framework into the finite element model of the wing of an unmanned air vehicle. The optimization framework suggested in this study is an automated algorithm that can carry out sizing of various shapes composed of composite material from the concept design stage, and thus reduce the revised and repeated design time.

Doppler characteristics of hepatic venous hemodynamics in adult healthy camels (Camelus dromedarius)

Abstract The present study was designed to describe the Doppler measurements of hepatic venous blood flow in camels (Camelus dromedarius). A total number of 9 adult healthy camels underwent hepatic Doppler examinations on the right side between the 11th and 9th intercostal spaces. The splenic and cranial mesenteric veins showed turbulent blood flows at their fusion to form the main portal trunk. At porta hepatis, the main portal vein exhibited turbulent blood flows and the mean velocities ranged from 21 to 28 cm/sec. In contrast, the intrahepatic branches of portal veins revealed smooth laminar spectral patterns with low blood velocities ranged from 12 to 22 cm/sec. In addition, hepatic veins and caudal vena cava have laminar blood flows. In conclusion, as a non-invasive clinical tool, Doppler ultrasonography is a simple and easy applicable method for assessment of hepatic hemodynamics in camels (Camelus dromedaries). The present findings have the potential to serve as references for evaluating the health status of the liver from camels. Therefore; a further research study, including comparative evaluation of Doppler findings in camels with various hepatic diseases, may be required.

Effects of temperature and fluid velocity on beer pasteurization in open and closed loop heating systems: numerical modeling and simulation

Abstract A two-dimensional symmetric heat transfer model and a fluid rotation model were established to study beer pasteurization process through the COMSOL Multiphysics software. Two heating modes, including closed-loop heating (CLH) and open-loop heating (OLH), were considered. There was a significant natural convection phenomenon in both heating systems. However, the natural convection became weaker with a gradual increase in the heating temperature of the beer. The maximum fluid velocity (FV) in CLH and OLH modes was 69.34 and 43.74 mm/s, respectively. After heating at 333.13 K for 20 min, the minimum and maximum pasteurization unit (PU) values in CLH were 55 and 59, respectively, while the corresponding values for OLH were 30 and 55, respectively. The pasteurization effect under the CLH mode was better than the OLH one. The heat transfer was also affected by fluid flow (laminar and turbulence) patterns. The PU value was nonlinearly related to the FV. The optimal FV can be obtained at ∼50 mm/s.

Distinct Laminar and Regional Patterns of GABA Neuron Subtypes in Monkey Prefrontal and Visual Cortices: An RNAscope Analysis

Distinct Laminar and Regional Patterns of GABA Neuron Subtypes in Monkey Prefrontal and Visual Cortices: An RNAscope Analysis

Changes in Wnt-Dependent Neuronal Morphology Underlie the Anatomical Diversification of Neocortical Homologs in Amniotes

The six-layered neocortex is a shared characteristic of all mammals, but not of non-mammalian species, and its formation requires an inside-out pattern of neuronal migration. The extant reptilian dorsal cortex is thought to represent an ancestral form of the neocortex, although how the reptilian three-layered cortex is formed is poorly understood. Here, we show unique patterns of lamination and neuronal migration in the developing reptilian cortex. While the multipolar-to-bipolar transition of migrating neurons is essential for mammalian cortical development, the reptilian cortex lacks bipolar-shaped migrating neurons, resulting in an outside-in pattern of cortical development. Furthermore, dynamic regulation of Wnt signal strengths contributes to neuronal morphological changes, which is conserved across species. Our data preclude the idea that the six-layered mammalian neocortex emerged by simple addition to the reptilian dorsal cortex but suggest that the acquisition of a novel neuronal morphology based on conserved developmental programs contributed to neocortical evolution.

Fish Species Identification Using the Rhombic Squamation Pattern

The shape of fish scales is to a considerable degree species-specific, making it possible to identify species using only one scale per specimen. However, the shape of the rhombic lamination pattern has not been considered to identify species. This study used geometric morphometric statistical approaches to address two specific questions: (1) whether the rhombic lamination pattern of fish scales along the longitudinal axis varies within species and sex and (2) how many fish scales of the rhombic squamation pattern should be considered to obtain an adequate identification. These questions were assessed with Mancova and cross-validated quadratic discriminant analysis (DA) using the rhombus of one, three and six scales, and six, 14 and 26 landmarks, respectively, in order to discriminate between two co-generic species, Mugil cephalus and M. curema. The proportions of the total shape variance explained by the total length and the centroid size were 2.3, 11.8 and 10.5% and 4.2, 5.1 and 5.4% for 1, 3 and 6 scales, respectively. Analyses were carried out on the shape and the form (shape plus size). The Mancova and DA analyses were found to be effective in detecting differences in scale pattern shape between species (except in the case of 3 scales; p=0.079 for the shape and p=0.065 for the form), whereas no differences were recorded between size and sex in all cases. The findings indicate that a good identification of species is possible, with no significant differences when using shape or form. The discriminant analyses provided values of 75.8, 75.0 and 73.4% based on the shape, and of 72.7, 75.8 and 75.0% based on the form, for 1, 3 and 6 scales respectively. Thus, it is possible to obtain a rapid and reliable identification of species using the rhombus of one scale only without considering the size. This is a useful finding in practical terms since scaling requires data on length. In addition, the finding of a suitable discrimination using only the rhombus of one scale raises the possibility of using an ocular adaptor on a camera or mobile, allowing many individuals to be easily screened without having to collect scales.