Asymmetry of Sagittal Otolith Shape Based on Inner Ear Side Tested on Mediterranean Red Mullet (Mullus barbatus Linnaeus, 1758): Comparative Analysis of 2D and 3D Otolith Shape Data

Sagittal otolith shape analysis is one of the most widespread techniques worldwide to discriminate fish stock units, as this proxy integrates both environmental and genetic factors. All previous otolith shape studies have been carried out using two-dimensional (2D) images, a partial representation of the whole shape of the otolith. However, prior to the identification of stock unit boundaries, the influence of other potential drivers controlling the otolith shape must be analysed to limit their bias. In this study, the presence of asymmetry in otolith shape depending on the inner ear side (i.e., left versus right inner ears) was tested by comparing the approaches of 2D and three-dimensional (3D) sagittal otolith shape analyses. Eighty-two red mullet adults (Mullus barbatus) from three locations in the eastern part of the Mediterranean Sea were studied. Fourier harmonic descriptors computed from 2D outlines and spherical harmonic descriptors computed from 3D meshes were used to evaluate otolith shape variation. The results of a multivariate mixed-effects model from 2D images showed that there was no asymmetry effect of inner ear side on the otolith shape in any location. There was, however, a significant geographical effect for the 2D otolith shape between the Adriatic Sea and the Levantine Sea. In contrast, 3D information showed that both side effects and geographical differences were significant. This is the first study comparing 2D and 3D data showing different results on the same sample of red mullet. These results demonstrate the importance of 3D otolith shape analysis for stock discrimination

Potential directional asymmetry of the otolith shape tested on the red mullet (Mullus barbatus) in the Mediterranean Sea: comparative analysis of 2D and 3D otolith shape data

A wide number of techniques were developed and applied to identify and discriminate stocks. Among them, otolith’s shape, which is affected by environment and genetic factors, can be used as a tool to identify the populations within the species. Before to identify the boundaries of stocks, the potential drivers, which control the otolith shape, must be analysed. In this study, Directional Asymmetry (DA; the effect of otolith’s location side, i.e., left versus right inner ear) was tested combining the approaches to otolith shape in 2D and 3D on 560 adults of the red mullet Mullus barbatus (Linnaeus, 1758) which is one of the most abundant demersal fish species in the Mediterranean Sea. Studied individual were sampled from 7 subunits for 2D analysis (476 individuals) and 3 subunits for 3D analysis (84 individuals) of geographical subareas (GSAs). To analyse otolith shape, the normalized Elliptical Fourier Descriptors (EFDs) computed from the two-dimensional outlines (extracted from otolithes 2D pictures) and Spherical Harmonic shape descriptors computed from three-dimensional surfaces/meshes (extracted from otolithes 3D scans) were analysed with principal component analysis (PCA) method. PCA’s scores were used in the multivariate mixed-effects model with side and subunits effects. From 3D surfaces/meshes, the univariate variables (i.e. otolithe’s surface and volume) were analysed with Redundancy analysis (RDA) too. The EFDs from 2D images showed that the side effect was significant on the otolith shape (p-value<0.00001). The reconstructed outlines of the mean Fourier harmonics of the left and right side were plotted and the percentage of non-overlapping surface was 1.010%. However, the interaction between side and geographical subareawas  nosignificant from 2D images. The EFDs from 3D images showed that the side effect was signifant (p-value<0.00001). In additionnal, the interaction between side effect and geographical subarea was signifiant (p-value< 0.00001) from 3D images. The relationship between the fish length and the surface of 3D otolith shape was significant (p-value =0.001), this trend was not observed by the otolith volume (p-value=0.698). For these two univariate descriptors of 3D otolith shape, there were no significant difference between left and right otoliths. This comparative analysis of otolith shape in 2D and in 3D showed showed that the 3D approach, presents the data with more accuracy than those extracted from the regurlarly used 2D approach. This difference is very important because the directionnal asymmetry was significant on the relationship between the otolith 3D shape and the geographical area of sampling while this trend is not observable from the otolith 2D shape.  This first study showing the difference between 2D and 3D approaches should be confirmed in the future

Asymmetry of Sagittal Otolith Shape Based on Inner Ear Side Tested on Mediterranean Red Mullet (Mullus barbatus Linnaeus, 1758): Comparative Analysis of 2D and 3D Otolith Shape Data

International audienceSagittal otolith shape analysis is one of the most widespread techniques worldwide to discriminate fish stock units, as this proxy integrates both environmental and genetic factors. All previous otolith shape studies have been carried out using two-dimensional (2D) images, a partial representation of the whole shape of the otolith. However, prior to the identification of stock unit boundaries, the influence of other potential drivers controlling the otolith shape must be analysed to limit their bias. In this study, the presence of asymmetry in otolith shape depending on the inner ear side (i.e., left versus right inner ears) was tested by comparing the approaches of 2D and three-dimensional (3D) sagittal otolith shape analyses. Eighty-two red mullet adults (Mullus barbatus) from three locations in the eastern part of the Mediterranean Sea were studied. Fourier harmonic descriptors computed from 2D outlines and spherical harmonic descriptors computed from 3D meshes were used to evaluate otolith shape variation. The results of a multivariate mixed-effects model from 2D images showed that there was no asymmetry effect of inner ear side on the otolith shape in any location. There was, however, a significant geographical effect for the 2D otolith shape between the Adriatic Sea and the Levantine Sea. In contrast, 3D information showed that both side effects and geographical differences were significant. This is the first study comparing 2D and 3D data showing different results on the same sample of red mullet. These results demonstrate the importance of 3D otolith shape analysis for stock discrimination

Analyse de forme en 3D des otolithes pour mieux délimiter les stocks du rouget barbet de vase en utilisant l'asymétrie des côtés de l'oreille interne

L’otolithe est une structure calcifiée présente dans l’oreille interne des poissons. L'analyse de la forme de l'otolithe est l'une des techniques les plus répandues dans le monde pour distinguer les unités de stock de poissons, car elle intègre à la fois des facteurs environnementaux et génétiques. Toutes les études précédentes sur la forme de l'otolithe ont été réalisées à l'aide d'images bidimensionnelles (2D), une représentation partielle de la forme totale de l'otolithe. Avant d'identifier les limites des unités de stock, l'influence d'autres facteurs potentiels contrôlant la forme de l'otolithe doit être analysée afin de limiter leur biais. Dans cette étude, la présence d'une asymétrie dans la forme de l'otolithe en fonction du côté de l'oreille interne (c'est-à-dire l'oreille interne gauche par rapport à l'oreille interne droite) a été testée sur le rouget barbet de vase (Mullus barbartus) provenant de la mer Méditerranée ; en comparant les approches des analyses de la forme de l'otolithe en 2D et en trois dimensions (3D). Les résultats montrent que les images 3D peuvent détecter des différences significatives là où les images 2D ne les détecte pas

Organic Matrices of Calcium Carbonate Biominerals Improve Osteoblastic Mineralization

International audienceMany organisms incorporate inorganic solids into their tissues to improve functional and mechanical properties. The resulting mineralized tissues are called biominerals. Several studies have shown that nacreous biominerals induce osteoblastic extracellular mineralization. Among them, Pinctada margaritifera is well known for the ability of its organic matrix to stimulate bone cells. In this context, we aimed to study the effects of shell extracts from three other Pinctada species (Pinctada radiata, Pinctada maxima, and Pinctada fucata) on osteoblastic extracellular matrix mineralization, by using an in vitro model of mouse osteoblastic precursor cells (MC3T3-E1). For a better understanding of the Pinctada-bone mineralization relationship, we evaluated the effects of 4 other nacreous mollusks that are phylogenetically distant and distinct from the Pinctada genus. In addition, we tested 12 non-nacreous mollusks and one extra-group. Biomineral shell powders were prepared, and their organic matrix was partially extracted using ethanol. Firstly, the effect of these powders and extracts was assessed on the viability of MC3T3-E1. Our results indicated that neither the powder nor the ethanol-soluble matrix (ESM) affected cell viability at low concentrations. Then, we evaluated osteoblastic mineralization using Alizarin Red staining and we found a prominent MC3T3-E1 mineralization mainly induced by nacreous biominerals, especially those belonging to the Pinctada genus. However, few non-nacreous biominerals were also able to stimulate the extracellular mineralization. Overall, our findings validate the remarkable ability of CaCO3 biomineral extracts to promote bone mineralization. Nevertheless, further in vitro and in vivo studies are needed to uncover the mechanisms of action of biominerals in bone