Effect of partial substitution of fishmeal with insect meal (Hermetia illucens) on gut neuromuscular function in Gilthead sea bream (Sparus aurata).

Alternative nutrient sources to fishmeal for fish feed, such as insect meals, represent a promising sustainable supply. However, the consequences for fish digestive function have not been exhaustively investigated. In the present study we evaluated the effect of partial fishmeal substitution with 10% Hermetia illucens (Hi10) larvae meal on the neuromuscular function of proximal and distal intestine in gilthead sea bream. In animals fed with insect meal, weight and growth parameters were similar to controls fed with conventional fishmeal. In addition, no anomalies in intestinal gross morphology and no overt signs of inflammation were observed. The gastrointestinal transit was significantly reduced in Hi10 fed animals. In the proximal and distal intestine longitudinal muscle, Hi10 feeding downregulated the excitatory cholinergic and serotoninergic transmission. Sodium nitroprusside-induced inhibitory relaxations increased in the proximal intestine and decreased in the distal intestine after Hi10 meal. Changes in the excitatory and inhibitory components of peristalsis were associated with adaptive changes in the chemical coding of both proximal and distal intestine myenteric plexus. However, these neuromuscular function alterations were not associated with considerable variations in morphometric growth parameters, suggesting that 10% Hi meal may represent a tolerable alternative protein source for gilthead sea bream diets.

Body-shape trajectories and their genetic variance component in Gilthead seabream (Sparus aurata L.).

The phenotype of juvenile fish is closely associated with the adult phenotype, thus consisting an important quality trait for reared fish stocks. In this study, we estimated the correlation between the juvenile and adult body-shape in Gilthead seabream, and examined the genetic basis of the ontogenetic trajectories. The body shape of 959 pit-tagged fish was periodically examined during the juvenile-to-adult period. Individual shape ontogenetic trajectories were studied in respect to the initial (juvenile) and final (adult) phenotypes, as well as to the rate that adult phenotype is attained (phenotypic integration rate). We found that the juvenile body-shape presented a rapid change up to 192.7 ± 1.9 mm standard length, followed by a phenotypically stable period (plateau). Depending on the shape component considered, body-shape correlations between juvenile and adult stages ranged from 0.22 to 0.76. Heritability estimates (h2) of the final phenotype ranged from 0.370 ± 0.077 to 0.511 ± 0.089, whereas h2 for the phenotypic integration rate was 0.173 ± 0.062. To our knowledge, this is the first study demonstrating that the variance of the ontogenetic trajectories has a substantial additive genetic component. Results are discussed in respect to their potential use in selective breeding programs of Gilthead seabream.

Relation of gilthead seabream (Sparus aurata) seasonal reproductive activity to hematology, serum biochemistry, histopathology, and Brdt gene expression.

This study aimed to find the relation of Sparus aurata (gilthead seabream) reproductive activities to some blood parameters as complete blood count, liver enzymes, some hormones related to reproduction process and microscopic findings of gonads, as well as expression of Bromodomain testis-specific gene. Eighty-eight sexually mature seabream were collected and investigated through the four seasons. Red blood cells were higher in autumn and spring. Hemoglobin was high in summer, MCV highest values ​​were seen in winter and summer, while MCHC was highest in summer. The values ​​of white blood cells increased significantly in spring, summer, and autumn compared with winter. The highest value of lymphocytes was recorded in spring and autumn. Eosinophil was recorded the highest value in the spring. The highest value of segmented neutrophils was recorded in summer. The highest value of band neutrophil was recorded in summer and winter. Alanine aminotransferase and aspartate aminotransferase showed high values in the winter. Luteinizing hormone (LH) was higher in females, males, and hermaphrodites during winter. Follicle-stimulating hormone (FSH) was higher in females during spring. The highest value of estradiol 17-ß and progesterone was recorded in summer. The highest value of total testosterone was recorded in spring. Microscopically, ovaries were immature and inactive during spring and summer but well developed in autumn and winter. During spring and summer, testes were immature and began spermatogenesis process but well developed with the appearance of spermatids and spermatozoa during autumn and winter. The expression of Brdt was higher in testes than ovary. Brdt recorded high expression in autumn and spring than in summer and winter.

Differences in otolith shape and fluctuating-asymmetry between reared and wild gilthead seabream (Sparus aurata Linnaeus, 1758).

Otolith structure is a useful tool in discrimination among fish populations as it is a permanent record of the influence of endogenous and exogenous factors. In the present study we examined otolith morphology and fluctuating asymmetry (FA) for differences between wild-caught (by bottom trawl) and reared specimens of Gilthead seabream (Sparus aurata). Based on the frequency of regenerated scales (degree of scale regeneration, SRD) on each specimen, a threshold of 30% SRD was used to assign wild-caught fish individuals as wild (≤30% SRD, LR group) or as possible aquaculture escapees (>30% SRD, HR group). Based on the analysis of elliptic Fourier descriptors, significant differences were found in otolith shape between reared (Rr) and the wild-caught groups (LR, HR). Reared fish had otoliths with significantly larger perimeter (OP ) than wild-caught fish. Furthermore, FA was significantly higher in the Rr than the LR group for OP and all except one shape descriptors (harmonics 2-7). The HR group exhibited intermediate levels of FA between the low and high FA levels observed in the LR and Rr groups. Results are discussed in terms of the value of combining otolith and scale morphology for the identification of escapees in wild Gilthead seabream stocks.

Effects of genetics and early-life mild hypoxia on size variation in farmed gilthead sea bream (Sparus aurata).

The present study evaluated, in an 18-month gilthead sea bream trial, the time course effects of genetics on individual size variation and growth compensation processes in families selected by heritable growth in the PROGENSA® breeding program. Families categorized as fast, intermediate, and slow growing had different growth trajectories with a more continuous growth in fast growth families. This feature was coincident with a reduced size variation at the beginning of the trial that clustered together the half-sib families sharing the same father. Regression analysis evidenced that the magnitude of compensatory growth was proportional to the initial size variation with no rescaling of families at this stage. By contrast, the finishing growth depensation process can mask, at least partially, the previous size convergence. This reflects the different contribution across the production cycle of genetics in growth. How early-life experiences affect growth compensation at juvenile stages was also evaluated in a separate cohort, and intriguingly, a first mild-hypoxia pulse at 60-81 days post-hatching (dph) increased survival rates by 10%, preventing growth impairment when fish were exposed to a second hypoxia episode (112-127 dph). The early hypoxia experience did not have a negative impact on growth compensatory processes at juvenile stages. By contrast, a diminished capacity for growth compensation was found with repeated or late hypoxia experiences. All this reinforces the use of size variation as a main criterion for improving intensive fish farming and selective breeding.

Radiological characterization of gilthead seabream (Sparus aurata) by X-ray computed tomography.

In recent years, the increasing use of fish as new animal models in scientific research and the growth of fish farming (mainly for human consumption) have highlighted the need for advanced technology to deepen our knowledge of fish biology. Hence, the present study was carried out to radiologically analyse the whole body of gilthead seabream (Sparus aurata) specimens using X-ray computed tomography (CT). Images were acquired in an Albira SPECT/PET/CT tri-modal preclinical-scanner. Segmentation, measurements and three-dimensional reconstruction were made using the Carestream Molecular imaging Albira CT system in conjunction with Pmod, AMIDE and Amira software packages. The results showed that the density values of gilthead seabream are in the range -700 to +2500 HU for the whole body. We also determined the density ranges that topographically coincide with the swim bladder, soft tissues, fat, skin and skeleton. This work describes, validates and demonstrates the application of a fully automated image analysis technique to study and quantify fish body composition, whether segmented or as a whole. In addition, the basis for applying this image technique in other in vivo studies is established.

A tomographic study of the histological structure of teeth in the gilthead sea bream, Sparus aurata (Teleostei, Perciformes, Sparidae).

X-ray tomography shows that caniniform and molariform teeth of the gilthead sea bream, Sparus aurata, have a simplexodont plicidentine organization. Together with an insertion of the teeth in alveolae, and the presence of bony shafts sustaining the dental plate, the simplexodont plicidentine is linked to the durophagous diet of the fish.

Early development and occurrence patterns of the Pagrinae seabream Argyrops bleekeri (Perciformes: Sparidae): Does early life history have implications for sparid relationships?

The early development and occurrence patterns of Argyrops bleekeri are described based on 87 specimens collected from Nakagusuku Bay on Okinawa Island in southwestern Japan. Larvae and juveniles of the genus Argyrops are distinguished from the other seabreams inhabiting the Western Pacific region by the strength and extent of head spination, body depth, dorsal-fin-ray counts and melanophore patterns. Argyrops bleekeri is easily distinguished from other members of this genus by the presence of a single rudimentary dorsal-fin spine on the first dorsal pterygiophore, melanophore patterns and an allopatric distribution. Argyrops bleekeri larvae [3.3-7.1 mm body length (BL)] and juveniles (6.7-13.0 mm BL) were found in the bay from January to May; nonetheless, they were not collected from the outer bay or in extremely shallow inshore areas such as tidal flats. The results suggest that Argyrops is the most derived red seabream because of its spiny morphology, and it may be a member of an expanding nearshore group of red seabreams, which originally inhabited offshore waters.

Morphological and histological characterization of an ectopically mineralized structure in a gilthead sea bream Sparus aurata with opercular deformation.

In this study, we describe an abnormal ectopically mineralized structure (EMS) that was found inside the skull of a juvenile Sparus aurata that also showed a bilateral opercular deformation. The overall phenotype and tissue composition were studied using micro-CT scanning and histological analyses. The ectopic structure occupies a large volume of the brain cavity, partially extruding into the gill cavity. It shows a dense mineralization and an extracellular matrix-rich phenotype, with variation in both the morphology and size of the cell lacunae, combined with an irregular fibre organization inside the matrix. This study is the first to report such an EMS in a juvenile teleost fish, where the tissue does not resemble any other connective tissue type described in bony fish so far. The tissue phenotype seems to rule out that the EMS corresponds to a tumorous cartilage. Yet, it is rather reminiscent of a highly mineralized structure found in cartilaginous fish, where it is suggested to be associated with damage repair.

Age and growth of black seabream Acanthopagrus schlegelii(Sparidae) in Hong Kong and adjacent waters of the northern South China Sea.

Age and growth of the black seabream Acanthopagrus schlegelii (family Sparidae) from the northern South China Sea (NSCS) were studied by reading growth rings in sectioned sagittal otoliths. Ring formation frequency was determined to be annual by using marginal increment analysis. The von Bertalanffy growth function parameters were estimated as: L∞ = 43.7 cm LS ; K =0.22 year; t0 = -1.59 years. Functional males are significantly younger than functional females, with sexually transitional individuals between the modal ages of males and females supporting protandry in this species. Males become sexually mature within 1 year and 50% age at sex change is at 2 years. The maximum age recorded for both males and females sampled was 9 years which is lower than for conspecifics elsewhere and may reflect high fishing pressure in the study area when compared with conspecifics in other areas or could reflect latitudinal effects. Otolith mass was significantly and positively related to age, providing a cheap and quick alternative method for approximating age. Acanthopagrus schlegelii is a relatively fast-growing and rapidly maturing species attaining a similar asymptotic length to conspecifics. A need for fishery management is indicated to protect both young juveniles and older adults, especially females, to increase reproductive output and safeguard fishery production.

Neurochemical characterization of myenteric neurons in the juvenile gilthead sea bream (Sparus aurata) intestine.

We evaluated the chemical coding of the myenteric plexus in the proximal and distal intestine of gilthead sea bream (Sparus aurata), which represents one of the most farmed fish in the Mediterranean area. The presence of nitric oxide (NO), acetylcholine (ACh), serotonin (5-HT), calcitonin-gene-related peptide (CGRP), substance P (SP) and vasoactive intestinal peptide (VIP) containing neurons, was investigated in intestinal whole mount preparations of the longitudinal muscle with attached the myenteric plexus (LMMP) by means of immunohistochemical fluorescence staining. The main excitatory and inhibitory neurochemicals identified in intestinal smooth muscle were ACh, SP, 5HT, and NO, VIP, CGRP. Some neurons displayed morphological features of ascending and descending interneurons and of putative sensory neurons. The expression of these pathways in the two intestinal regions is largely superimposable, although some differences emerged, which may be relevant to the morphological properties of each region. The most important variances are the higher neuronal density and soma size in the proximal intestine, which may depend on the volume of the target tissue. Since in the fish gut the submucosal plexus is less developed, myenteric neurons substantially innervate also the submucosal and epithelial layers, which display a major thickness and surface in the proximal intestine. In addition, myenteric neurons containing ACh and SP, which mainly represent excitatory motor neurons and interneurons innervating the smooth muscle were more numerous in the distal intestine, possibly to sustain motility in the thicker smooth muscle coat. Overall, this study expands our knowledge of the intrinsic innervation that regulates intestinal secretion, absorption and motility in gilthead sea bream and provides useful background information for rational design of functional feeds aimed at improving fish gut health.

Using an integral projection model to assess the effect of temperature on the growth of gilthead seabream Sparus aurata.

Accurate information on the growth rates of fish is crucial for fisheries stock assessment and management. Empirical life history parameters (von Bertalanffy growth) are widely fitted to cross-sectional size-at-age data sampled from fish populations. This method often assumes that environmental factors affecting growth remain constant over time. The current study utilized longitudinal life history information contained in otoliths from 412 juveniles and adults of gilthead seabream, Sparus aurata, a commercially important species fished and farmed throughout the Mediterranean. Historical annual growth rates over 11 consecutive years (2002-2012) in the Gulf of Lions (NW Mediterranean) were reconstructed to investigate the effect of temperature variations on the annual growth of this fish. S. aurata growth was modelled linearly as the relationship between otolith size at year t against otolith size at the previous year t-1. The effect of temperature on growth was modelled with linear mixed effects models and a simplified linear model to be implemented in a cohort Integral Projection Model (cIPM). The cIPM was used to project S. aurata growth, year to year, under different temperature scenarios. Our results determined current increasing summer temperatures to have a negative effect on S. aurata annual growth in the Gulf of Lions. They suggest that global warming already has and will further have a significant impact on S. aurata size-at-age, with important implications for age-structured stock assessments and reference points used in fisheries.

Long term exposure to cadmium: Pathological effects on kidney tubules cells in Sparus aurata juveniles.

The effects of an exposure to cadmium chloride 0.47µM for 150days were studied in kidneys of juveniles Sparus aurata by a multidisciplinary approach so to correlate uptake and detoxification potential to changes in brush border and glycocalyx sugar composition. Results demonstrated that cadmium concentration in kidney significantly increased from day 30 reaching a plateau on day 120 while metallothioneins reached a peak on day 90 and by day 120 were already decreasing to control values. Cytological damage was extensive on day 90, clearly detectable at both structural and ultrastructural levels, in tubular cells and brush-border. Staining with a panel of four lectins revealed a significant increase in N-Ac-Gal and a decrease in mannose in the glycocalyx and the tubular basal membranes. From day 120, when cadmium concentration was high and metallothionein concentration decreasing, a clear recovery was observed in tubular cells morphology and sugar composition. Possible significance of these apparently contrasting data are discussed.

Visual adaptations of the eye of the gilthead sea bream (Sparus aurata).

The current investigation represents the morphological description of the adaptation of gilthead sea bream Sparus aurata to its environmental conditions. For the achievement of this study twelve mature fishes were used for gross, light and electron microscope examinations. The cornea is consists of three layers; an anterior stratified cuboidal epithelium, bowman layer, and a dermal stroma. A mucoid layer located between the dermal stroma and the anterior part of the scleral cornea, while the iridescent layer located between the anterior and the posterior scleral stroma. The retina is composed of ten layers. There are two areas of the retina; non-nervous and nervous. The non-nervous area is represented only by the thick pigmented epithelium layer. The retina has both rod and cone photoreceptors. The cones are differentiated into three types; single, double and triple cones. Rods inner segments contain numerous mitochondria while that of the cones has ellipsosomes. These ellipsosomes may function in condensing light in the outer segment. There is a clear correlation between ellipsosomes formation in the inner segment of cone and night condition.

Dorso-ventral skin characterization of the farmed fish gilthead seabream (Sparus aurata).

The skin is the first barrier of defence in fish, protecting against any external stressor and preserving the integrity and homeostasis of the fish body. The aim of this study was to characterise gilthead seabream skin by isolating cells and studying the cell cycle by flow cytometry, to study the skin histology by scanning electron microscopy and the transcription level of some immune-relevant genes by RT-PCR. Furthermore, the results obtained from samples taken from the dorsal and the ventral part of the specimens are compared. No differences were observed in the cell cycle of cells isolated from the dorsal and ventral zones of the skin or in the gene expression of the genes studied in both epidermal zones. However, the epidermis thickness of the ventral skin was higher than that of the dorsal skin, as demonstrated by image analysis using light microscopy. Besides, scanning electron microscopy pointed to a greater cell size and area of microridges in the apical part of the dorsal epidermal cells compared with ventral skin epidermal cells. This study represents a step forward in our knowledge of the skin structure of an important farmed teleost, gilthead seabream, one of the most commonly farmed fish worldwide. Furthermore, for functional characterization, experimental wounds were carried out comparing the wound healing rate between the dorsal and ventral regions of skin over the time. The results showed higher ratio of wound healing in the ventral region, whose wounds were closed after 15 days, compared to dorsal region of skin. Taking into account all together, this study represents a step forward in our knowledge of the skin structure and skin regeneration of an important farmed teleost, gilthead seabream, one of the most commonly farmed fish worldwide.

The Tongue Dorsal Surface in Fish: A Comparison Among Three Farmed Species.

The oral cavity of vertebrates has a very important role in many functions strictly related to the food processing. Two species, sea bass Dicentrarchus labrax and seabream Sparus aurata, are mainly involved in the aquaculture industry in the mediterranean area; moreover, the white seabream Diplodus sargus sargus was recently chosen as the best candidate for the diversification of species of commercial interest. This investigation was carried out, using the standard procedures for light and scanning electron microscopy, to analyse the morphology of the tongue dorsal surface in order to show whether relationships are present between the tongue morphology and the nutritional choices of these species. In all the three investigated species, three different areas were observed on the dorsal lingual surface: an apex, a body and a root. In the sea bass D. labrax, numerous caninelike teeth, organized in pads, were present along the dorsal surface. The presence of numerous taste buds, scattered on the tongue, was shown. In the seabream S. aurata, the apical part of the tongue is inserted in a pouch with a characteristic medial ridge on the body surface. Numerous taste buds were scattered on the whole surface. In the white seabream D. sargus sargus, a pouch partially covering the apex was clearly observed. In the pouch, filiform-like and foliate-like papillae can be distinguished. The results show the important role of the fish tongue in the food ingestion process, demonstrating the interaction of food processing, taste and morphological characteristics.

Unveiling the neurotoxicity of methylmercury in fish (Diplodus sargus) through a regional morphometric analysis of brain and swimming behavior assessment.

The current study aims to shed light on the neurotoxicity of MeHg in fish (white seabream - Diplodus sargus) by the combined assessment of: (i) MeHg toxicokinetics in the brain, (ii) brain morphometry (volume and number of neurons plus glial cells in specific brain regions) and (iii) fish swimming behavior (endpoints associated with the motor performance and the fear/anxiety-like status). Fish were surveyed for all the components after 7 (E7) and 14 (E14) days of dietary exposure to MeHg (8.7µgg-1), as well as after a post-exposure period of 28days (PE28). MeHg was accumulated in the brain of D. sargus after a short time (E7) and reached a maximum at the end of the exposure period (E14), suggesting an efficient transport of this toxicant into fish brain. Divalent inorganic Hg was also detected in fish brain along the experiment (indicating demethylation reactions), although levels were 100-200 times lower than MeHg, which pinpoints the organic counterpart as the great liable for the recorded effects. In this regard, a decreased number of cells in medial pallium and optic tectum, as well as an increased hypothalamic volume, occurred at E7. Such morphometric alterations were followed by an impairment of fish motor condition as evidenced by a decrease in the total swimming time, while the fear/anxiety-like status was not altered. Moreover, at E14 fish swam a greater distance, although no morphometric alterations were found in any of the brain areas, probably due to compensatory mechanisms. Additionally, although MeHg decreased almost two-fold in the brain during post-exposure, the levels were still high and led to a loss of cells in the optic tectum at PE28. This is an interesting result that highlights the optic tectum as particularly vulnerable to MeHg exposure in fish. Despite the morphometric alterations reported in the optic tectum at PE28, no significant changes were found in fish behavior. Globally, the effects of MeHg followed a multiphasic profile, where homeostatic mechanisms prevented circumstantially morphometric alterations in the brain and behavioral shifts. Although it has become clear the complexity of matching brain morphometric changes and behavioral shifts, motor-related alterations induced by MeHg seem to depend on a combination of disruptions in different brain regions.

Sagittal otolith morphology of sharpsnout seabream Diplodus puntazzo (Walbaum, 1792) in the Aegean Sea / Morfología de los otolitos sagitales del sargo picudo Diplodus puntazzo (Walbaum, 1792) en el Mar Egeo

The morphology, biometry and shape indices of the left and right sagittal otoliths were studied for sharpsnout seabream, Diplodus puntazzo species from Aegean Sea. The shape, sulcus acusticus shape, proximal and distal surfaces, anterior and posterior regions of left and right sagittal otoliths for a total of 52 D. puntazzo were analyzed. The morphometric measurements such as weight, length, width, area and perimeter were recorded for each pair of sagittal otoliths of the sharpsnout seabream. The shape indices such as form factor, roundness, aspect ratio, circularity, rectangularity, and ellipticity were calculated for left and right sagittal otoliths of D. puntazzo. The otolith width and ellipticity were significantly different (P <0.05) for left and right sagittal otolith measurements and shape indices, respectively in D. puntazzo inhabiting the Aegean Sea. Morphological characteristics of fish otoliths were highly variable in species and populations; there was limited information on the sagittal otolith morphology and shape indices. The present study provided sufficient information of the sharpsnout seabream left and right otolith morphologies, biometry, and shape indices in the Aegean Sea, they may provide a useful tool for marine and freshwater species discrimination and identification in further investigations.

Los índices morfológicos, biometría y la forma de los otolitos sagitales izquierdo y derecho se estudiaron para la especie sargo picudo, Diplodus puntazzo del mar Egeo. Se analizaron en 52 D. puntazzo la forma del surco acústico, las superficies proximal y distal y las regiones posteriores de los otolitos sagitales izquierdo y derecho. Además, se registraron para cada par de otolitos sagitales las mediciones morfométricas de peso, longitud, ancho y perímetro. Se calcularon en ambos otolitos sagitales los índices de forma, factor de forma, relación de aspecto, circularidad, ortogonalidad y elipticidad. En el D. puntazzo que habita en el mar Egeo, el ancho y elipticidad de los otolitos fueron significativamente diferentes (P <0,05), para las mediciones de otolitos sagitales izquierdo y derecho, respectivamente. Existen gran variabilidad en las características morfológicas de los otolitos de diferentes especies y poblaciones de peces, asimismo es limitada la información de los índices morfológicos y la forma de los otolitos sagitales. El presente estudio proporciono información suficiente sobre la morfología y biometría de los otolitos izquierdo y derecho del sargo picudo en el Mar Egeo, lo que puede proporcionar una herramienta útil para la discriminación e identificación de especies marinas de agua dulce y para nuevas investigaciones.

Morphological characterization of the oral cavity of the gilthead seabream (Sparus aurata) with emphasis on the teeth-age adaptation.

Gilthead sea bream with different age groups that collected from Seawater fisheries, Ismailia Governorate, Egypt, were examined by gross anatomy and scanning electron microscopy to assess the morphological characteristics of the oral cavity. Teeth patterns showed that the gilthead sea bream is adapted to the feeding pattern according to age development, as it modified from spiny form teeth in young fishes to obelisk-like teeth and flat dome-like teeth in growing fishes, with differentiation of teeth into three pairs of canine and conical teeth, that later differentiated to small and large flat teeth. With development, the apical pouch also showed morphological differentiation from curve-like in small fishes to Y-letter shape in medium-sized fishes, which later grow to completely covering the lower jaw in grown adult fishes. Tongue papillae, on the other hand, showed some differentiation being smoother in growing fishes than adult ones. Consistent with development differentiation, the palatine region of young fishes appeared separated from the palate by deep palatine fissure, while that the same palatine region was continuous with the palate with a remnant of palatine fissure as shallow groove was noticed in grown big fishes. Taste buds were characterized in the oral cavity of small and large fishes however in large fishes; the taste buds were more prominent especially at the palate and palatine folds. These and other morphological features of the oral cavity and the feeding habits in small and large gilthead sea bream fishes were recorded.

Vertebrae length and ultra-structure measurements of collagen fibrils and mineral content in the vertebrae of lordotic gilthead seabreams (Sparus aurata).

Skeletal deformities of gilthead seabream (Sparus aurata) are a major factor affecting the production cost, the external morphology and survival and growth of the fish. Adult individuals of S. aurata were collected from a commercial fish farm in Greece and were divided into two groups: one with the presence of lordosis, a skeletal deformity, and one without any skeletal deformity. Fishes were X-rayed, and cervical, abdominal and caudal vertebrae lengths were measured. Vertebrae were taken from the site of the vertebral column where lordosis occurred. One part was decalcified and prepared for collagen examination with transmission electron microscopy, and the rest were incinerated, and the Ca and P contents were measured. The stoichiometries of the samples were obtained by EDS (Energy Dispersive Spectroscopy). The same procedure was followed for fish without skeletal deformities (vertebrae were taken from the middle region of the vertebral column). The decalcified vertebrae parts were examined with TEM, collagen micrographs were taken and the fibrils' periods and diameters were measured. There were no significant differences for both Ca and P or the collagen fibrils' periods between the two fish groups. The mean lengths of the cervical, abdominal and caudal vertebrae where lordosis occurred were similar to the lengths of the respective regions of the individuals without the skeletal deformity. The TEM examination showed a significantly smaller mean vertebrae collagen fibril diameter from the fishes with lordosis compared with those from the controls, revealing the significance of collagen to bone structure.