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Restocking initiatives have the potential to help conserve populations of threatened species, and there is a growing interest in applying this approach to marine fish. Sciaena umbra and Dentex dentex are two coastal fish species that inhabit the Mediterranean Sea and are categorized as 'Vulnerable' according to the IUCN Red List. This study investigated the performance of S. umbra and D. dentex hatchery-reared juveniles feeding on live prey. We evaluated whether 6 days of training and body size had an impact on feeding performance and behaviour. In both species, we found that training had a positive effect on fish feeding performance by (1) significantly increasing mean number of prey eaten, (2) decreasing the latencies before first attack and first ingestion and (3) increasing attack efficiency. In addition, there was a significant increase in the number of S. umbra individuals that ingested at least one prey item over the 6 training days. The percentage of fish that ingested at least one prey item did not, however, increase significantly for D. dentex individuals over this period; instead juveniles either (1) attempted to eat novel prey, succeeded and displayed an improvement of their feeding efficiency through training, or (2) did not forage or eat over the 6 training days. The high number of individuals exhibiting the second response could be linked to several factors, including fear, personality or the type of prey used in this study. In S. umbra , individuals from the [50–60[ mm total length size class outperformed other size classes. Our findings highlight differences in feeding behaviour between the two species and the positive impacts of training on feeding performance. Our results should be taken into account when developing release protocols for potential restocking programmes. • Training had a positive effect on feeding performance of both species. • Nearly all Sciaena umbra juveniles ate at least one prey after 6 days of training. • A majority of Dentex dentex juveniles did not eat prey during all tests. • S. umbra from the [50–60[ mm size class exhibited better feeding performance. [ABSTRACT FROM AUTHOR]

Swimming performance is a well‐established key physiological parameter of fish that is highly linked to their fitness in the wild. In the context of fish restocking purposes, it therefore appears crucial to study this specific behaviour. Here, the authors investigated intra and interspecies differences in the swimming performance of hatchery‐reared post‐larvae and juveniles belonging to two Mediterranean candidate threatened species, the common dentex, Dentex dentex (Sparidae), and the brown meagre, Sciaena umbra (Sciaenidae), with body sizes ranging from 8 to 37 mm total length (TL, from 24 to 58 days post‐hatch). The swimming abilities were estimated through the calculation of their critical swimming speed (Ucrit), their relative Ucrit and their Reynolds number (Re). Two different patterns were observed between D. dentex and S. umbra, showing a different effect of ontogeny on the performance of both species. The relative Ucrit of S. umbra decreased linearly through ontogeny, whereas the relative Ucrit and Ucrit of D. dentex increased linearly through the range of sizes tested. The ontogenetic change in Ucrit of S. umbra occurred in two stages: a first stage of sharp improvement and a second stage of a slow decrease in performance. Both stages were separated by a breakpoint that coincided with the appearance of a refusal to swim behaviour that occurred shortly after the end of metamorphosis and can potentially be associated with the establishment of this species sedentary behaviour. The swimming performance of both species showed ontogenetic differences. Sciaena umbra had the highest relative performance when its body sizes were the smallest, whereas D. dentex showed the highest relative performance when its body sizes were the largest. These results will be linked to future research on both of these species concerning their escape, exploratory and predatory behaviours, and for restocking purposes to draw a more realistic overview of hatchery‐reared juvenile performance. Knowledge of both species' behavioural and swimming performance through ontogeny is important to consider when using hatchery‐reared fish juveniles for restocking, as size‐at‐release can have a large impact on fish survival and thus on restocking success. [ABSTRACT FROM AUTHOR]

The common dentex (Dentex dentex (Linnaeus, 1758)) is an iconic fish in the Mediterranean diet. Due to its commercial and organoleptic importance, this sparid is highly appreciated in European markets and is often subjected to species substitution frauds. Comparative mitogenomics is a suitable approach for identifying new and effective barcode markers. This study aimed to find a molecular tag useful for unequivocally discriminating the sparid species D. dentex. The comparison of the complete mitochondrial DNA (mtDNA) sequences of 16 sparid species allowed us to highlight the potential of the NAD2 gene for direct identification purposes. Common dentex-specific primers were created and successfully evaluated by end-point and real-rime PCR (Polymerase Chain Reaction) for several fish species, achieving amplification only in the D. dentex. The method proposed in this study appears fast, simple, and inexpensive and requires affordable instrumentation. This approach provides unambiguous results for the common dentex authentication without the sequencing step. The presence/absence assay for D. dentex can be executed in a few hours of lab work. Therefore, national authorities responsible for food safety and traceability could apply and make full use of DNA-testing methods for deterring operators from false seafood declarations.

This study focuses on reproductive biology in female Dentex dentex, which is a summer multiple spawner with the spawning period extending from late April to June. Females with body length over 35 cm were mature. The GSI value had peak values during May and June. The ova diameter ranged over nine groups (50–700 μm). The relative fecundity ranged from 510 to 1276 eggs per g gutted weight and from 20,409 to 22,595 eggs per 1 cm total length. The histological appearance of the ovarian cycle was divided into five periods. The histological structure of the maturing and ripe oocyte wall shows the presence of five different layers. Baseline of testosterone and estradiol levels was found during the immature and spent, whereas the peak value was found in prespawning and ripe-spawning period. While the maximum total lipid content was in the maturing ovary, the minimum was in muscles of prespawning female. The main polyunsaturated fatty acids n-3 (PUFA) for ovary, liver and muscles were docosahexaenoic (DHA, 22:6 n-3) and eicosapentaenoic (EPA, 20:5 n-3) acids, whereas n-6 (PUFA) were linoleic (18:2 n-6) and arachidonic (20:4 n-6). All together, the present observations gave basic data of the reproductive cycle of female D. dentex required for its successful spawning.

The present study focuses on reproductive biology parameters and histological and fine structure investigations of testes maturation, in respect to steroid hormones and fatty acids’ profile. All males over 30 cm in length were found to be mature. Gonadosomatic index (GSI) of males increased progressively to reach a peak value in May and June. In Dentex dentex, the spermatogonia were detected throughout the year in the peripheral zone of the testes. Spermatocytes are characterized by large nuclei with higher electron density and a layer of cytoplasm. The nuclei of spermatids were characterized by a condensed chromatin material. The early spermatid had a central nucleus and a large number of mitochondria. One big mitochondrion lies beneath the head of the sperm. The seasonal change of serum testosterone correlates with gonadal development. The presence of nearly ripe and ripe male D. dentex coincides with the surge of testosterone and the decrease in estradiol continues throughout the spawning periods. In males, higher GSI was accompanied by the highest lipid content of the testis. The high concentration of polyunsaturated fatty acids n-3 (PUFA) for testis, liver and muscles was as follows: docosahexaenoic (DHA, 22: 6 n-3) and eicosapentaenoic (EPA, 20:5 n-3) acids. The higher concentration of polyunsaturated fatty acids n-6 (PUFA) for testis, liver and muscles was as follows: linoleic (18:2 n-6) and arachidonic acids (20:4 n-6) with significant differences in relation to maturation stages at (P

The common Dentex (Dentex dentex, Linnaeus 1758) has a significant economic importance and is a highly valued table fish in the Mediterranean region. The paucity of genetic information relating to sparids, despite their growing economic value, provides the impetus for exploring the mitogenomics of this fish group. Here, we sequenced D. dentex complete mitochondrial genome. The sequence is comprised of 16,652 bp and consists of 13 protein-coding genes, 2 rRNA genes, 22 tRNA genes and a 2 non-coding regions (D-loop and L-origin). The overall nucleotide composition is: 27.5% of A, 28.7% of C, 26.9% of T, and 16.9% of G.

As the world's fastest ongrowing sector in food production, aquaculture has remarkable priority and needs technological improvements and new candidate fish species to overcome some limitation factors. Considering these issues, this study based on determining the flesh quality in terms of nutrient and mineral element composition of two potential fish species, common dentex (Dentex dentex) and greater amberjack (Seriola dumerili), in recirculation aquaculture system (RAS). On the nutrient basis, the dry matter content of 28.82% and fillet yield with a value of 53.28% of Dentex dentex were found significantly higher than (P<0.05) Seriola dumerili. Crude protein and lipid values demonstrated slight but insignificant differences between the species. Among the macro elements of K and Mg and micro elements of Cr, Mn and Ni were noticeably higher in common dentex than greater amberjack, but Zn level was present almost double amount in amberjack (P<0.05). [ABSTRACT FROM AUTHOR]

Larval fish have a relatively poorly developed immune system and hence they primarily rely on non-specific immune responses produced in the skin and gut. This study aims to illustrate the fine structure of gut development in common dentex (Dentex dentex) larvae and determine the initiation of pinocytic activity, which is an important early non-specific immune response in fish intestines, during various live-food feeding stages (yeast enriched rotifer, Artemia nauplii and metanauplii) from hatching (D0) to 25 days after hatching (D25) by using transmission electron microscopy (TEM). A total of 54 larvae were sampled and examined with electron microscopy. The results show that hind-gut intestine enterocytes have morphological features which suggest they play a role in absorption and intracellular digestion of nutrients in fish. The presence of vigorous pinocytic activity in the Artemia feeding stage between 17-25 days after hatching is evidence for the development of a nonspecific immune system. In the present study, the ultrastructural gut development of cultured common dentex was investigated for the first time and the data reported in this study may provide additional fundamental knowledge for improving larval rearing success in common dentex culture. [ABSTRACT FROM AUTHOR]

Abstract The egg quality of two common dentex captive broodstocks were monitored for two consecutive years during their natural spawning season. Volume of spawned eggs, volume of buoyant eggs, fertilization rate, egg weight, hatching rate and mortality of larvae were recorded. According to the volume of spawned eggs, the ratio of buoyant eggs spawned, the number of spawning days and the fertilization rate pointed to an improvement from Year 1 to Year 2. But data on hatching rate and larval mortality lead to the opposite conclusion. Highlights • Two common dentex captive broodstocks have been monitored during their natural spawning season for two consecutive years. • The quality of the spawned eggs has been assessed using different quality criteria based on egg production or larval performance. • Criteria used for assessing the spawning quality lead to different conclusions. • In conclusion, all criteria should be used in order to obtain a reliable assessment, including criteria based on larval performance. [ABSTRACT FROM AUTHOR]

This study focuses on reproductive biology in female Dentex dentex , which is a summer multiple spawner with the spawning period extending from late April to June. Females with body length over 35 cm were mature. The GSI value had peak values during May and June. The ova diameter ranged over nine groups (50–700 μm). The relative fecundity ranged from 510 to 1276 eggs per g gutted weight and from 20,409 to 22,595 eggs per 1 cm total length. The histological appearance of the ovarian cycle was divided into five periods. The histological structure of the maturing and ripe oocyte wall shows the presence of five different layers. Baseline of testosterone and estradiol levels was found during the immature and spent, whereas the peak value was found in prespawning and ripe-spawning period. While the maximum total lipid content was in the maturing ovary, the minimum was in muscles of prespawning female. The main polyunsaturated fatty acids n-3 (PUFA) for ovary, liver and muscles were docosahexaenoic (DHA, 22:6 n-3) and eicosapentaenoic (EPA, 20:5 n-3) acids, whereas n-6 (PUFA) were linoleic (18:2 n-6) and arachidonic (20:4 n-6). All together, the present observations gave basic data of the reproductive cycle of female D. dentex required for its successful spawning. [ABSTRACT FROM AUTHOR]

The present study focuses on reproductive biology parameters and histological and fine structure investigations of testes maturation, in respect to steroid hormones and fatty acids’ profile. All males over 30 cm in length were found to be mature. Gonadosomatic index (GSI) of males increased progressively to reach a peak value in May and June. In Dentex dentex , the spermatogonia were detected throughout the year in the peripheral zone of the testes. Spermatocytes are characterized by large nuclei with higher electron density and a layer of cytoplasm. The nuclei of spermatids were characterized by a condensed chromatin material. The early spermatid had a central nucleus and a large number of mitochondria. One big mitochondrion lies beneath the head of the sperm. The seasonal change of serum testosterone correlates with gonadal development. The presence of nearly ripe and ripe male D. dentex coincides with the surge of testosterone and the decrease in estradiol continues throughout the spawning periods. In males, higher GSI was accompanied by the highest lipid content of the testis. The high concentration of polyunsaturated fatty acids n-3 (PUFA) for testis, liver and muscles was as follows: docosahexaenoic (DHA, 22: 6 n-3) and eicosapentaenoic (EPA, 20:5 n-3) acids. The higher concentration of polyunsaturated fatty acids n-6 (PUFA) for testis, liver and muscles was as follows: linoleic (18:2 n-6) and arachidonic acids (20:4 n-6) with significant differences in relation to maturation stages at ( P < 0.001). [ABSTRACT FROM AUTHOR]

The common dentex Dentex dentex (Linnaeus, 1758) is an iconic marine coastal fish in the Mediterranean Sea. It is a demersal sparid fish (0-200 m), that grows to a maximum length of 100 cm and a weight of 13 kg, with a relatively long life span (more than 20 years). As a high trophic level predator, it holds a key position in coastal marine food webs. The common dentex is of great economic importance for both artisanal (small-scale coastal fisheries) and recreational fishing. Despite its economic and ecological importance, scientific data on this species in its natural environment are still very scant. The global commercial catch of common dentex has fluctuated over the last 60 years on an interannual time scale, and has declined significantly since the 1990s. There are few data regarding fishing effort and total catch from recreational fishing for common dentex, but it appears that this species is particularly targeted by this activity. The common dentex is now classified as 'vulnerable' in the Red List of Threatened Species in the Mediterranean Sea. This review summarizes the current literature on D. dentex in regard to biology, ecology, parasitology, population structure, commercial and recreational fishing, and management regulations. Future research directions to fill gaps in current knowledge are suggested. [ABSTRACT FROM AUTHOR]

This study represents the initial attempt to evaluate the effect of egg protein-bound amino acid (i.e., vitellogenin-derived PAAs) content on embryo/larva success in Dentex dentex. Viable eggs were ob-tained from a single female (i.e., intra-individual analysis) in captivity. Selected embryo/larva viability parameters (the egg floating rate, the hatching rate, and the larval survival rate at days 0 to 5 post-hatch) were determined. The egg batches were categorised in three groups (high-, medium-, and low-quality batches) based on the magnitude of their hatching rates. The protein-bound amino acid content of biometrically similar egg batches of varying quality was analysed. The content values for 12 protein-bound amino acids (i.e., essential PAAs: Thr, Met, Arg, lie, Val, Phe, His; non-essential PAAs: Ala, Glu, Gly, Asp, and Ser) were significantly correlated with the embryo/larva viability parameters in an analysis performed in terms of their ratios. The egg protein-bound amino acid content was signif-icantly correlated with the dentex larval survival rate at 3 and 5 days post-hatch, a critical period of survival that is problematic during the propagation of this species in captivity. The results of this study also offer statistical evidence for the effects of the interrelationships of the egg protein-bound amino acids on the relationships between the quantitative composition of the protein-bound amino acids and the viability parameters. [ABSTRACT FROM AUTHOR]

The particular metabolic strategies of the common dentex ( Dentex dentex) to face a period of prolonged starvation and subsequent refeeding were assessed. Plasma metabolites, endogenous reserves, and the activity of key enzymes of intermediary metabolism in liver, white muscle, and heart were evaluated. Plasma glucose, total lipid, triglycerides, total-, HDL- and LDL-cholesterol, and protein levels, liver, and white muscle glycogen, and perivisceral, and muscle fat were significantly reduced by starvation, whereas liver lipid content was surprisingly increased. Those enzymes involved in phosphorylation and oxidation of glucose and lipid synthesis, as well as alanine aminotransferase activity, were significantly depressed in liver of starved fish. The increase in β-hydroxyacyl-CoA dehydrogenase (HOAD) indicated an enhanced fatty acid oxidation during starvation. Part of the acetyl-CoA generated by β-oxidation was oxidized in the hepatic Krebs cycle, as reflected the increased citrate synthase (CS) activity. The oxaloacetate required for the reaction catalized by CS activity would be supplied by aspartate aminotransferase (ASAT) activity whose activity was also enhanced. Glutamate dehydrogenase also increased to deaminate the glutamate produced by transaminases, especially by the increased ASAT activity. Liver gluconeogenesis of starved fish was maintained at the same rate that in controls, with glycerol playing an important role as glucogenic substrate. The increased hepatic β-hydroxybutyrate dehydrogenase (β-OHBDH) activity indicates that part of the acetyl-CoA arriving from β-oxidation was being diverted for ketone bodies production with dentex liver playing an important role in providing ketone bodies as fuels for other tissues under such circumstances. Most enzyme activities in white muscle of starved dentex were significantly depressed. In heart, starvation induced an important inhibition of those enzymes involved in glucose and protein metabolism, whereas CS, HOAD, and β-OHBDH activities were maintained at control levels. Although several biomarkers assayed returned to control values after refeeding, many others did not, which indicate that after 3 weeks of refeeding, pre-starved dentex is still experiencing a transient period of metabolic adjustments directed toward the restoration of body mass. [ABSTRACT FROM AUTHOR]

Abstract: The ultrastructural organization of the female reproductive system of Metadena depressa, digenean intestinal parasite of Sparidae (Dentex dentex), was investigated by electron microscopy. The vitellogenesis is divided into four stages: stage I, vitellocytes have a cytoplasm mainly filled with ribosomes and few mitochondria; stage II, beginning of the synthetic activity; stage III, active shell globule clusters synthesis; stage IV, mature vitellocytes are filled with shell globule clusters and generally contain several large lipid droplets. Glycogen granules are grouped at the periphery of the cell. The three stages of the oogenesis process take place in the ovary: stage I, oogonia are undifferentiated small cells located at the periphery of the organ; stage II, primary oocytes possess a higher nucleo-cytoplasmic ratio and a nucleus with a nucleolus and synaptonemal complexes indicating the zygotene-pachytene stage of the first meiotic division; stage III, mature oocytes are located in the proximal region of the organ and possess a cytoplasmic chromatoid body and cortical granules in a monolayer close to the periphery of the cell. [Copyright &y& Elsevier]

Abstract: The ultrastructural organization of the spermatozoon of a cryptogonimid digenean, Aphallus tubarium, a parasite of Dentex dentex, is described. The spermatozoon possesses the elements found in other digeneans: two axonemes with 9+“1” pattern, a mitochondrion, a nucleus, cortical microtubules, external ornamentation and spine-like bodies. However, the mitochondrion appears as a cord with a bulge; this characteristic has never been described in other studied cryptogonimid and in other digeneans except in one lepocreadiid, Holorchis micracanthum. Likewise, the presence of a thin cytoplasm termination in the anterior part of the spermatozoon has never been pointed out in the cryptogonimids. [Copyright &y& Elsevier]

Abstract: Since the timing of the lipovitellin heavy chain (LvH) of vitellogenin Ab (VtgAb) degradation during marine teleosts ontogeny is poorly understood, the current study was planned to address some aspects of this shortcoming. Fertilized eggs (before epiboly) of Dentex dentex were analysed. Vtg-derived proteins, that appeared as 6 protein bands after SDS-PAGE, were purified using specific ion exchange chromatography. Five bands (i.e., ∼78, ∼57, ∼22, ∼19, and ∼17 kDa) were merely stained with Coomassie Blue and one band (i.e., ∼16 kDa) only with Periodic Acid Schiff (PAS). The ∼16 kDa protein band was subjected to a mass spectrometry-based sequencing. These results showed that the ∼16 kDa protein band contains a mixture of “LvH-Ab” derivatives with the same molecular weight. The specific staining system (i.e., PAS) also revealed the glycosylation of some of the LvH-Ab fragments inside the ∼16 kDa protein band. The study provides new data about fragmentation of the LvH-Ab in marine pelagophil teleosts. [Copyright &y& Elsevier]

Abstract: Free amino acids (FAAs) play a key role in the physiology of marine teleosts (eggs, embryos, and larvae). However, the relationship between the egg FAAs content and the production of viable embryos and larvae (at different developmental stages) in batch spawner pelagophils has not yet comprehensively been investigated. Viable eggs of common dentex, Dentex dentex, were obtained from captive broodstocks. Egg wet weight (WW), dry weight (DW), and water content (%W) and viability parameters, or VPs (egg floating rate [FR], hatching rate [HR], and larval survival rate [SR] at days 0 to 5 posthatch) were determined for 45 egg batches. The egg batches were classified according to their HR magnitude. Twelve egg batches with the same WW, DW, and %W were taken from the same broodstock and at the same developmental stage to determine the qualitative and quantitative composition of FAAs. The total FAA (TFAA) content, glutamic acid (Glu), asparagine (Asn), glutamine (Gln), and arginine (Arg) were correlated with VPs. The Glu was significantly correlated with HR and SR at 0 day posthatch (dph), the Asn with SR at 1 dph, and the Gln and Arg with FR and HR. Of the 361 ratios made based on the absolute concentrations of FAAs, 24 ratios were correlated with VPs (P < 0.005) through 42 simple regression models (R2 =0.641 to 0.846). Of the 42 significant relationships found ∼10%, ∼28%, ∼12%, ∼30%, ∼8%, ∼4%, ∼2%, ∼2%, and ∼2% of the models show the relations of the egg FAAs ratios with FR, HR, SR at days 1 to 5 posthatch, and %W, respectively. A path coefficient in combination with a Pearson''s correlation coefficient provided a series of statistical evidences to show the effects of the egg FAAs interrelations on the relationships found between quantitative composition of a FAA and a VP. [Copyright &y& Elsevier]

Abstract: Digestive physiology of on-growing common dentex (Dentex dentex), including protease, amylase and lipase activity in stomach, pyloric caeca, anterior and posterior intestine, was evaluated. The influence of dietary macronutrient balance on these digestive processes was also assessed. Four experimental diets with different protein:lipid:carbohydrate ratios (43/16/28; 43/24/4; 38/19/28 and 38/24/13) were formulated. The highest activity for acid proteases was located in the stomach at pH 1.5. Alkaline proteolytic activities showed the highest values in the pyloric caeca and posterior intestine at pH 8.5–9.0. Dentex showed substantial amylase activity in the pyloric caeca and posterior intestine. Lipase activity was higher in the pyloric caeca, anterior and posterior intestine and was not detected in the stomach. Feed composition influenced alkaline protease activity in the anterior and posterior intestine and was higher for the diet with less protein and more carbohydrates. Enhanced amylase activity was observed in the pyloric caeca and posterior intestine in those groups fed on higher carbohydrate and lower lipid level diets. High dietary carbohydrate levels produced the highest lipase activity but this only occurred in the anterior intestine. We can conclude that the digestive tract of dentex adapts well to protein digestion and possesses a high potential for digesting the other dietary macronutrients, too. Dietary carbohydrate content seems to induce changes in protease, amylase and lipase activity. [Copyright &y& Elsevier]

Abstract: The aim of this study was to assess the potential effects of replacing part of the dietary protein by lipid or carbohydrate on the characteristics of dentex muscle. Dentex were hand-feed four isoenergetic diets (22.6 MJ kg−1 gross energy) with protein:lipid:carbohydrate ratios 43/16/28 (D1); 43/24/4 (D2); 38/19/28 (D3), and 38/24/13 (D4). At the end of the feeding period, biometric parameters, textural properties of muscle, as well as protein, lipid and collagen contents, and electrophoretic protein profiles of this tissue were studied. The decrease in dietary protein content improved textural parameters (increased firmness and water holding capacity). Within each dietary protein level, diets with high carbohydrate and low lipid contents resulted in lower values of muscle firmness than diets with low carbohydrate and high lipid contents. This increase in firmness matched with a lower muscle lipid and higher muscle collagen contents. SDS-PAGE separation of muscle extracts showed a higher relative contribution of myosin to total optical density in muscle from those animals fed lower dietary protein, although no significant difference in fish texture could be attributable to this finding. Results indicate a favourable effect of replacing protein by alternative energy sources (lipids or carbohydrates) on the rheological properties of muscle in this species, this improvement was more noticeable when protein was replaced by lipid than by carbohydrate. [Copyright &y& Elsevier]

Larvae of two Mediterranean Sparidae species, Sparus aurata and Dentex dentex, were used to test the efficacy of a peroxide-based product (Ox-Aquaculture©) on the reduction in bacterial load in larval rearing water and its effects on larval survival. Eleven-day-old S. aurata larvae and 15-day-old D. dentex larvae were exposed to different concentrations of Ox-Aquaculture© (50, 100 and 200 mg L−1, and 20 and 50 mg L−1 respectively) for 1 h. Results indicated that 50 and 20 mg L−1 were the most effective concentrations for the reduction in bacterial load (at least one order of magnitude) after 1 h treatment, without affecting larval survival and/or vitality in 11 dph S. aurata and 15 dph D. dentex larvae respectively. Ox-Aquaculture© concentrations of 200 and 50 mg L−1 during 1 h affected negatively final survival rate of the larvae of S. aurata and D. dentex respectively. [ABSTRACT FROM AUTHOR]

The aim of the present study was to set up reference intervals for biochemical parameters in new candidate species of Mediterranean marine fish culture—striped sea bream, Lithognathus mormyrus and common dentex, Dentex dentex as well as traditionally cultured species—gilthead sea bream, Sparus aurata. The reference biochemical values were assessed for plasma cortisol, glucose, Ca, inorganic P, Na, K, Cl, C-reactive protein, hematocrit, and prothrombin time. The biochemical reference values established may allow important physiological decision in adaptation process of striped sea bream and common dentex as well as provide contribution to our present knowledge on gilthead sea bream physiology. [ABSTRACT FROM AUTHOR]

Total lipid content, fatty acid (FA) composition and lipid class composition of common dentex eggs spawned at different times and larvae reared under different culture conditions until 40 days posthatch (dph) were analysed to get a general pattern of lipid composition during larval development. Two groups of larvae were kept under starvation to compare their FA composition with that obtained from normally fed larvae. To compare FA use or accumulation during larval development, results were grouped according to the developmental stage of the larvae instead of age in days posthatch. Saturated and monounsaturated FAs decreased along larval development, while polyunsaturated fatty acid (PUFA) content increased. The ratio of docosahexaenoic acid (DHA)/eicosapentaenoic acid shifted from 4 to 5 in early developmental stages to lower than 1 after metamorphosis. Arachidonic acid levels remained constant along larval development. Larvae kept 6 days under starvation consumed most of their n-3 PUFA while conserving the DHA to values at day 0. The results presented here are useful for the design of nutritional experiments, because there were differences detected in terms of lipid and FA composition between developmental stages with higher differences mainly found in first-feeding larvae and early developmental stages. [ABSTRACT FROM AUTHOR]

The shape of the lipid vesicle (the ratio between the maximal and the minimal diameter and the shape coefficient) of the eggs of Diplodus puntazzo and Sparus aurata is correlated with larval survival rate (%) and can be used as an egg quality marker as reported previously by Lahnsteiner and Patarnello (2005) . In the present study, this method for egg quality determination has also been validated for common dentex, Dentex dentex, after introducing several modifications in the calculation and evaluation procedure in order to obtain higher sensitivity. In the present study, it could be demonstrated that the shape of the lipid vesicle is not only correlated with the hatching rate but also with the survival rate of 1, 2 and 3 days post hatch larvae and therefore it can also be used as an indicator of larval viability at early stages of development. [ABSTRACT FROM AUTHOR]

Abstract: This study established different oxygen level categories (optimal, sub-optimal, dangerous and lethal) for Dentex dentex according to ventilatory frequency (V f) and oxygen consumption (MO2) in response to gradually decreasing dissolved oxygen levels for different fish masses (117–745 g) and water temperatures (13.9–28.1 °C). Initial and maximum ventilatory frequency (V f0 and V fmax, respectively) and oxygen saturation at which ventilatory frequency was altered (S Vf) ranged from 31.3 to 71.3 beats/min, 58.0 to 129.7 beats/min and 48.1 to 81.7%, respectively. D. dentex maintained a constant MO2 rate, until a critical oxygen saturation (S crit) was reached. The S crit and lethal oxygen saturation (LS50) ranged from 26.5 to 40.6% and 12.3 to 18.9%, respectively. V f0, V fmax, S crit and LS50 were correlated positively and significantly with temperature, but only V fmax was correlated with body mass, pointing to a higher V f response in small than large fish. In the range of fish masses and temperatures tested, our findings suggest an optimal dissolved oxygen saturation of above 70–75% (constant V f and MO2), a sub-optimal value of between 70 and 35% (altered V f but not MO2), with anything below 35% being dangerous (altered V f and MO2). We conclude that suitable oxygen levels for D. dentex are similar with respect to other species of interest in aquaculture. [Copyright &y& Elsevier]

The early life history of common dentex (Dentex dentex L. 1758) was investigated under culture conditions. The percentage of fertilized buoyant eggs was generally high, between 80 and 85%. Egg diameters ranged from 0.938 to 1.089 mm. Larval development, growth, and some morphological changes were described from day 0 to day 32. Larvae were reared intensively in 6 m3 tank under a constant photoperiod (24 h light), and fed initially on rotifers, followed by Artemia nauplii and Artemia metanauplii. A green water technique was applied using Nannochloropsis sp., Chorella sp., and Isochrysis sp. at a density of 150,000-200,000 cells ml-1. First feeding began on day 6. Larvae completed yolk absorption on day 8 after hatching at 136 ºC cumulative temperature (day/degrees). Swimbladder inflation occurred between day 5 and day 7 post-hatching. Notochord flexion started on day 23 at 7.01 mm total length. Metamorphosis from larval to juvenile stage occurred between days 23 and 32 post-hatching at a mean total length of 12.7 mm. [ABSTRACT FROM AUTHOR]

In the current paper we present the rearing methodology of common dentex (Dentex dentex), a promising candidate for Mediterranean marine aquaculture, from the larval to the on-growing phase. The results are discussed in terms of the efficiency of rearing methodology followed, for the mass production of the species. [Copyright &y& Elsevier]

This paper reports the results of an experiment to determine whether sex ratio has any effect on the spawning efficiency of common dentex, Dentex dentex, broodstock. The paper also reports preliminary data on diurnal changes in water concentrations of steroids (measured on two separate occasions) in the same groups of fish. These latter observations were made to determine whether, using a non-invasive procedure, it was possible to relate hormonal changes in the fish to the “success of spawning.” Mature fish were placed in broodstock tanks at three different sex ratios (Group A, 4♀:1♂; Group B, 1♀:1♂; and Group C, 1♀:4♂) and regularly monitored for egg production. At 18 days after the start of spawning, water samples were removed from all three tanks at 130 min intervals over a period of 24 h. At the end of spawning, water samples were removed at 4 h intervals. Free and conjugated steroids were extracted from the water and measured by radioimmunoassay. The highest number of eggs released, percentage of viable eggs, number of spawnings, spawning index, and relative fecundity were observed in Group B (1♀:1♂). The sex steroids testosterone (T), 11-ketotestosterone (11-KT), 17,20β-P, and 17,20β, 21-trihydroxy-pregn-4-en-3-one could be readily detected in water from all tanks. Concentrations of the conjugated forms (sulphate and glucuronide) were higher than those of the free form—with the exception of sulphated T and 11-KT. The concentrations of glucuronidated 17,20β-P, sulphated 17,20β-P, and free T appeared to be associated with the number of females in the tank and glucuronidated 11-KT concentrations with the number of males. In the first set of water samples (taken during the spawning period) there was also evidence for a cycle in steroid release with an acrophase during the afternoon and early evening, a few hours before the actual act of spawning. We were not able to show any association between steroid concentrations and success of spawning. However, since the data were derived from a “snapshot” of just a single day in what was a prolonged spawning period, this was perhaps not surprising. The results from the present study will help us to design experiments that are more able to answer this question. [Copyright &y& Elsevier]

The present study describes histological and histochemical aspects of Dentex dentex larval development up to day 36 after hatching and provides a tabular overview on the ontogeny of structures involved in general metabolic processes, mechanisms of defence against disease and, particularly, nutrition. Observations are related to main developmental stages defined on the basis of external morphological features. During stage 1, the mouth and the anus of the larvae are still closed. Stage 2 starts when the mouth opens and stages 3 and 4 are characterized by the appearance of opercular spines and notochord flexion, respectively. During the first three stages, dentex larvae undergo intense organogenesis, this being particularly intense during stages 2 and 3. Stage 4 is not characterized by the appearance of new structures but by the increase in size and complexity of pre-existing ones. During stage 1, the larva acquires morphological and enzymatic equipments (hepatocytes with glycogen stores, pancreatic cells with first zymogen granules, enterocytes with microvilli, non-specific esterase and alkaline and acid phosphatase activities) which will ensure absorptive and digestive processes before the mouth opening. Pronephric excretory structures and a tubular heart are present at hatching and endocrine elements (corpuscles of Stannius, endocrine pancreas and thyroid gland) appear. During stages 2 and 3, food capture as well as digestive and absorptive processes become fully guaranteed (pharyngeal as well as mandibular teeth and taste buds appear and then proliferate, the gut progressively differentiates, the mucosa folds, ATPase and aminopeptidase M activities appear, mucus secretion establishes, particularly in the oesophagus, and at the end of stage 3, gastric glands differentiate). Before this last event occurs, acidophilic supranuclear vesicles are seen in the hindgut enterocytes and disappear at the moment the stomach develops. Gill slits are evident at initial stage 2; filaments start differentiation by the end of this stage and lamellae appear by the second half of stage 3. By this time compartmentalisation of the heart is completed, trabeculae being evident in the ventricle, and mesonephric excretory structures appear. During stage 4, gastric glands proliferate, rodlet cells appear in the stomach and the oesophagus and rodlet and goblet cells proliferate in the intestine; gill filaments and lamellae increase in number and length and there is a notable development of the mesonephros. The lymphoid organs, which appear in the sequence pronephric kidney (present at stage 1), spleen (observed at stage 2) and thymus (first seen at stage 3) remarkably increase in size during this stage. [Copyright &y& Elsevier]

Dentex is considered suitable for aquaculture due to its ready adaptation to culture systems, acceptance of formulated feeds and rapid growth rates. However, little information on the nutritional requirements or growth rates under controlled conditions has been reported for this fish. Thus, two feeding trials were performed, at different growth stages, to identify suitable protein and lipid (energy) levels to be used in formulating dry diets for this species. As the first step, a 3×2 factorial experiment was conducted to determine the optimum protein-to-energy (P/E) ratio for fingerling dentex. Triplicate groups were fed to satiation one of six practical diets with increasing levels of protein (50%, 53% and 57% DM) and two energy levels (20 and 22 kJ g-1) within each protein level. Protein utilization was enhanced by a sparing effect of dietary lipid at 19.7%. These data suggest that, when the energy level of the diet is maintained at 22 kJ g-1, the dietary protein level for fingerling dentex can be lowered from 57% to 50%. In the second experiment, with larger fish, triplicate groups of fish were fed one of six diets with two energy levels (20 and 22 kJ g-1) and three P/E ratios (19, 21 and 23 g MJ-1). Thus, the dietary protein level tested ranged from 38.7% to 51.14% DM. The results in the second trial suggest that, when protein efficiency or retention are considered, even dietary levels of 43.4% CP and 19 g protein MJ-1 of P/E, and a calculated available energy level (22 kJ g-1) could be assumed to be adequate levels for formulating practical diets for this species at this growth stage. It can be concluded that, for the two size classes of dentex used, dietary lipid had a protein-sparing effect. [Copyright &y& Elsevier]

Abstract The effects of different levels of illumination on common dentex Dentex dentex (L.) larvae have been examined. Illumination affected the relationships between total length and digestive tube length, total length and oil globule volume, and total length and yolk sac. The relationship between total length development and yolk sac utilization in dark and light conditions was found to be significant (P<0.05). However, it was determined that the relationship between digestive tube development and oil globule absorption was not significant (P>0.05). Besides, there is no effect of different light intensities on absorption of yolk sac and oil globule and digestive tube development (P>0.05). In addition, total length development was not significant (P>0.05). Survival rate was found to be not significantly different in dark conditions (P>0.05). [ABSTRACT FROM AUTHOR]

Dentex fingerlings weighing 2.5 g initial live weight were fed 12 extruded diets containing four crude protein levels (40%, 45%, 50% and 55%) and three crude lipid levels (12%, 17% and 22%) according to a factorial design, for 6 weeks. Survival was high (84–92%) and specific growth rate (SGR) values were 3.4%, 3.9%, 4.3% and 4.1% day−1 and food conversion ratio (FCR) were 2.2, 2.1, 1.5 and 1.9 for fish fed the diets containing 40%, 45%, 50% and 55% crude protein, respectively. With respect to lipid levels, SGR values were 4.2%, 4.0% and 3.6% day−1 and FCR were 1.7, 1.8 and 2.3 for 12%, 17% and 22% crude lipid, respectively. The effects of protein and lipid levels were significant; final live weight, SGR, FCR and PER values were best for fish fed 50% crude protein and poorest for those fed 22% lipid diets. The best growth performance was observed in fish fed diets containing 50/12 and 50/17 protein/lipid ratios. The results indicate that optimum growth and nutrient utilisation of dentex fingerlings can be obtained when they are fed a diet containing around 50% crude protein with a lipid level ranging from 12% to 17%, and having a crude protein/gross energy ratio from 22 to 25 g MJ−1. [Copyright &y& Elsevier]

The formation of annuli was examined from scales and otoliths of farmed (known age) common dentex, Dentex dentex. One scale annulus formed each year during May and one hyaline zone on the otoliths during June. The formation of scale annuli and the hyaline zone on otoliths of adult fish coincided with gonadal maturation which takes place during April to May. Scales were found to be more accurate than otoliths in respect to annuli formation, but their annuli were not as intense and distinct. Missing or additional hyaline zones were observed on adult otoliths. These irregularities were observed after fish maturation and were related to temperature conditions, as well as to faster growth of the farmed fish than the wild ones. [Copyright &y& Elsevier]

The effect of photoperiod and temperature on the timing and the quality of spawning, and on associated endocrine changes in circulating 17β-oestradiol, 11-ketotestoserone (11-KT) and vitellogenin (Vtg) were investigated in common dentex, Dentex dentex, undergoing their second reproductive cycle. The possibility was also explored of using the measurement of steroids in the culture water of broodstock tanks, rather than in individual blood plasma samples, as a potentially useful tool for assessing the physiological state of a fish without disturbing them. One group of fish was exposed to a simulated natural seasonal cycle and ambient temperature (CONTROL). The other two groups were exposed to simulated seasonal photoperiod cycles (12 month-long) but which were phase-shifted either three months before (ADVANCED) or after (DELAYED) the natural cycle. Temperature was kept at 19.4±0.9 °C all-year-round. In the CONTROL, spawning started in mid-April and lasted until mid-June, while in the ADVANCED group, spawning started 4 months earlier and in the DELAYED group 2 months later than the CONTROL. The total egg production, egg quality, hatching rate, relative fecundity, and spawning index of the experimental groups were similar to the controls. The differences in spawning time induced by photothermal manipulation were associated with a difference in the timing of peak concentrations of plasma E2, 11-KT and Vtg. In all three groups, the amounts of conjugated 17,20β-dihydroxy-4-pregnen-3-one (17,20β-P) and free and sulfated 11-KT which could be extracted from the water during the spawning period were significantly higher than those found in the preovulatory period. However, the differences were mostly less than 2-fold suggesting that, at least under the conditions employed in this study, the method was of limited use for non-intrusive detection of gonadogenesis and spawning (as had been hoped). The observed differences in spawning time and in the seasonal changes of sex steroids and Vtg confirm and extend the findings on marine fish. [ABSTRACT FROM AUTHOR]

A very limited number of scientific studieshave been conducted on Dentex dentex inits natural environment yet, over the lastdecade, this species has been extensivelystudied in captivity. This sparid fish, highlyregarded in many countries of the Mediterraneancoasts, has recently been successfullyproduced, on a trial basis, in Greece, Italyand Spain, and may become a serious candidatefor aquaculture. Although the species was firstconsidered as protandric, later studies havecharacterized Dentex dentex as agonochoric species with bisexual juvenilephases. In recent times, it has become possibleto control and lengthen the spawning period forthe purpose of improving production management.Embryonic and larval development has beenextensively described, and the assaying of anumber of culture conditions and feedingprotocols have permitted us to overcome thedifferent stages of larval development.Survival rates, however, are still low and thefeeding requirements at each stage, especiallyduring the weaning period, are not clearlydefined. Nevertheless, growth rate, both atlarval and fattening stages, is high whencompared to that of gilthead sea bream ( Sparus aurata).In spite of the many studiesperformed over recent years, the lack of a dryfeed precludes exploration of the full growthpotential of Dentex dentex under cultureconditions. During the larval and juvenileperiods, Dentex dentex exhibitsaggressive behaviour and high sensitivityto stress, and is prone to high mortality ratesdue to a number of pathological processes(systemic granuloma, epitheliocystis,vibriosis, etc.) [ABSTRACT FROM AUTHOR]

Digestive proteases present in two sparids, seabream (Sparus aurata) and common dentex (Dentex dentex), have been characterized using both biochemical and electrophoretic techniques. Although optimum pH and temperature for maximum activity of both acid and alkaline proteases were similar in the two species, important differences in total activity, as well as in thermal and pH stability were found. Specific inhibitors and SDS-PAGE zymograms were used to clarify such differences. Evidences support the existence of a more active and complex protease set in dentex. Results are discussed from the perspective of their application to the formulation of feeds for each species. [ABSTRACT FROM AUTHOR]