Influence of dietary administration of a probiotic strain Shewanella putrefaciens on senegalese sole (Solea senegalensis,Kaup 1858) growth,body composition and resistance to Photobacterium damselae subsp piscicida

Probiotics are currently being supplemented to cultured fish due to their benefits for fish performance. Herein, we tested the health protection and nutritional effects of probiotic Shewanella putrefaciens (Pdp11 strain), both fresh and lyophilized cells, on Senegalese sole (Solea senegalensis) juveniles. Pdp11 was incorporated into fish feed at concentration of 10⁹ cells g^?1, and then provided to juvenile sole for 2 months. Growth rates were significantly higher in fish fed the fresh probiotic compared with fish fed the control diet. Growth of fish receiving lyophilized bacteria was not improved when compared with controls. Body compositions (protein, total lipids and fatty acids profile) were similar for each dietary treatment. At the end of the study, fish were challenged by intraperitoneal inoculation with a pathogenic strain of Photobacterium damselae subsp. piscicida. Relative percentages of survival (RPS) ranged between 25% and 43.8% for fish receiving both probiotic supplemented diets. Both fresh and lyophilized Pdp11 cells conferred protection against P. damselae subsp. piscicida. However, only fresh Pdp11 enhanced Senegal sole performance. These findings should be taken into account for industry purposes in which lyophilized Pdp11 might be easier to manage.     

Granulomatous lesions in a wild mullet population from the eastern Ligurian Sea (Italy): mycobacteriosis vs. pseudotuberculosis

Mycobacterium spp. and Photobacterium damselae subsp. piscicida are recognized as the most frequent causative agents of granulomatous lesions in fish. Although frequent episodes of mycobacterial infections have been reported in wild fish worldwide, only sporadic cases have been documented to date in Italy. To investigate for the presence of lesions referable to mycobacteriosis and to identify the mycobacterial species involved, a total of 159 wild mullets were fished from the eastern coast of the Ligurian Sea, killed and necropsied. Liver and spleen samples were collected from all fish for histopathological and microbiological analyses. Molecular investigations for identification of Photobacterium damselae subsp. piscicida were performed. Gross examination revealed granulomatous lesions in one animal; microscopically, 42.14% of fish displayed granulomas with various histological features, 19.50% resulted positive at Ziehl–Neelsen staining, and were confirmed as mycobacterial lesions by culture. The identified colonies were characterized as M. fortuitum, M. abscessus, M. flavescens, M. chelonae, M. septicum and M. nonchromogenicum. In all, 35% of animals resulted positive for Photobacterium damselae subsp. piscicida. These data suggest widespread mycobacterial infection also by Photobacterium damselae subsp. piscicida infections in wild fish. Moreover, the pathogenicity of some mycobacterial species, previously considered as saprophytic, was demonstrated.     

Immune responses and gut morphology in Senegalese sole (Solea senegalensis) fed dietary probiotic supplementation and following exposure to Photobacterium damselae subsp. piscicida

The aim of this study was to determine the effect of a dietary multi‐species probiotic on growth, gut morphology and immune parameters in Senegalese sole (Solea senegalensis). Fish were fed with two experimental diets, a control diet and the same diet supplemented with the probiotic for 72 days. A sub‐lethal bath challenge with Photobacterium damselae subsp. piscicida was performed after the growth trial. Intestine and blood samples were collected to study gut structure and plasmatic immune parameters. No significant differences were found in growth performance. The analysis of gut morphology showed a significant increase in intestinal villi height of Senegalese sole fed the probiotic. Regarding circulating leucocytes, dietary probiotic supplementation increased thrombocytes levels whereas a decrease in the proportion of lymphocytes was observed. No significant differences were observed in humoural immune parameters. Bath challenge differentially affected leucocyte counts and increased peroxidase activity. This study presents the possibility of using dietary probiotic supplementation to increase Senegalese sole welfare since gut morphology was positively affected. Although the immune response after a bacterial challenge was not modulated by dietary treatment, further studies would be instrumental to unravel eventual dietary benefits on immune mechanisms.     

Development of a real‐time PCR assay for rapid detection and quantification of Photobacterium damselae subsp. piscicida in fish tissues

The availability of a rapid and accurate method for the diagnosis of Photobacterium damselae subsp. piscicida (Phdp), able to discriminate its strictly correlated subsp. damselae (Phdd), formally known as Vibrio damsela, is essential for managing fish pasteurellosis outbreaks in farmed fish. A single‐step, high‐sensitivity real‐time PCR assay for simultaneous detection and quantification of P. damselae was designed targeting partial of the sequence of the bamB gene and tested for specificity and sensitivity on laboratory‐generated samples as well as on experimentally infected seabream tissue samples. With a limit of detection (LOD) of one copy in pure bacterial DNA, the sensitivity was higher than all methods previously reported. Validation in target and non‐target bacterial species proved the assay was able to discriminate Phdd‐Phdp subspecies from diverse hosts/geographical origins and between non‐target species. In addition, two SNPs in the target amplicon region determine two distinctive qPCR dissociation curves distinguishing between Phdp‐Phdd. This is the first time that a molecular method for P. damselae diagnosis combines detection, quantification and subspecies identification in one step. The assay holds the potential to improve the knowledge of infection dynamics and the development of better strategies to control an important fish disease.     

A novel research on isolation and characterization of Photobacterium damselae subsp. damselae from Pacific white shrimp,Penaeus vannamei,displaying black gill disease cultured in China

In June 2019, massive mortalities of cultured Penaeus vannamei occurred in a local farm in Hainan Province, China. The diseased shrimp displayed evident black gills. Three bacterial strains 20190611001, 20190611007 and 20190611022 were isolated from hepatopancreas and gills of the diseased shrimp and identified as Photobacterium damselae subsp. damselae based on the sequence analysis of 16S rRNA and toxR genes. These three isolates showed haemolytic activities. Of them, strain 20190611022 isolated from hepatopancreas was selected and processed for pathogenic analysis. The calculated median lethal dose (LD₅₀) was 9.75 ± 4.29 × 10⁵CFU/g (body weight) by challenging P. vannameivia reverse gavage. The diseased shrimp displayed enlarged hepatopancreatic tubules and sloughing of epithelial cells in tubular lumens. The strain 20190611022 was also characterized by the testing of API 20NE systems and antibiotic susceptibility. The results of disc diffusion test showed that strain 20190611022 was sensitive to chloramphenicol, compound sulfamethoxazole, cefoperazone, ceftriaxone, ceftazidime and cefuroxime. To our knowledge, this is the first report of isolation and characterization of Photobacterium damselae subsp. damselae from natural diseased P. vannamei. Our findings can serve as a basis for further studies of its pathogenicity and provide technological support for disease controlling in shrimp aquaculture.     

Repeatable immersion infection with <Emphasis Type="Italic">Photobacterium damselae</Emphasis> subsp. <Emphasis Type="Italic">piscicida</Emphasis> reproducing clinical signs and moderate mortality

Pseudotuberculosis is a bacterial septicaemia caused by Photobacterium damselae subsp. piscicida in several marine fish species. Yellowtail Seriola quinqueradiata is the most sensitive fish species to this disease. The internal organs of naturally infected yellowtail exhibit whitish spots, tubercle-like tissue structures, consisting of bacterial accumulations. There have been many trials for experimental infection, however adequate method of infection that reproduces moderate mortality and primary clinical signs has not yet established. Present investigation evaluated an immersion infection method by using logarithmic culture-phase bacteria resulting in higher mortality than that using stationary culture-phase bacteria. Typical white spots on the spleen and kidney were also observed constantly in dead fish. Transmission electron microscopy and fluorescent antibody microscopy showed bacterial clusters not only in the spleen and kidney but also in the blood channels in the secondary gill filaments. These results were confirmed repeatedly by plural experiments. The use of logarithmic-phase bacteria in immersion infection is an appropriate technique to reproduce moderate mortality and primary clinical signs, which will be a reliable infection method also for the challenge test of pseudotuberculosis vaccine.     

Molecular and histopathological characterization of Photobacterium damselae in naturally and experimentally infected Nile tilapia (Oreochromis niloticus)

Mass mortality has occurred among cultured Nile tilapia, Oreochromis niloticus, on fish farms in Manzala, Dakahlia province, Egypt, in the summer season, 2019. Moribund fish were reported with deep ulcers, septicaemic lesions and sampled for bacterial isolation. In this study, most isolates were subjected to bacteriological examination, antibiotic sensitivity test, 16S rRNA gene sequencing and histopathological examination. Following isolate identification, intraperitoneal challenge of Nile tilapia with a bacterial suspension 2 × 10⁶ CFU/ml was performed. Samples from liver, spleen and kidney were collected for histological and biochemical analysis. The results showed a high similarity (99%) to Photobacterium damselae strains using phylogenetic analysis of 16S rRNA. P. damselae exhibited resistance to amoxicillin and erythromycin, as well it was highly sensitive to chloramphenicol and doxycycline. Moreover, haemorrhage, oedema, hemosiderosis and melanomacrophage activation in the liver and head kidney of infected fish were detected by light and electron microscopy. Also, significant higher levels of CAT and SOD in the spleen and head kidney, as well as the serum levels of NO were observed in experimentally challenged O. niloticus, compared to the control fish. Our data identified P. damselae for the first time from infected Nile tilapia, describing its sensitivity to a variety of antibiotics, histopathological alterations and oxidative stress impact, and it could be useful indicators for understanding P. damselae pathogenesis, which might provide a preventive efficacy for P. damselae.     

Fish photobacteriosis—The importance of rapid and accurate identification of Photobacterium damselae subsp. piscicida

MALDI‐TOF MS was tested for the identification of Photobacterium damselae subsp. piscicida on isolates grown on two media, cultured at three incubation times and applied on the target plate by the direct sample spotting (DS), by the on‐target extraction (OTE) and by the full extraction (FE) method, in triplicates. The identification of samples grown on blood agar (BA) outperformed identification on tryptic soya agar (TSA) by 0.64% for DS and OTE. The OTE gave the highest scores in both culture media, all incubation times and replicates. Reliable 24‐hr species identification was 61.54%, 84.61% and 53.85% for samples grown on TSA and identified by DS, OTE and FE, respectively. For isolates grown on BA, they were 76.92%, 96.15% and 30.77%, respectively. When identified by OTE, the 48‐hr identification was 93.58%, but for 72 hr declined to 71.79%. The reliable identification with the highest score from the first measurement was 100% only for OTE from BA (24 hr), whereas OTE from TSA gave 84.61% (24 hr), 76.92% (48 hr) and 84.61% (72 hr). The reliable MALDI‐TOF MS identification of Ph. damselae subsp. piscicida is incubation time, media, target plate preparation and replicate‐dependent.     

Genotypic diversity,and molecular and pathogenic characterization of Photobacterium damselae subsp. piscicida isolated from different fish species in Taiwan

Photobacteriosis, caused by Photobacterium damselae subsp. piscicida (Phdp), is a serious disease in marine fish species worldwide. To date, the epidemiological characterization of this pathogen in Taiwan remains limited. In this study, we collected 39 Phdp isolates obtained from different farmed fish for phenotypic and genotypic analysis. Phenotype bioassays using API-20E and API-20NE systems showed that the Phdp is a homogeneous group. However, genotyping using the pulsed-field gel electrophoresis (PFGE) technique revealed genetic variability among Phdp isolates when 13 and 11 different PFGE band patterns were obtained with SmaI and NotI as restriction enzymes, respectively. Phylogenetic analysis using 16S rDNA and the Fur gene clustered Taiwanese isolates and other species of P. damselae in the same clade. In contrast, the ToxR phylogenetic tree, a powerful discriminatory marker, separated the two subspecies. Furthermore, the virulence-associated genes, AIP56, P55, PDP_0080, Sod and Irp1, were detected from all isolates. Virulence testing with nine representative isolates in cobia (Rachycentron canadum) and Asian sea bass (Lates calcarifer) showed that some were highly pathogenic with 80%–100% mortality rates. This study provides epidemiological data of Phdp infections in farmed fish in Taiwan, which is necessary to develop comprehensive prevention and control strategies for the disease.     

In Vitro Antibacterial Activity of Plant Ethanolic Extracts against Fish Pathogens

Fifteen commercial ethanolic extracts from medicinal plants were in vitro screened for antibacterial activity against Listonella anguillarum (serotypes O1 and O2), Yersinia ruckeri, Photobacterium damselae subsp. piscicida, and Lactococcus garvieae. Their antimicrobial potential was assessed by the disc diffusion assay, then minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) were established by the broth microdilution method. The extracts of lavender, Lavandula officinalis; lemon balm, Melissa officinalis; basil, Ocimum basilicum; oregano, Origanum vulgare; rosemary, Rosmarinus officinalis; common sage, Salvia officinalis; and red bilberry, Vaccinium vitis‐idaea, showed a broad spectrum of inhibitory effects. The extracts of yarrow, Achillea millefolium; arnica, Arnica montana; marigold, Calendula officinalis; Icelandic lichen, Cetraria islandica; horsetail, Equisetum arvense; grindelia, Grindelia robusta; java tea, Orthosiphon stamineus; and thyme, Thymus vulgaris, were less or not active. P. damselae subsp. piscicida was the most susceptible bacterial strain, while Y. ruckeri was the most resistant. These results can be considered for further investigations aimed to identify novel natural antimicrobial compounds that could be used in aquaculture for the control of bacterial infections.     

Antibacterial effect of Lactococcus lactis subsp. lactis on Artemia franciscana nauplii and Dicentrarchus labrax larvae against the fish pathogen Vibrio anguillarum

The antibacterial effect of Lactococcus lactis subsp. lactis against the fish pathogen Vibrio anguillarum was determined in Artemia franciscana nauplii and in European sea bass (Dicentrarchus labrax) larvae fed with ten pulses of nauplii enriched with L. lactis. The evaluation of the bactericidal activity of the extracellular products of L. lactis in vitro showed inhibition of growth of Vibrio (Listonella) anguillarum and Photobacterium damselae subsp. piscicida. The incorporation of L. lactis in Artemia nauplii did not affect their survival and offered protection in a challenge with V. anguillarum, significantly increasing LD₅₀. The administration of Artemia nauplii enriched with L. lactis for 48 h to sea bass larvae for five consecutive days had no adverse effect on survival of fish. In an in vivo challenge test with V. anguillarum using sea bass larvae, fish treated with nauplii enriched with the probiotic L. lactis showed significantly (P < 0.001) increased survival rates of 81 % compared with the untreated group of challenged fish (24 %). Our results indicate that L. lactis is a probiotic suitable to be used for the prevention of vibriosis in fish larvae and can be safely administered through their live feed Artemia nauplii.     

Evaluating the protective efficacy of antigen combinations against Photobacterium damselae ssp. piscicida infections in cobia,Rachycentron canadum L.

Cobia, Rachycentron canadum L., is a very important aquatic fish that faces the risk of infection with the bacterial pathogen Photobacterium damselae ssp. piscicida, and there are few protective approaches available that use multiple antigens. In the present study, potent bivalent antigens from P. damselae ssp. piscicida showed more efficient protection than did single antigens used in isolation. In preparations of three antigens that included recombinant heat shock protein 60 (rHSP60), recombinant α‐enolase (rENOLASE) and recombinant glyceraldehyde‐3‐phosphate dehydrogenase (rGAPDH), we analysed the doses that elicited the best immune responses and found that this occurred at a total of 30 μg of antigen per fish. Subsequently, vaccination of fish with rHSP60, rENOLASE and rGAPDH achieved 46.9, 52 and 25% relative per cent survival (RPS), respectively. In addition, bivalent subunit vaccines – combination I (rHSP60 + rENOLASE), combination II (rENOLASE + rGAPDH) and combination III (rHSP60 + rGAPDH) – were administered and the RPS in these groups (65.6, 64.0 and 48.4%, respectively), was higher than that achieved with single‐antigen administration. Finally, in combination IV, the trivalent vaccine rHSP60 + rENOLASE + rGAPDH, the RPS was 1.6%. Taken together, our results suggest that combinations of two antigens may achieve a better efficiency than monovalent or trivalent antigens, and this may provide new insights into pathogen prevention strategies.     

Adhesion to sole, Solea senegalensis Kaup, mucus of microorganisms isolated from farmed fish, and their interaction with Photobacterium damselae subsp. piscicida

Abstract Most studies carried out to select microorganisms as candidate probiotics have focused on in vitro antagonism tests, such as the production of inhibitory compounds against pathogenic microorganisms. However, attachment to mucous surfaces could be another criterion to be considered when selecting potential probiotics for aquaculture. Nineteen isolates obtained from farmed Senegalese sole, Solea senegalensis Kaup, and gilthead sea bream, Sparus aurata L., have been evaluated for their capacity to adhere to skin and intestinal mucus of Senegalese sole, and their antagonistic effect against Photobacterium damselae subsp. piscicida, an important pathogen for farmed sole. The isolates from gilthead sea bream showed the highest percentage of adhesion to sole mucus, whilst the pathogenic microorganisms assayed and the isolates from sole showed, in general, a lower ability to adhere to sole mucus. The results suggest that the adhesion to fish mucus was more dependent on the isolate tested than on the host mucus. The isolates from gilthead sea bream also showed a higher antagonistic activity against P. damselae subsp. piscicida than those from Senegalese sole. Four isolates were selected, on the basis of their adhesive ability and antagonistic effect on P. damselae subsp. piscicida, to study their interactions with the pathogen in respect of adhesion to skin and intestinal mucus under exclusion, competition and displacement conditions. The results obtained show the ability of three isolates to reduce the adhesion of P. damselae subsp. piscicida to sole mucus under displacement and competition conditions. The adhesion of the pathogen to sole intestinal mucus was also significantly reduced when three isolates were assayed under exclusion conditions.     

The Efficacy of Inactivated Photobacterium damselae subsp. piscicida Combined with Levan/Alum as Vaccine against Photobacteriosis in Cobia,Rachycentron canadum

Photobacterium damselae subsp. piscicida (Phdp) is a major pathogen of cultured cobia (Rachycentron canadum), a primary target species for offshore cage culture in Taiwan. Serum antibody titers as well as efficiency and duration of protection against Phdp were evaluated following intraperitoneal administration of a candidate vaccine prepared with formalin‐inactivated whole cells in combination with levan/alum adjuvants. The results showed vaccinates delayed the disease onset and had significantly (P < 0.05) less mortality than control nonvaccinates during Days 21–105 postvaccination with highest relative percentage of survival (RPS) and antibody titer up to 81.4% and 1:614, respectively. There was a highly significant positive linear correlation between the RPS and antibody titer (R² = 0.841). Long‐lasting and significant protection against Phdp can be achieved with inactivated Phdp plus levan/alum, a potential cobia vaccine against photobacteriosis. Levan/alum complex may represent a promising adjuvant formula for the development of a Phdp vaccine.     

Review of the principal diseases affecting cultured meagre (Argyrosomus regius)

Argyrosomus regius was recently introduced in European aquaculture as a promising species for diversification and with high potential for expansion in the coming years. The reports on pathologies affecting this species are still scarce in the bibliography, however, they can severely affect production and result in major economic losses. Some few reports were made on outbreaks and mortalities associated with the presence of bacteria such as Vibrio anguillarum and Photobacterium damselae subsp. piscicida. Although no viral diseases have been recognized as affecting meagre, it is known that meagre can be an asymptomatic carrier of two genotypes of nodavirus, the striped jack nervous necrosis virus and red‐spotted grouper nervous necrosis virus. Up‐to‐date, parasites affecting meagre are included in the genera Monogenea, Nematoda and Dinoflagelate, but without major mortality outbreaks associated to this type of infections. Osteological deformities have been observed in all life stages particularly affecting the axial system in larval and early juvenile specimens, with a higher incidence in the vertebral column, being affected by vertebral fusions, lordosis and kyphosis. With this review the authors provide an overview of all the pathological and non‐pathological diseases affecting aquaculture produced meagre and provide a comprehensive overview of possible problems for the industry.     

黑棘鲷内脏结节病病原的分离、鉴定及致病性研究

2017年4月,浙江台州某海水养殖公司跑道式养殖池黑棘鲷大量发病,病鱼活力下降、食欲减退、体表溃疡,剖检可见肝脏、脾脏、肾脏肿大且有不同程度的白色结节,同时伴随大量腹水。用胰蛋白胨大豆琼脂(TSA)从典型结节病濒死黑棘鲷器官分离到革兰阴性短杆菌。分离病原菌AS15对健康黑棘鲷的致病力结果显示,AS15腹腔注射可使健康黑棘鲷发病死亡,死亡黑棘鲷可出现自然发病症状,在(24±1)°C的条件下,(25±2) g黑棘鲷的半数致死浓度(LD_(50))为6.5×10~4 CFU/尾。经API 20E鉴定,分离菌株AS15生理生化特性与类杀鱼爱德华氏菌LADL05-105和迟缓爱德华氏菌典型菌ATCC15947相似度为86.2%,与杀鱼爱德华氏菌ET~T883的相似度为82.8%;AS15的16S rDNA与杀鱼爱德华氏菌ET~T883同源性达99%,gyrB与类杀鱼爱德华氏菌LADL05-105和杀鱼爱德华氏菌ETT883同源性分别为100%和98%;16S rDNA进化树显示,AS15与ETT883、LADL05-105聚为一簇,gyrB进化树与LADL05-105、NCIM2056聚为一簇;采用4种爱德华氏菌属种特异性引物对AS15进行PCR分析,结果显示,AS15可扩增出类杀鱼爱德华氏菌的种特异性片段,不能扩增出迟缓爱德华氏菌、鲇鱼爱德华氏菌、杀鱼爱德华氏菌的种特异性片段,表明AS15属类杀鱼爱德华氏菌成员。分析了AS15的菌毛基因、sodB等毒力基因,发现AS15具有fimA、fimB、fimC、fimD等4种菌毛基因和sodB、citC、esrB、mukF、katB等毒力基因。本实验首次从黑棘鲷上检出致病性类杀鱼爱德华氏菌,该菌对黑棘鲷的发病机制和毒力机理还需进一步研究。     

Comparative pathogenicity of Vibrio spp., Photobacterium damselae ssp. damselae and five isolates of Aeromonas salmonicida ssp. achromogenes in juvenile Atlantic halibut (Hippoglossus hippoglossus)

Juvenile Atlantic halibut (~100 mg, Hippoglossus hippoglossus) were exposed to Vibrio proteolyticus, a Vibrio spp. isolate, Photobacterium damselae ssp. damselae and five different isolates of Aeromonas salmonicida ssp. achromogenes via an hour‐long bath immersion to ascertain their variation in pathogenicity to this fish species. Results were analysed using Kaplan–Meier survival analysis. Analysis of the data from challenges using A. salmonicida ssp. achromogenes revealed three survival values of zero and a spread of values from 0 to 28.43. Challenges using a Vibrio spp isolate, V. proteolyticus and P. damselae resulted in Kaplan–Meier survival estimates of 31.21, 50.41 and 57.21, respectively. As all bacterial species tested could induce juvenile halibut mortalities, they must all be considered as potential pathogens. However, the degree of pathogenicity of A. salmonicida is isolate dependent.     

Effective replacement of protein‐bound amino acids by crystalline amino acids in Senegalese sole (Solea senegalensis) juveniles

The objective of this study was to evaluate the potential of free amino acids to replace protein‐bound amino acids in diets for Solea senegalensis juveniles. For this purpose, fish with 4.26 g mean initial weight were fed during 55 days with diets containing 500 g kg^?1 protein and 100 g kg^?1 lipid, based on fish meal and fish oil as main protein and lipid sources (control diet), or diets where 20%, 35% and 50% of fish meal were replaced by crystalline amino acids, using L‐lysine HCl as lysine source. To access the efficiency of the crystalline lysine source, another diet was formulated with 35% fish meal replacement but using L‐lysine sulphate instead of L‐lysine HCl as lysine source. Overall, growth performance, feed utilization, nutrient retention, whole‐body and amino acid composition did not show significant differences among groups. In conclusion, up to 50% protein‐bound amino acids can be replaced by crystalline amino acids in diets for Senegalese sole juveniles without negative effects in fish performance. Additionally, it was shown that L‐lysine sulphate and L‐lysine‐HCl may be used interchangeably by Senegalese sole juveniles, with the potential economic benefits involved.     

The effect of dietary oxidized lipid levels on growth performance,antioxidant enzyme activities,intestinal lipid deposition and skeletogenesis in Senegalese sole (Solea senegalensis) larvae

Fish tissues, particularly rich in n‐3 PUFA, are prone to lipid peroxidation that can damage cellular membranes, cause severe lesions and subsequently incidences of disease and mortality. However, fish possess antioxidant defences, such as vitamin E (VE) and antioxidant enzymes, to protect them against oxidative damage. This study investigated the effects of an increasing gradient of oxidized dietary lipid on the survival, growth performance, skeletogenesis and antioxidant defensive processes occurring in Senegalese sole (Solea senegalensis) larvae. Four groups of fish were fed live prey enriched with experimental emulsions containing an increasing gradient of oxidized oil: non‐oxidized, NO+VE, 34.5 nmol MDA g^?1 w.w.; mildly oxidized, MO+VE, 43.1 nmol MDA g^?1 w.w.; highly oxidized, HO+VE, 63.3 nmol MDA g^?1 w.w. and highly oxidized without VE, HO‐VE, 78.8 nmol MDA g^?1 w.w. The oxidation levels increased in enriched rotifers following the oxidation gradient of the emulsions, but were not affected in enriched Artemia metanauplii. The oxidation status of Senegalese sole larvae increased during development, but this was not related to the dietary treatments. The increasing dietary oxidation levels did not affect the fatty acid profile, survival, growth performance and metamorphosis processes of sole larvae. Senegalese sole seem to activate antioxidant defence mechanisms in response to the increasing amounts of dietary peroxidized lipids, in a manner efficiently enough to prevent detection of any alterations of these physiological processes. Antioxidant systems and detoxification mechanisms appeared to occur through the consumption of dietary α‐tocopherol, the activation of the antioxidant enzymes (catalase, superoxide dismutase, glutathione S‐transferase, glutathione reductase) and the retention of oxidized fat in the intestinal enterocytes for detoxification prior to their utilization. However, fish fed the highest oxidized diet presented a reduction in bone mineralization, but lower incidence of deformities in the vertebral and caudal regions than fish fed the other diets. This study exemplifies the importance of rearing Senegalese sole larvae on non‐oxidized diets during the early larval development to avoid detrimental consequences in older fish, most notably in the process of skeletogenesis.