Turbot Psetta Maxima Research Articles

Molecular identification of Uronema marinum (Protozoa, Ciliophora, Scuticociliatia) in cultured turbot (Psetta maxima) larvae.

Scuticociliates are dangerous parasitic pathogens causing systemic tissue destruction and high mortality in marine fish worldwide. In this study, the first identification of Uronema marinum (Ciliophora, Scuticociliatida) from cultured turbot (Psetta maxima) larvae using mitochondrial cytochrome c oxidase 1 (cox1) gene sequence as well as species-specific primers was reported. The mean prevalence values of infected fish were calculated, and partial sequencing obtained from the mitochondrial cox1 gene region was also compared with isolates registered in the Genbank database. The sequence comparison showed 93.00% identity to U. marinum, and the parasite has also been deposited in the GenBank database. This study is the first case of U. marinum infection in Turkish marine aquaculture, contributing to the systematics and molecular epidemiology of scuticociliate in Turkey.

Flavor Quality Changes of Turbot (<i>Psetta maxima</i>) Stored at -2 and 0°C

The effect of super-chilling at -2°C compared with ice storage at 0°C on flavor quality changes of turbot (Psetta maxima) was investigated. Changes in total volatile basic nitrogen (TVB-N), sensory attributes and volatile compounds were periodically examined for 20 days. Results demonstrated that super-chilling retarded the increases of TVB-N values and maintained better sensory quality compared to the ice storage. Additionally, GC-MS analysis showed super-chilling could more effectively maintain the characteristic volatiles responsible for fresh fish flavor and reduce the contents of putrid compounds such as TMA and acetic acid.

Vaccines and immune protection of principal Mediterranean marine fish species

This review describes and summarizes the knowledge on established and experimental vaccines developed against viral and bacterial pathologies affecting the most important farmed marine finfish species present in the Mediterranean area, namely European seabass Dicentrarchus labrax, sea bream Sparus aurata, turbot Psetta maxima and meagre Argyrosomus regius. The diseases that have been recorded in seabass, sea bream and meagre are caused by bacteria Vibrio anguillarum, Photobacterium damselae, Tenacibaculum maritimum as well as by viruses such as Viral Encephalopathy and Retinopathy/Viral Nervous Necrosis and Lymphocystic disease. The main pathologies of turbot are instead bacteriosis provoked by Tenacibaculum maritimum, Aeromonas sp. and Vibrio anguillarum, and virosis by viral hemorrhagic septicaemia virus. Some vaccines have been optimized and are now regularly available for the majority of the above-mentioned pathogens. A measurable immune protection has been conferred principally against Vibrio anguillarum, Photobacterium damselae sub. piscicida and VER/VNN.

Feeding behavior and capture success of turbotPsetta maximalarvae during the transition from upright to tilted swimming position

Aquaculture production of high-quality marine fish larvae might be hampered by poor success in larval initiation of exogenous feeding or the lack of appropriate live feed in their first feeding period. The period of larval metamorphosis may further constrain the successful rearing of flatfish larvae. In order to ascertain changes in feeding during metamorphosis of flatfish, we here compared feeding behavior when larvae of turbot Psetta maxima were either swimming upright or tilted. Using video recordings, we compared the attack rate and prey capture success between flexion (12–13 days-post-hatch, stage 4b–4c) swimming predominantly in upright position and post-flexion (16–17 days-post-hatch, stage 5a–5b) larvae in tilted swimming mode. Both larval groups were fed on copepod nauplii and copepodites. Our results showed a capture success of <50% during the flexion stage, increasing to 73% in the post-flexion stage, and larvae were more successful when feeding on nauplii than when offered copepodite stages. An ontogenetic shift from intermittent to cruise swimming was observed during the metamorphosis concomitant with improved hunting skills. Thus larvae appeared to be able to successfully complete metamorphosis without compromising their feeding ability on copepod prey.

Effects of prolonged reduction of dissolved O2 concentrations on growth of turbot (Psetta maxima) juveniles.

Effects of prolonged reduction of dissolved O2 concentrations on growth of turbot (Psetta maxima) juveniles.

Physicochemical Responses and Quality Changes of Turbot (Psetta maxima) During Refrigerated Storage

The sensory, physicochemical, microbiological, and volatiles changes of postmortem turbot during 20 days of chilled storage at 4°C were studied. No significant changes were found in pH value and whiteness during the storage, while total viable counts, total volatile base nitrogen, and K-values increased significantly with storage time. The textures profile, springiness and resilience, and sensory attributes changed significantly during storage. A total of 50 volatile compounds including aldehydes, ketones, esters, alcohols, alkenes, alkanes, aromatics, amines, and others were identified in turbot muscle during storage by the solid-phase microextraction and gas chromatography–mass spectrometry methods. Among these volatile components, the relative content of some decreased significantly with time, while others increased significantly. The results suggested that hardness, springiness, resilience, sensory attributes, total volatile base nitrogen, K-value, and total viable counts combined with some volatile compounds could more perfectly reflect the quality changes of turbot during storage. The study indicated that turbot fillets stored at 4°C maintain better quality for 16 days during storage.

Depth preference in released juvenile turbot Psetta maxima

Hatchery-reared juvenile turbot Psetta maxima were tagged with Passive Integrated Transponder (PIT) tags and released at three different depths in a sandy bay in Denmark. About 2–7% of the released fish were registered daily to monitor their distribution using a tag antenna mounted on a modified beam trawl, thus avoiding actually sampling the fish. The change in distribution of the three groups was adequately represented by a two-dimensional movement model. Movement along the shore was described by a Brownian motion with group specific drift. Movement perpendicular to the shore line was described by a Cox–Ingersoll–Ross process with a group specific attraction point. All three groups exhibited similar depth preferences of 1.7m. Immediately after the release, fish were concentrated around the release points but after one day, fish had moved to the preferred depth and subsequently maintained their position at this depth. Farmed turbot exhibited strong site fidelity and an innate behaviour for selecting a preferred depth.

Uptake Kinetics, Bioconcentration and Debromination of BDE-47 in Juvenile Marine Fish Psetta maxima

Polybrominated diphenyl ethers (PBDEs) are a class of global flame retardants whose residues have markedly increased in fish and human tissues during the last decade. They belong to persistent and toxic contaminants which need more attention and toxicological study as their degradation in the environment is not well understood. This study characterizes 2,2′,4,4′-tetrabromodiphenyl ether (BDE-47) bioconcentration, elimination and biotransformation in juvenile turbot Psetta maxima, in order to evaluate the risk of its bioaccumulation in the marine environment. During this study, juvenile turbot were exposed to environmentally relevant BDE-47 concentrations from 0.001 to 1 μg/L for 16 days via aqueous exposure. This study found that juvenile turbot bioconcentrated and biotransformed BDE-47. There was no difference in standard length or weight between control and exposed fish. Uptake and elimination of BDE-47 by the turbot during exposure were examined in controlled laboratory experiments. Bioconcentration of BDE-47 was similar in fish from all treatment groups. Bioconcentration was rapid and increased with exposure time, since the bioconcentration factor (BCF) was higher. However, elimination was slower in comparison and low elimination was detected after 10 days in clean water. BDE-47 concentration in water influences the BCF. Half-life ranged between 37 and 108 days and theoretical times t 90 could range from 120 to 358 days. The present study demonstrates a stepwise debromination of BDE-47 to BDE-28.

Seasonal distribution and migration pattern of the turbot (Psetta maxima Linnaeus, 1758) in the eastern Black Sea, Republic of Turkey

Seasonal distribution and migration pattern of the turbot (Psetta maxima Linnaeus, 1758) in the eastern Black Sea, Republic of Turkey

Cryptic Behaviour of Juvenile Turbot &amp;lt;i&amp;gt;Psetta maxima&amp;lt;/i&amp;gt; L. and European Flounder &amp;lt;i&amp;gt;Platichthys flesus&amp;lt;/i&amp;gt; L.

The aim of this study was to examine the burying behaviour of hatchery-reared European flounder Platichthys flesus and turbot Psetta maxima, and whether conditioning on a sandy substrate would improve burying efficiency. Both species buried shortly after release on a sandy substrate. However, the study revealed interspecies differences; the flounder buried immediately after release, while the turbot buried gradually. No significant difference in burying efficiency was observed between na&iumlve and conditioned flounder and turbot. An effect of size on burial efficiency was observed for both flounder and turbot with a tendency for larger fish to bury more efficiently than smaller fish, despite previous conditioning. Size at settlement was found to be >2 cm for flounder and >3 cm for turbot.

Isolation of betanodavirus from farmed turbot Psetta maxima showing no signs of viral encephalopathy and retinopathy

The isolation of a betanodavirus strain from juvenile turbot showing unspecific symptoms and very low mortality is reported. The presence of an IPNV-type virus was also revealed in the fish tissues, but only after nested-PCR, suggesting a very low viral load. In addition, different Vibrio species were isolated from some of the individuals. Both viral RNAs were sequenced and phylogenetic analysis indicated that the strain showed 99% identity with the RGNNV genotype. Experimental infections (via immersion and intraperitoneal route) were conducted in order to determine the susceptibility of turbot juveniles (2 and 5g) to the NNV isolate at 15 and 18°C (range of turbot rearing temperatures in our area). The results obtained indicated that although the viral isolate was able to replicate in the turbot tissues, it did not induce clinical disease in this fish species. These findings suggest that the existence of a reservoir of NNV-RGNNV type in wild fish in the area represents a low risk for the turbot farming industry.

Analysis of the morphogenesis and cell proliferation in the retina of a pleuronectiform fish, the turbot psetta maxima (Pleuronectiformes: Teleostei)

The morphogenesis and cell proliferation in the retina of turbot (Psetta maxima, Pleuronectiformes: Teleostei) from embryo through metamorphosis have been examined by using proliferating cell nuclear antigen (PCNA)-immunohistochemistry and general histological procedures. In the embryonic retina, cell proliferation and spatial cell reorganization form the anlage of the pigment epithelium and neural retina. Neurogenesis begins around hatching in the temporal retina, dorsal to the optic nerve exit, and then a wave of cell differentiation spreads to the nasal retina to yield a laminated retina by the end of the prolarval turbot stage. Germinal zones in the differentiated retina persist as a rim at the retinal margin, as well as surrounding the optic fissure in premetamorphic and metamorphic turbot larvae. In these zones, progenitor cells with different morphologies show a similar spatial arrangement, which suggests that they have a similar retinogenic potential. During metamorphosis, asymmetric proliferative activity in turbot germinal zones is associated with a marked expansion of the retinal tissue. Scattered stem cells in the laminated retina, related to the lineage of rod photoreceptors, were also observed both in large premetamorphic larvae and metamorphic turbots. The proliferative activity of these cells increases considerably during metamorphosis, when rod photoreceptors become morphologically differentiated.

New Contributions to the Study of the Enteroendocrine System in Turbot (Psetta maxima) Following Infection with Enteromyxum scophthalmi

New Contributions to the Study of the Enteroendocrine System in Turbot (Psetta maxima) Following Infection with Enteromyxum scophthalmi

Effects of high hydrostatic pressure on selected biomarkers in turbot (Psetta maxima) in short term experiments

Effects of high hydrostatic pressure on selected biomarkers in turbot (Psetta maxima) in short term experiments

Toxicity of three selected pesticides (Alachlor, Atrazine and Diuron) to the marine fish (turbot Psetta maxima)

The present study aimed to evaluate acute toxicity tests for three selected herbicides: Alachlor, Atrazine and Diuron using turbot flatfish. Larvae were more sensitive than turbot embryos to all pesticides. Median lethal concentrations of the selected pesticides during a 48 h and 96 h exposure for turbot embryos and larvae were, respectively: alachlor, 2177 and 2233; diuron, 10076 and 7826 and atrazine, 11873 and 9957 μg/L. On the basis of the obtained acute toxicity data, all compounds were included among substances highly toxic to fish, in the following order: alachlor> atrazine> diuron. At higher concentrations, pesticides caused a significant increase in embryo mortality. Surviving organisms suffered a significant decrease in hatching success, malformations (embryos), pericardial oedema and skeletal deformation (larvae). All herbicides appear to be teratogenic to the turbot early life stage. Furthermore, the three selected pesticides differed in their toxicity to the fish. Keywords: Turbot, early life stage, acute toxicity, sublethal effects, herbicides

Virulence factors of Aeromonas salmonicida subsp. salmonicida strains associated with infections in turbot Psetta maxima

Virulence factors for Aeromonas salmonicida subsp. salmonicida (ASS) strains isolated from cultured turbot Psetta maxima L. are unknown with regard to this host. The presence of virulence genes associated with different stages of ASS infection in salmonids (vapA, tapA, fla, ascV, ascC, aexT, satA and aspA) was analysed using a polymerase chain reaction (PCR) technique in ASS strains isolated from turbot. Other ASS strains isolated from salmonids and environmental A. salmonicida (AS) strains were included for comparison. The presence of the genes was evaluated with respect to ASS virulence in turbot based on intraperitoneal and bath challenges. The genetic profile, including all of the genes studied, that was linked to virulent behaviour after intraperitoneal challenge was significantly more frequent in strains isolated from turbot than in those from salmonids or the environment. The data prove that it is not possible to predict the virulence of ASS in turbot based only on the presence of all genes tested. Moreover, the combined PCR results of vapA, aexT, ascV and ascC were useful for separating most of the ASS from environmental A. salmonicida strains. An association between virulence or genetic profile and the geographical or facility origin of the strains was not found.

Colonization of turbot tissues by virulent and ­avirulent Aeromonas salmonicida subsp. ­salmonicida strains during infection

Preventing disease outbreaks in cultured turbot Psetta maxima L. caused by Aeromonas salmonicida subsp. salmonicida (ASS) requires a better understanding of how this pathogen colonizes its host. Distribution of 1 virulent and 2 avirulent ASS strains in turbot tissues was investigated during early and late stages of infection following an immersion challenge. To track bacteria within the turbot, the ASS strains were tagged with green fluorescent protein (GFP). Both virulent and avirulent strains colonized the epidermal mucus, gills, and intestine within the first 12 h post challenge, suggesting that these sites may serve as points of entry into turbot. Although the avirulent strains colonized these initial sites in the turbot tissues, they were rarely found in the internal organs and were cleared from the host 4 d post challenge. In contrast, the virulent ASS strain was found in the liver and kidney as early as 12 h post challenge and was found in the muscle tissue at very late stages of infection. The virulent strain persisted in all tested host tissues until death occurred 7 d post challenge, suggesting that ASS must colonize and survive within the turbot tissues for an infection to result in death of the fish. Comparisons of the distribution profiles of both virulent and avirulent strains during early and late stages of an infection in turbot has provided important information on the route and persistence of an ASS infection in this host.

Early ontogeny of the Atlantic halibut Hippoglossus hippoglossus head

An ontogenetic sequence of Atlantic halibut Hippoglossus hippoglossus larvae, reared in intensive culture conditions, was cleared and stained and histologically processed to determine normal cranial chondrification for specimens ranging from 0 to 41 days post-hatch (dph). Twenty-six cranial cartilaginous structures were described, at daily intervals post-hatch. The ontogenetic trajectory, composed of alternating steps and thresholds, was interpreted as saltatory. In comparison with other flatfishes, H. hippoglossus exhibits delayed onset of chondrification. From 9 dph onwards, the ontogenetic trajectory resembles more than that of the turbot Psetta maxima than that of the common sole Solea solea or the summer flounder Paralichthys dentatus and winter flounder Pseudopleuronectes americanus. Hippoglossus hippoglossus with the gaping-jaw malformation, common in intensively cultured individuals of this species, were examined histologically. The reason larvae cannot close their mouth, as their yolk-sac resorbs, seems to be related to the fusion of the interhyal to the hyosymplectic and ceratohyal with which it is normally articulated.

Susceptibility of juvenile sole Solea senegalensis to marine isolates of viral haemorrhagic septicaemia virus from wild and farmed fish

The susceptibility of sole Solea senegalensis to infection with 3 viral haemorrhagic septicaemia virus (VHSV) strains obtained from wild Greenland halibut Reinhardtius hippoglossoides and farmed turbot Psetta maxima was demonstrated. Fish were infected by an intraperitoneal (i.p.), immersion or cohabitational route, and maintained at 16 degrees C. Infection trials showed that VHSV isolates were pathogenic for sole fingerlings by i.p. injection and waterborne exposure causing moderate levels of mortality (10 to 55%). In addition, the mortality observed in fish cohabitating with i.p.-infected sole confirms horizontal transmission of the virus. However, the low rates of mortality registered in this challenge suggest that there is a low dissemination of virus by the i.p.-infected sole, which results in lower secondary challenge of the cohabitating fish. External signs of disease included haemorrhaging of the ventral area and ascitic fluid in the body cavity. Dead fish were tested for VHSV by both cell culture and RT-PCR assay, using pools of kidney and spleen from 10 individuals. Virus was recovered from most of the pools composed of dead fish. The results obtained in this study not only demonstrate the susceptibility of sole to the VHSV strains employed but also indicate that wild VHSV marine isolates represent a potential risk for sole aquaculture.

Variation in fin ray counts of 0-group turbot ( Psetta maxima) and brill ( Scophthalmus rhombus) on the west coast of Ireland: 2006–2009

Recently settled turbot Psetta maxima and brill Scophthalmus rhombus are difficult to distinguish, as they are almost identical in appearance and lack the diagnostic adult characteristics. Fin ray counts, which can be used as an aid in the identification of flatfish juveniles, are reported to show some overlap between turbot and brill. 0-group flatfish were collected from sandy beaches along the west coast of Ireland by beach seining in 2009. When counted and plotted, the dorsal and anal fin ray counts clearly separated the specimens into two groups. The two groups were assumed to be brill and turbot on the basis of literature data, suggesting higher dorsal and anal fin ray counts occur in brill. This confirmed that fin ray counts can probably be used as a diagnostic tool in these 0-group flatfish from west of Ireland waters. Additionally, temporal and spatial variability in fin ray counts was also revealed in the present study, emphasizing that regional difference need to be taken into account when using this diagnostic method.