Turbot Larvae Research Articles

An acyl homoserine lactone-degrading microbial community improves the survival of first-feeding turbot larvae ( Scophthalmus maximus L.)

Two N-acyl homoserine lactone (AHL) degrading enrichment cultures (EC3 and EC5), originating from the microbial community of the Penaeus vannamei shrimp gut, were incorporated into first-feeding turbot larvae through addition to the rearing water and/or bio-encapsulation in rotifers, prior to their feeding to the turbot larvae. Both ECs were able to colonize the larval gut and to persist up to five days after their addition was discontinued. However, only EC5 was effective in improving turbot larvae survival under the experimental conditions, i.e. when the survival of turbot larvae was compromised through the daily addition of AHL molecules (1 mg l − 1 ). The latter treatment reduced the survival to 5.9% or 10.4% dependent on the experiment (while in the control treatment, the survival was 35% and 92.1%, respectively). Through the addition of EC5, the effect of AHL could be nullified. There was a strong negative correlation between the residual AHL concentration in the water and the larval survival on the last day. The negative effect on turbot larval survival might be caused by AHL-induced in situ production of virulence factors by uncharacterised opportunistic bacteria, while EC5 can counteract this effect. These results suggest that quorum sensing interference might become part of novel non-antibiotic based strategies to overcome high mortalities in the industrial larval production of marine fish.

Energy allocation and metabolic scope in early turbot, Scophthalmus maximus, larvae

Early stages of marine fish larvae are characterized by fast growth while having a limited aerobic scope and an immature digestive system. In order to understand this apparent paradox, the study of energy allocation is a major necessity. Components of the energy budget of turbot (Scophthalmus maximus) larvae were determined during initial development (days 4–12) and the complete energy allocation budget is presented. It was observed that food absorption efficiency increased from 32 to 51% during the studied period, and so did the energy available for growth and metabolic purposes. The relative amount of energy for maintenance decreased from 71 to 36% of energy channelled to metabolism. Gross growth efficiency increased from 20 to 26% of ingested energy, and net growth efficiency decreased from 66 to 52% of assimilated energy. Reduction of net growth efficiency is the reflex of a higher metabolic rate in older larvae, due to increased costs of activity and growth. Evidence, indicating that metabolic scope of early turbot larva is unable to accommodate simultaneously high levels of growth and activity was found. Alternative strategies to accommodate the costs of growth and activity exist in turbot larvae, and may result in a trade-off between fast growth and viability. As larvae grow, the various physiological processes described get more efficient, and the metabolic scope increases.

Genotyping and Pathogenicity of Viral Hemorrhagic Septicemia Virus from Free-Living Turbot ( Psetta maxima ) in a Turkish Coastal Area of the Black Sea

Viral hemorrhagic septicemia (VHS) is one of the most serious fish viral diseases for cultured rainbow trout (Oncorhynchus mykiss), although VHS virus (VHSV) seems to be ubiquitous among marine fishes. In the present study, VHSV isolation was performed with free-living and cultured turbot (Psetta maxima) in the Trabzon coastal area of the Black Sea to evaluate participation of VHSV in mass mortalities of seed-produced turbot larvae. VHSV was detected in 14 of 66 free-living spawners (positive ratio, 21.2%), 1 of 65 free-living immature fish (1.5%) and 7 of 40 cultured brood stock (17.5%), respectively. Based on a partial glycoprotein gene nucleotide sequence, Turkish VHSV isolates were classified into the class I-e of genotype I and were the most closely related to the GE-1.2 isolate (>98% identity), which was found >20 years ago in Georgia. Thus, it was revealed that Turkish VHSV isolates were not introduced from European countries, it could be an indigenous type of VHSV distributing in the Black Sea environment. In pathogenicity tests, the Turkish isolates did not induce mortality in turbot larvae and rainbow trout fingerlings. Mass mortalities at a rate of approximately 90% occurred in turbot larvae produced by experimental seeding, although VHSV was not detected in any dead fish. Thus, it was concluded that mass mortality in the seed-produced turbot larvae was not caused by VHSV infection.

The relationship between ultraviolet and polarized light and growth rate in the early larval stages of turbot ( Scophtalmus maximus), Atlantic cod ( Gadus morhua) and Atlantic herring ( Clupea harengus) reared in intensive culture conditions

Even small changes in light intensity and spectral composition can have significant effects on the feeding rate, survivorship and growth of marine organisms. For fishes that can perceive them, ultraviolet-A radiation (320–400 nm, UVA) and polarized (POL) light purportedly increase the visibility of prey by enhancing target contrast. Consequently, the efficiency of prey location and ingestion (and, therefore, growth) should be higher in environments rich in UVA and/or POL light. We tested this hypothesis in growth rate experiments with larvae of Atlantic cod ( Gadus morhua), turbot ( Scophthalmus maximus) and Atlantic herring ( Clupea harengus). Turbot larvae possess an UVA-sensitive retinal photoreceptor, while cod and herring larvae apparently do not. Cod, turbot and herring larvae were reared in intensive culture – for at least 18 to 35 d from first-feeding – in 45 l optically isolated matt-black tanks under four light conditions: UVA + POL; UVA + DIFFUSE; NOUVA + POL; NOUVA + DIFFUSE. All light environments were matched for photon flux. There were five replicates per light exposure treatment and larvae were sampled every 3 to 5 d for dry weight. There was no significant difference in growth for any of the larvae under any of the light treatment conditions. These results indicate that, for these species, neither UVA nor POL light significantly improves growth rate in typical intensive culture systems.

Probiotic effect in vivo of Roseobacter strain 27-4 against Vibrio (Listonella) anguillarum infections in turbot ( Scophthalmus maximus L.) larvae

The purpose of this study was to evaluate the probiotic effect of the marine bacterium Roseobacter strain 27-4 in turbot larvae infected with the pathogen Vibrio (Listonella) anguillarum. Initial trials demonstrated that cells of Roseobacter were not harmful to larvae whereas, large amounts of bacterial culture supernatant caused rapid mortality (70% at day 10 compared to 20% in the control). A similar high mortality was, however, also seen, when sterile marine broth was added to the larvae. Presumably both types of medium enhanced growth of opportunistic pathogens. In subsequent trials, both a pathogen, Vibrio anguillarum, and the probiont, Roseobacter strain 27-4, were delivered to the larvae incorporated in rotifers. Accumulated mortality of Vibrio infected larvae increased to 80–90% over 10 days, whereas, mortality in non-infected controls was significantly lower (60–70%). Feeding larvae with rotifers enriched with Roseobacter 27-4 parallel to V. anguillarum infection, brought the accumulated mortality to the level of control indicating a clear in vivo effect. Roseobacter 27-4 could be detected in larvae both by agar plating and by immunohistochemistry, being located in the gastrointestinal lumen, and apparently did not colonise the larval gut and intestinal epithelium. Plate counts decreased when enriched feed was no longer added, suggesting that the probiont, Roseobacter 27-4, should be supplied repeatedly to exert its positive effect.

Effect of dietary inulin and oligosaccharides as prebiotics for weaning turbot, Psetta maxima (Linnaeus, C. 1758)

Preliminary experiments were undertaken to investigate the effect of dietary inulin (Raftiline ST), oligofructose (Raftilose P95) and lactosucrose on the growth and intestinal bacteria of the marine carnivorous turbot, Psetta maxima. Turbot larvae were weaned on compound diets containing 2% Rafiline ST, 2% Raftilose P95 or 2% lactosucrose; 2% cellulose was the carbon source in the control group. The final mean weight of the group weaned with Raftilose P95 was significantly higher than those observed with the other diets. The bacterial load was highly variable in weaning turbot, especially with respect to the putative Vibrio spp. growing on TCBS agar which, in general, seemed to be dominant. Of the total load of bacterial isolates from turbot weaned on oligofructose, 14% consisted of a strain of Bacillus spp. This strain could use Raftilose P95 as a single source of carbon, and it might play a role in the beneficial effect of oligofructose on turbot growth, since Bacillus spp. have been documented as probiotics in fish.

A model for experimental infections with Vibrio (Listonella) anguillarum in first feeding turbot ( Scophthalmus maximus L.) larvae under hatchery conditions

Vibriosis is one of the main causes of mortality in all stages of fish. In larvae, further improvements on the control and knowledge of bacterial diseases require the development of models for experimental infections. A reproducible model for in vivo infections of first feeding turbot ( Scophthalmus maximus) larvae with the pathogen Vibrio (Listonella) anguillarum is described. Experimental challenges were carried out under hatchery conditions considering different ways of delivery of V. (Listonella) anguillarum strain 90-11-287 serotype O1 to turbot larvae: via rotifers (orally) and via water of the larval rearing tanks (bath). The effect of the supernatant of the bacteria culture was also considered and discussed. The model proposed is based on the incorporation of the bacteria into previously enriched rotifers and the delivery to the larvae during the rotifer feeding period. The effect of infections was already evident 24–72 h after the first challenged day. Final mortalities (days 8–14) in infected larvae were 56–72% with respect to unchallenged larvae. Mortalities achieved by applying the protocol of infection are reliable, reproducible and adequate for experimental purposes. The model of infection via rotifers proposed in this study is a useful tool for experimental purposes in the larval rearing of marine fish.

Vibrio splendidus biotype 1 as a cause of mortalities in hatchery-reared larval turbot, Scophthalmus maximus (L.)

To characterize bacteria associated with turbot larvae feeding on Artemia and identify pathogens causing mortalities in larvae. To identify bacteria associated with mortalities in larval turbot rearing, bacteria were isolated from homogenates of Artemia or from several batches of well-performing or poorly performing turbot larvae. Samples were plated onto marine agar and were characterized using biochemical tests and BIOLOG GN plates. Total culturable aerobic bacteria ranged from 1.9 x 10(5) to 1.8 x 10(6) CFU per larva and >96% of bacteria identified were vibrios. Almost all bacteria were haemolytic and clustered into two phenons represented by Vibrio alginolyticus and Vibrio splendidus. The bacterial flora of Artemia was almost entirely V. alginolyticus, whereas V. splendidus biotype 1 dominated the larval turbot gut flora (69/115 isolates in seven experiments) and formed four different groups based on BIOLOG GN reactions. Of 16 isolates tested for virulence towards turbot larvae, four of the 11 V. splendidus biotype 1 isolates were lethal and all belonged to the same group of V. splendidus biotype 1 isolates. In a commercial turbot hatchery, the microbial flora of the larval gut was dominated by V. splendidus biotype 1. Four of the 11 V. splendidus biotype 1 isolates caused mortalities in larval turbot and all belonged to one group of the biotype 1 strains identified. Identification of four isolates of V. splendidus that are pathogenic for turbot larvae from three separate batches of larval turbot will allow these to be compared with avirulent isolates to define how V. splendidus causes mortalities in larval turbot.

Seasonal Incidence of Autochthonous Antagonistic Roseobacter spp. and Vibrionaceae Strains in a Turbot Larva ( Scophthalmus maximus ) Rearing System

Bacteria inhibitory to fish larval pathogenic bacteria were isolated from two turbot larva rearing farms over a 1-year period. Samples were taken from the rearing site, e.g., tank walls, water, and feed for larvae, and bacteria with antagonistic activity against Vibrio anguillarum were isolated using a replica plating assay. Approximately 19,000 colonies were replica plated from marine agar plates, and 341 strains were isolated from colonies causing clearing zones in a layer of V. anguillarum. When tested in a well diffusion agar assay, 173 strains retained the antibacterial activity against V. anguillarum and Vibrio splendidus. Biochemical tests identified 132 strains as Roseobacter spp. and 31 as Vibrionaceae strains. Partial sequencing of the 16S rRNA gene of three strains confirmed the identification as Roseobacter gallaeciensis. Roseobacter spp. were especially isolated in the spring and early summer months. Subtyping of the 132 Roseobacter spp. strains by randomly amplified polymorphic DNA with two primers revealed that the strains formed a very homogeneous group. Hence, it appears that the same subtype was present at both fish farms and persisted during the 1-year survey. This indicates either a common, regular source of the subtype or the possibility that a particular subtype has established itself in some areas of the fish farm. Thirty-one antagonists were identified as Vibrio spp., and 18 of these were V. anguillarum but not serotype O1 or O2. Roseobacter spp. strains were, in particular, isolated from the larval tank walls, and it may be possible to establish an antagonistic, beneficial microflora in the rearing environment of turbot larvae and thereby limit survival of pathogenic bacteria.

Determination of Vibrio scophthalmi and its phenotypic diversity in turbot larvae.

The association of Vibrio scophthalmi with turbot larvae was assessed, by molecular methods with a species-specific probe, in the rearing stages of turbot (Scophthalmus maximus) larvae using a routine batch of production at a fish farm. The phenotypic diversity of this bacterial species was also studied to identify predominant phenotypes at successive stages of larval development. Vibrio scophthalmi was detected in all turbot larvae samples except in the sample from day 0 after hatching. The percentage of V. scophthalmi in the intestinal microbiota increased throughout larval development. Vibrio scophthalmi was also detected in live food (brine shrimps) and water from the tanks, but not in the sediment. All turbot larvae, 15-57 day old, showed several V. scophthalmi phenotypes, and a pattern of successive waves of phenotypes was observed during successive larval stages. This indicates that certain strains may colonize the intestine more efficiently and thus maintain their population for longer than other strains. Vibrio scophthalmi populations from turbots of different origin were very similar, suggesting that irrespective of geographical area, turbot populations share similar V. scophthalmi strains. Vibrio scophthalmi strain was not isolated from other cultured fish, only turbot larvae, at the same hatchery receiving water from the same supply.

Selection and Identification of Autochthonous Potential Probiotic Bacteria from Turbot Larvae (Scophthalmus maximus) Rearing Units

The purpose of this study was to select, identify and characterise bacteria as a disease control measure in the rearing of marine fish larvae (turbot, Scophthalmus maximus). Thirty-four out of 400 marine bacterial strains exhibited in vitro anti-bacterial activity against three fish larval pathogens. Two strains originated from culture collections and thirty two strains were isolated directly from turbot larvae rearing units using a pre-selection procedure to facilitate detection of antagonists. Approximately 8,500 colonies from colony-count plates were replica-plated on agar seeded with Vibrio anguillarum, and 196 of them caused zones of clearing in the V. anguillarum agar layer. Of these, 32 strains exhibited reproducible antibacterial properties in vitro when tested against the fish pathogens V. anguillarum 90-11-287, V. splendidus DMC-1 and a Pseudoalteromonas HQ. Seventeen antagonists were identified as Vibrio spp. and four of twelve tested were lethal to yolk-sac larvae. The 15 remaining strains were identified as Roseobacter spp. based on phenotypic criteria and 16S rDNA gene sequence analysis of two strains representing the two major RAPD groups. Most of the remaining 164 strains selected in the initial replica plating were identified as Vibrionaceae or Pseudoalteromonas. Roseobacter spp. were not lethal to egg yolk sac turbot larvae and in two of three trials, the mortality of larvae decreased (p > 0.001) in treatments where 10(7) cfu/ml Roseobacter sp. strain 27-4 was added, indicating a probiotic potential.

The effect of acute changes in temperature and light on the aerobic metabolism of embryos and yolk-sac larvae of turbot (Scophthalmus maximus)

The effect of acute changes of temperature and light on the rates of oxygen consumption and ammonia excretion of developing embryos and yolk-sac larvae of turbot (Scophthalmus maximus) reared at 15 °C were studied. Short-term temperature adjustments of ±2 °C gave a mean Q10of 2.6 for the rate of oxygen consumption. Neither the presence nor the absence of light significantly influenced this response to acute temperature changes, despite light causing a significantly higher rate of oxygen consumption in the yolk-sac larvae between 9 and 12 days after fertilisation. This elevated metabolic rate in the presence of light occurred after pigmentation of the eyes and was probably due to activity associated with food-searching behaviour of this visual feeder. Similarly, for most development, the presence or absence of light and acute temperature adjustments did not cause any significant shift in the relative fraction of amino acids catabolised at 15 °C. However, on day 10 after fertilisation when peak rates of oxygen consumption occurred in the yolk-sac larvae exposed to light, the significantly elevated apparent nitrogen quotients indicated that greater amounts of amino acids were utilised for catabolic substrate oxidation.

Amino acid requirements of fish larvae and post-larvae: new tools and recent findings

This paper reviews methodologies and recent findings in the study of the amino acid (AA) metabolism of fish larvae and post-larvae, in order to better understand the AA requirements. The larval indispensable AA (IAA) profile can be used as index of the IAA requirements. When turbot larvae and live food IAA profiles are compared, the profile of the latter seems to be deficient in some IAA. However, the larval IAA profile is only a rough indicator of AA requirements. A more precise estimate of the ideal dietary IAA profile implies the knowledge of the relative bioavailabilities of the individual AA, in particular, eventual differential rates of absorption and catabolism. Metabolic budgets (including unabsorbed AA, AA oxidation and AA retention) can be estimated using an in vivo method based on controlled tube-feeding of AA mixes containing a 14C-labelled AA. Results with fasted post-larval Senegal sole ( Solea senegalensis) and fasted herring ( Clupea harengus) larvae show a high retention of labelled doses of IAA (>60%) in the body, compared to catabolism as measured by liberated 14CO 2 (<25%). In contrast, dispensable AA (DAA) show a higher catabolism (>40%) and a lower retention (<57%). So, from the onset of exogenous feeding, fish larvae have high catabolic losses of AA, but use DAA preferentially to IAA as energy substrates. A new method combining the use of 13C-labelled live food and 13C-NMR spectroscopy can be used to study simultaneously the relative bioavailability of several individual AA in fish larvae. In larval gilthead seabream ( Sparus aurata) fed on rotifers, relative bioavailabilities (a combined measure of absorption efficiency and rate of catabolism) vary between AA being high for aspartate, glutamate and lysine and low for threonine. These estimates of relative biovailability of individual AA together with the IAA profiles of the larval seabream indicate that rotifers are deficient in threonine and leucine for larval seabream, threonine being the first limiting AA for protein synthesis. In order to define ideal IAA profiles for larval fish, further studies are needed on the factors affecting the relative bioavailability of IAA, such as species, age, developmental stage, temperature and the dietary nitrogen molecular form(s). Estimates of relative bioavailability of individual AA together with the IAA profile of the larval protein allow to determine the ideal dietary IAA profile for a given species.

Non-specific immune response of turbot, Scophthalmus maximus (L.), experimentally infected with a pathogenic Vibrio pelagius.

The effect of a pathogenic Vibrio pelagius, isolated during a mass mortality of turbot larvae, on the non-specific immune response of turbot, Scophthalmus maximus (L.), macrophages was studied both in vitro and in vivo. The in vitro treatment of head kidney (HK) macrophages with viable V. pelagius caused a significant inhibition of the chemiluminescence (CL) response in comparison with untreated macrophages, while incubation with heat-killed bacteria did not affect this response. In vivo, the intraperitoneal injection of V. pelagius resulted in a significant inhibition of the CL response in infected fish at days 1 and 4 post-infection compared with the control fish response. The HK macrophage nitric oxide (NO) production was enhanced by in vitro incubation with intermediate doses of viable V. pelagius (5 x 10(3) and 5 x 10(4) bacteria mL(-1)) and higher doses of the heat-killed bacteria (5 x 10(4)-5 x 10(6) bacteria mL(-1)). In both cases, the NO inhibitor N-omega -nitro-L-arginine was capable of down-regulating the specific NO induction caused by incubation with the bacterial treatments. In contrast, incubation with ECPs at higher doses caused a reduction in NO production. In vivo, a significant enhancement in NO production was also observed in macrophage supernatants at day 10 post-infection. Lysozyme concentration in the serum was also significantly increased in the experimentally infected fish at days 4 and 10 post-injection. In addition, viable V. pelagius and its ECPs significantly reduced HK macrophage viability in vitro, whereas no significant differences in viability were observed during the incubation with heat-killed bacteria. As NO production was enhanced in the experimentally infected fish, the inhibitory effect of the NO donor, S-nitroso-acetyl-penicillamine (SNAP), was tested in vitro in a cell-free assay. The results showed that growth of V. pelagius was significantly inhibited using SNAP at a high concentration (1 mM).

Isolation of a highly pathogenic Vibrio pelagius strain associated with mass mortalities of turbot, Scophthalmus maximus (L.), larvae.

A bacterial strain, characterized as Vibrio pelagius (Hq 222), was isolated from a turbot, Scophthalmus maximus (L.), larvae mass mortality in a commercial fish farm in Spain. Turbot larvae, post-larvae (0.2 g) and juveniles (5 and 15 g) were experimentally infected. The bacterium appeared to be very virulent for larvae and post-larvae, LD50 being < 5 bacteria mL(-1) for larvae 1 week post-infection and 3.9 x 10(5) bacteria mL(-1) in post-larvae at day 12 post-infection. The bacterial strain was recovered in pure culture from the internal organs of infected fish. Histological lesions in post-larvae exhibited swelling and necrosis of gill secondary lamellae, sloughing of intestinal mucosa and necrosis of haematopoietic tissue in the kidney. Vibrio pelagius (Hq 222) was able to grow in sterile sea water when incubated at room temperature or at 15 degrees C. Vibrio pelagius (Hq 222) was more adherent to the turbot cell lines TV-1 and TF than Escherichia coli. In both cell lines, the number of adhered bacteria increased with incubation time.

Three different lipid sources in formulated start-feeds for turbot (Scophthalmus maximus, L.) larvae - effect on growth and mitochondrial alteration in enterocytes

Turbot, Scophthalmus maximus, larvae were start-fed with formulated feeds containing soya phospholipids (SP), marine phospholipids (MP) or triacylglycerol (TAG). The levels of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) were the same in the MP and TAG feeds. The control group was given rotifers (R). The larvae were offered feed from day 4 post-hatch. Larvae fed formulated feed with added MP showed good initial growth and there were no significant differences in weight on day 6 between this group and the group given rotifers. Using feed with added TAG enriched with EPA and DHA gave no growth at all. Using SP as the lipid source in the feed resulted in reduced initial growth. Electron microscopical examination of enterocytes was performed on larval intestines on day 6. Larvae fed MP, TAG or rotifers had normal looking enterocytes with numerous normal looking mitochondria. In the enterocytes of larvae fed SP the mitochondria appeared swollen with a translucent matrix and fragmented cristae. Thus, SP or TAG appear not to be suitable as the sole source of lipids and/or phospholipids in start-feed for turbot larvae and the effects of MP are not solely caused by high levels of EPA and DHA.

Phospholipids in formulated start-feeds - Effect on turbot (Scophthalmus maximusL.) larval growth and mitochondrial alteration in enterocytes

Turbot Scophthalmus maximus, larvae were start-fed with formulated feeds containing marine phospholipids (MP) or soya phospholipids (SP). The experiment was performed with six experimental groups, four groups were given formulated feeds, one group was given live feed and one group was starved. Phospholipid (PL) contents of the formulated feeds were respectively 5% MP, 15% MP, 5% SP and 15% SP. Larvae were offered feed from day 3 post-hatch. There was no significant size difference on day 5 between the group fed 15% MP and the group given rotifers. Electron microscopical examination of enterocytes was performed on larval intestine on day 5. Larvae fed 5% and 15% MP and larvae fed rotifers had normal looking enterocytes with numerous normal looking mitochondria. In the enterocytes of larvae fed 5% SP and 15% SP the mitochondria appeared swollen with a translucent matrix and fragmented cristae. Thus, MP and not SP seemed suitable as a lipid and PL source for start-feeding turbot larvae.

Lipolytic activities in developing turbot larvae as influenced by diet

The development of neutral lipase and phospholipase activities was studied in larval turbot fed live prey. Activities of neutral lipase and phospholipase (activity larva−1) increased significantly between days 6 and 24 after hatching in turbot larvae. The specific activities of both enzymes (activity µg protein−1) decreased in older larvae. Feeding of a microdiet for 3 days (days 10–13) affected the lipolytic activity of neutral lipase and phospholipase negatively, compared to the larvae fed on rotifers. Since neutral lipase activities in whole larval homogenates and in the gut were significantly lower, it suggests a reduced synthesis rate and a reduced secretion of the enzyme in larvae fed the microdiet. A correlation between neutral lipase and phospholipase activities was found in larvae fed rotifers, but not in larvae fed the microdiet. This may indicate different regulating and stimulating mechanisms for these enzymes. The contribution of exogenous enzymes from ingested live prey to the total larval enzyme activity was about 6% for neutral lipase and 10% for phospholipase on day 6. The exogenous prey enzymes accounted for only 2% of the total activities in 12-day-old turbot larvae, suggesting that enzymes from prey did not contribute considerably to the digestion of lipids.

Control of Vibrio alginolyticus in Artemia culture by treatment with bacterial probiotics

In order to determine the influence of six lactic acid bacterial (LAB) strains, lactic acid and major extracellular products (ECPs) of LAB on the bacterial load of Artemia culture, two experiments were carried out. In both experiments, the dominant bacterial species were identified as Vibrio alginolyticus. The treatment with Lactobacillus brevis (1×10 8 bacteria/ml) and lactic acid (0.1 g/l) reduced the load of this bacterium in the Artemia culture water. Biochemical and morphological characteristics of the V. alginolyticus strains isolated from Artemia culture were determined. For comparative purposes, another V. alginolyticus strain isolated from diseased turbot larvae was also included. The in vitro antibacterial activity of extracellular products (ECPs) from LAB, as well as lactic acid (0.1 and 0.05 g/l), was assessed against both V. alginolyticus strains. ECPs from LAB were able to inhibit the growth of V. alginolyticus, especially those from L. brevis. In the case of lactic acid treatments, no significant inhibition of V. alginolyticus growth was observed.

Enterovibrio norvegicus gen. nov., sp. nov., isolated from the gut of turbot (Scophthalmus maximus) larvae: a new member of the family Vibrionaceae

Enterovibrio norvegicus gen. nov., sp. nov., isolated from the gut of turbot (Scophthalmus maximus) larvae: a new member of the family Vibrionaceae