Bacterial and parasitic pathogens in cultured common dentex, Dentex dentex L.

A bacteriological and parasitological study on cultured common dentex, Dentex dentex L., was conducted in a 2-year survey. Two different groups of fish were studied: (1) sampled only when mortalities occurred; and (2) sampled periodi-cally from 10days post-hatch until the juvenile stage. In both groups, peaks of mortalities coincided with high water temperatures. The same parasites were detected in both groups, except Ichthyophonus sp., which was identified only in the trunk kidney of fish from group 1. Two myxosporeans, Ceratomyxa sp. and Lepthotheca sp., were found in the bile and the trunk kidney, respectively. Epitheliocystis infection was also very frequent in the gills. An unidentified microsporidium, which was found in the liver, occurred very infrequently. Vibrio harveyi was dominant in samples from diseased animals (79%) and clearly associated with mortalities. It was not detected in water or larval homogenates. A high percentage (60%) of the isolates of this species were sorbitol positive. Other less frequently occurring bacteria were V. alginolyticus and Photobacterium (V.) damselae. The disease conditions found in common dentex were considered to be multifactorial in origin.     

Genetic divergence among broodstocks of Arctic charr Salvelinus alpinus in eastern Canada derived from the same founding populations

We examined the amount and distribution of molecular variation at microsatellite loci in 21 broodstocks of Arctic charr Salvelinus alpinus derived from the Fraser River, Labrador and the Nauyuk Lake, Nunavut, Canada. Our goal was to assess the amount of genetic diversity and differentiation as broodstocks are subdivided and propagated in different hatcheries and grow‐out facilities. We observed significant heterogeneity across pairs of ancestral and descendant broodstocks in the mean numbers of alleles at microsatellite loci. We detected a significant decrease in the observed heterozygosity between ancestors and descendants but the amount of decrease did not depend on either the degree of removal from the wild (number of sequential transfers) or the strain (Fraser vs. Nauyuk). Based on allele frequency distributions, there was little genetic evidence of bottlenecks during the creation of subsequent broodstock populations after the initial founding events. All broodstock samples were significantly differentiated from each other but those within the same strain were more similar to each other than to broodstocks from different strains. Broodstocks from the Nauyuk Lake broodstocks showed greater differentiation from each other than did Fraser River broodstocks, which could be attributed to differences in the number of founders.     

AFLP and microsatellites as genetic tags to identify cultured gilthead seabream escapees: data from a simulated floating cage breaking event

Genetic discrimination using DNA fingerprinting is rapidly developing for cultured stock and wild fish populations. Microsatellites and AFLPs are being widely used in aquaculture to assign fish or processed fish products, to their claimed origin, paternity or strain. In the present study, 147 AFLP and 4 microsatellite markers were used as genetic tags in gilthead seabream, Sparus auratus. Specimens from two different hatchery broodstocks (one of Atlantic and one of Mediterranean origin) and wild fishes from a natural population were fingerprinted. Putative offspring from these broodstocks were computer-generated, and the confidence in the parentage assignment of their genetic profiles to the hatchery broodstock assessed. The virtual offspring were then mixed with specimens from a natural population to simulate an accidental escape from a floating cage. The risk of false paternity inclusion was evaluated to test the ability to identify either Atlantic or Mediterranean hatchery offspring among wild fish. The method proved to be reliable, and could therefore be used to forecast the impact of fish farm escapees.     

Characterization and functional properties of digestive proteases in two sparids; gilthead seabream (Sparus aurata) and common dentex (Dentex dentex)

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.     

黄带拟鲹染色体核型特征分析

鱼类染色体核型分析在种质资源保护、遗传图谱构建、鱼类分类和育种等方面发挥着重要作用.黄带拟鲹(Pseudocaranx dentex,Bloch&Schneider,1801)是具有较高经济价值和遗传育种价值的水产资源物种,目前与该物种遗传背景相关的研究尚属空白.本研究采用热滴片法制备了黄带拟鲹鳃和鳍条组织的染色体标本...     

Changes in amino acids and essential fatty acids during early larval rearing of dentex

Samples of fertilized dentex, Dentex dentex, eggs and larvae fed enriched rotifers and Artemia according to standard hatchery procedures were analysed for free, total amino acid and fatty acid contents. Egg free amino acids (53 nmol ind-1) and total lipids (13.5 (g ind-1) levels were considerably reduced in the newly hatched larvae (6.0 nmol and 5.7 (g ind-1 respectively) while the amount of -3 PUFA (Polyunsaturated fatty acid) and 20:4-6 remained unchanged suggesting their possible role as essential fatty acids (EFA) in this species. In general, the changes in pattern of the major biochemical components during early development of dentex was similar to that outlined for other Sparidae species investigated to date. The essential amino acid profile of enriched live food did not show major imbalances when compared to that of dentex larvae. In contrast, the level of docosahexaenoic acid (22:63, DHA) and the DHA:EPA (eicosapentaenoic acid, 20:5-3) ratio in larvae given rotifers and Artemia were significantly lower relative to the corresponding values in the unfed larvae.     

Protein sparing effect of dietary lipids in common dentex (Dentex dentex): A comparative study with sea bream (Sparus aurata) and sea bass (Dicentrarchus labrax)

The common dentex (Dentex dentex) is a sparid fish which is considered a suitable candidate for Mediterranean aqua-culture. A seven-weeks feeding trial was conducted over the summer period with common dentex, sea bream (Sparus aurata) and sea bass (Dicentrarchus labrax). All three species were fed to visual satiety with two practical diets with varying crude protein and crude fat levels (55 % protein, 9 % lipids; 46 % protein, 17 % lipids). The initial body weights were 8.2, 11.6 and 17.3 g for common dentex, sea bass and sea bream, respectively. In all cases, specific growth rates were not significantly affected by dietary treatment, but they varied among species (sea bass 1.7–1.8 %; sea bream 2.1–2.3 %; common dentex 3.1–3.2 %). When comparisons between fish species were made, we observed that the increase in growth rates was linked to a decrease of the whole body fat content, as a consequence of a greater utilisation of dietary lipids as energy substrates. Furthermore, in common dentex, the 17 % lipid diet was able to improve protein retention, but this diet effect was less significant in sea bream and sea bass. In contrast to sea bream, the 17 % lipid diet did not up-regulate plasma GH levels in common dentex, which provides additional evidence for a more efficient utilisation of dietary lipids.     

Stress-related physiological responses to handling in common dentex (Dentex dentex Linnaeus, 1758)

The effects of handling on haematocrit, haemoglobin, plasma glucose, lactate and total amino acids, liver glycogen and hepatic activity of fructose 1,6‐bisphosphatase (FBPase) and alanine aminotransferase (AAT) were investigated in common dentex (Dentex dentex Linnaeus, 1758). A total of 42 fish (50‐g weight) were subjected to handling (netting and shaking in the air for 45 s). Six fish were sampled at 0, 0.5, 1, 2, 4, 8 and 12 h after handling. Six unstressed fish were also sacrificed at each time and used as controls. Handling resulted in a rise in plasma glucose and lactate levels, as well as in enhanced hepatic FBPase and AAT activities. In most cases values returned to control levels 8 h after handling. There were no significant changes in haematocrit, haemoglobin, plasma total amino acids and liver glycogen levels as a consequence of handling. The results suggest that dentex is rather tolerant to handling; apparently, sensitivity to handling is not the main factor responsible for the low survival exhibited by this species in aquaculture.     

Use of Microsatellite DNA Profiling to Identify Japanese Flounder,Paralichthys olivaceus of Hatchery Origin

Japanese flounder, Paralichthys olivaceus, is an economically important marine fish species in Asia. A suite of 18 microsatellite markers chosen from published genetic linkage maps was used to carry out parentage assignments of 188 hatchery‐reared juveniles from a small number of breeders. The probabilities of exclusion for the 18 microsatellite markers were 0.604–0.913, and the effectiveness of combined probability of exclusion reached 100% when using the eight microsatellite markers with higher Excl 1 probabilities. The cultured and wild stocks (WSs) were differentiated in a release‐recapture population based on these markers. Of the 321 recaptured offspring, 28.34% were assigned to their parental pairs in our broodstock, whereas the remaining offspring could not be traced back to a possible sire or dam. Significant reduction in genetic diversity of the cultured stock (CS) had not been found compared with that of the WS. The results suggest that CSs released into the wild will not adversely affect the genetic structure of natural populations. Our results demonstrate that these markers provide an efficient tool for parentage assignments and genetic analysis of Japanese flounder.     

荧光标记微卫星技术用于凡纳滨对虾不同家系亲权关系鉴定

应用荧光标记微卫星技术对凡纳滨对虾(Litopenaeus vannamei)家系进行亲权鉴定。挑选14个多态信息含量较高的微卫星位点,以人工选育建立的凡纳滨对虾5个全同胞家系为试验材料,采用Cervus 3.0进行亲权分析,并根据家系内个体间的遗传距离进行UPGMA聚类分析。结果表明,14个微卫星位点的平均等位基因数为6,平均多态信息含量为0.6896,平均期望杂合度为0.7309,平均观测杂合度为0.7661,第一亲本、第二亲本和双亲的累计排除率分别为0.99721733、0.99996559和0.99999997;进一步模拟分析表明,要达到亲权鉴定的要求,在双亲性别已知时至少需要5个微卫星位点,双亲性别未知时至少需要6个微卫星位点;模拟分析及试验验证所选用的14个微卫星位点最多可以鉴定1 954个已知性别的亲本或1 203个未知性别的亲本。所选用的14个微卫星标记可在生产及科研试验中用于获取凡纳滨对虾系谱信息。     

Parentage assignment in hybrid abalones (Haliotis rufescens × Haliotis discus hannai) based on microsatellite DNA markers

Parentage analysis in aquaculture determines genealogical relationships between broodstock and progeny when the parents are unknown. Thus, parentage analysis is a useful tool to establish pedigree reports in molecular‐assisted selection programs. Here, we evaluated 10 heterologous microsatellite markers for parentage assignment in abalone hybrids produced from 43 abalone broodstocks of red abalone (Haliotis rufescens) and Japanese abalone (H. discus hannai). The allele frequencies, exclusion probabilities and broodstock contributions were calculated using CERVUS, PAPA and GERUD software. The polymorphic information content (PIC) values showed that most of the microsatellite loci were highly informative (>0.7) and more than 90% of parentage assignment was possible with a minimum of 5–6 microsatellite markers. Parentage assignment for hybrid and pure‐red progeny showed a better performance than pure‐Japanese progeny. This result could be due to the high level of allele loss in the parental genotypes. In addition, results indicated that only two sires contributed over 80% and 90% of red and hybrid progenies, respectively. This study gives a new molecular tool to support marker‐assisted selection in abalone hybrids produced in Chile.     

Effects of dietary arachidonic and eicosapentaenoic acids on common dentex (Dentex dentex Linnaeus 1758) larval performance

Oily emulsions containing constant levels of total fatty acids (FAs) and varying eicosapentaenoic acid (EPA) and arachidonic acid (ARA) levels were used to enrich rotifers. Common dentex larval survival and growth were compared between groups fed different enriched live prey. Growth, survival rate, and lipid composition of larvae suggest that feeding common dentex in the first 15 days posthatching with 2.5–3% EPA, 6–8% docosahexaenoic acid (DHA), and DHA/EPA ratio of 2.0–2.5 is sufficient to fulfill their EPA requirements. Higher amounts of dietary EPA did not result in any significant improvement in growth or survival. EPA requirement during this period of larval development does not seem to be as critical as other FAs during the first 15 days of common dentex larval development, but it does not exclude its essentiality later in development. In the case of ARA, nutritional requirements are low compared to other marine finfish species, with the upper limit of this essential FA being around 2% of total FAs provided in the live prey composition.     

牙鲆家系亲权鉴定的微卫星DNA标记分析

为准确进行不同家系的亲权鉴定,筛选具有高亲本排除概率的微卫星DNA标记,从牙鲆选育基础群体中挑选性腺发育良好的雌雄亲本各10尾建立全同胞家系10个,从独立饲养的每个家系中随机选取30尾个体组成系谱结构已知的家系群体,从混合培育的子代群体中随机选取200尾个体组成系谱结构未知的混合群体。48个微卫星DNA标记选自牙鲆第二代遗传连锁图谱,且均匀分布于24个连锁群上,每个连锁群2个标记。家系群体的遗传分析结果发现,10个拥有丰富遗传多态性的微卫星DNA标记表现出高的亲本排除概率,其Excl1和Excl2的范围分别为0.655~0.719和0.792~0.837。随鉴定所用微卫星DNA标记数目的增加,累计排除概率逐步升高。当使用8个微卫星DNA标记鉴定时,累计排除概率达到100%。利用这些标记开展混合群体的亲权鉴定,显示共有13个雌雄个体参与繁殖过程,不同亲本配组产生的后代数量存在差异,亲本与后代群体之间的各项遗传学统计指标不存在明显差异。研究表明,筛选出具有高亲本排除概率的微卫星DNA标记能够有效进行牙鲆家系的亲权鉴定,可以作为今后开展家系选育与DNA分子标记联合育种的候选标记。     

Evidence of Morocco dentex (Dentex maroccanus) distribution in the NE Mediterranean and relationships with environmental factors determined by Generalized Additive Modelling

The seasonal distribution of Morocco dentex (Dentex maroccanus) was investigated in relation to ocean environmental conditions in the NE Mediterranean Sea. Data were collected during a 2‐yr period (1996–1997) of quasi‐synoptic seasonal sampling using demersal trawl surveys. The study revealed evidence for the existence of environmental relationships and temporal habitat associations of Morocco dentex. The sea‐bottom salinity, the water depth (through its interaction with bottom salinity) and the spatial location appeared to be key determinants of distribution. There was a strong consistency in the pattern and significance of the observed relationships across all seasons. The present results provided direct support for a preferential seasonal aggregation of Morocco dentex in specific geographic and bathymetric regions of the study area. In all four seasons, these favourable regions were found to be relatively stable and distinct, had the highest catch‐per‐unit‐effort index, and were located over shallower grounds (50–70 m) having bottom salinity around 39.1. The current findings also indicated that, throughout the year, the species was confined below the thermocline and avoided the deeper waters (>80 m). Morocco dentex ecological preferences for certain sea‐bottom salinities, water depth zones and hydrographic regimes were suggested to contribute to the processes governing differential settlement to preferred grounds.     

Metabolic adjustments of Dentex dentex to prolonged starvation and refeeding

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.     

Early assessment of gilthead sea bream (Sparus aurata) spawning dynamics by mini‐broodstocks

The implementation of any sustainable breeding program requires a maximization of effective size (Ne) to maintain inbreeding rate at minimum levels. However, the control of Ne remains a major challenge for those species whose reproduction in captivity is based on a spawning strategy where there is no control over the established matings. The present study aims to assess the spawning dynamic of gilthead sea bream (Sparus aurata) at different dates from two mini‐broodstocks (4 ♀ and 4 ♂). Here we report the use of a simple protocol based on the genotyping of fertilized eggs from a reduced set of microsatellite loci which provides a quick evaluation of daily spawning in terms of family structuring (number of active breeders and number and family size). According to our results, the daily spawning dynamics is characterized by a fluctuation in the number of active breeders, reaching maximum values (until 100%) during peak production phase. However, the proportion of possible mating (families) in a single daily spawning never exceeded more than 81%. Unbalanced parental contributions were highly frequent, with extreme cases involving the assignment of 50%–90% of the offspring to a single family. Therefore, the use of mini‐broodstocks and the grouping of spawning harvested at different dates are proposed as strategies to minimize the inbreeding risk by providing a more optimal pattern of family structuring (increase in the number of families obtained and a more balanced parental contributions) that entails a more conservative Ne/N ratio.     

Variations in Bacterial Community of Rearing Water and Gut of Common Dentex,Dentex dentex (Linnaeus 1758), Larvae Using Three Microalgae Management Approaches

Microorganisms present in the rearing water colonize the gut of first feeding larvae and represent the first barrier against opportunistic pathogens. The aim of the experiments presented herein was to standardize a protocol for the management of rearing water and microalgae suitable for the larval rearing of common dentex. In Experiment 1, bacteria–algae interactions were tested using a monospecific microalgal community, Tetraselmis chuii, suitable for nutritional experiments and with known antibacterial activity. In Experiment 2, the evolution of the bacterial community and larval performance (growth and survival) were monitored daily, in three conditions: (1) mature water: T. chuii was added 5 d before the rearing of common dentex larvae, (2) green water: T. chuii was added 1 d before, and (3) clear water: no T. chuii addition. The results show the influence of the presence of T. chuii on the evolution of the bacterial communities, both in terms of bacterial density and morphology, and indicate green water is the most suitable water treatment for management of larval rearing for common dentex.     

Egg quality determination based on the shape of the lipid vesicle in common dentex, Dentex dentex

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.     

Dietary intake of probiotics and maslinic acid in juvenile dentex (Dentex dentex L.): effects on growth performance, survival and liver proteolytic activities

Two feeding trials were carried out to evaluate the efficiency of probiotics and maslinic acid, on growth and survival of juvenile dentex; liver proteolytic activities were also investigated in the second trial. For experiment 1, triplicate groups were fed six diets with two probiotics (Bacillus toyoi, T, and B. cereus, E) at increasing levels (0.5, 1 and 2 g kg^?1 diet) and a control diet. Growth and feed conversion were not significantly influenced by the probiotics. The diet T1 produced the lower mortality, whereas diet E1 rendered the higher mortality. It was concluded that no significant effects on growth and survival were found following the addition of two kinds of probiotics to dentex diets. However, the diet E0.5 showed a tendency to ameliorate the growth and feed utilization of the diet. In a second trial, triplicate groups were fed four diets with increasing levels of maslinic acid (0, 20, 40 and 80 mg kg^?1 diet). Growth of fish given diets with the highest level of maslinic acid (D80) was slightly but not significantly lower than those from the other groups. Furthemore, mortality of fish fed diet D40 was the lowest. Changes in liver proteasome and endoprotease activities measured on sodium dodecyl sulphate (SDS)/gelatin gels were also detected in a dose‐dependent manner. It was concluded that a dietary maslinic acid at a level of 80 mg kg^?1 diet seems to be too high for juvenile dentex to maintain a maximal growth and survival rate.     

Reproductive biology of pink dentex Dentex gibbosus (Rafinesque) from the Adriatic Sea, Croatia

A 4‐year study (May 1997–December 2000) of the reproductive biology of pink dentex Dentex gibbosus (Rafinesque) from the Adriatic Sea revealed that this species is a rudimentary hermaphrodite. The smallest mature males and females captured were 38.70 cm in total length (T_L) and 39.80 cm in total length (T_L) respectively. The von Bertalanffy growth parameters estimated for the entire population were: L_∞=107.24, K=0.12 and t₀=−0.90. Fifty per cent of the population were sexually mature at 41.50 cm T_L, while 100% of the specimens were sexually mature at 57.00 cm T_L. Both monthly gonadosomatic index and macroscopically determined gonad stages strongly indicate that the pink dentex from the Adriatic Sea spawn partially in August, September and October. The mean value of absolute fecundity (F) was 1672 × 10⁶ eggs. The results of great fertility of the pink dentex, partial spawning and relatively late sexual maturation suggest that the pink dentex has a high potential for commercial culture.