Most studies of the genetic structure of Atlantic cod have focused on small geographical scales. In the present study, the genetic structure of cod sampled on spawning grounds in the North Atlantic was examined using eight microsatellite loci and the Pan I locus. A total of 954 cod was collected from nine different regions: the Baltic Sea, the North Sea, the Celtic Sea, the Irish Sea and Icelandic waters during spring 2002 and spring 2003, from Norwegian waters and the Faroe Islands (North and West spawning grounds) in spring 2003, and from Canadian waters in 1998. Temporal stability among spawning grounds was observed in Icelandic waters and the Celtic Sea, and no significant difference was observed between the samples from the Baltic Sea and between the samples from Faroese waters. F-statistics showed significant differences between most populations and a pattern of isolation-by-distance was described with microsatellite loci. The Pan I locus revealed the presence of two genetically distinguishable basins, the North-west Atlantic composed of the Icelandic and Canadian samples and the North-east Atlantic composed of all other samples. Permutation of allele sizes at each microsatellite locus among allelic states supported a mutational component to the genetic differentiation, indicating a historical origin of the observed variation. Estimation of the time of divergence was approximately 3000 generations, which places the origin of current genetic pattern of cod in the North Atlantic in the late Weichselian (Wisconsinian period), at last glacial maximum.
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The identification of North Atlantic redfish has been controversial and remains a difficult task due to overlapping of meristic and morphological characters. Here we used nine microsatellite loci to assess the level of genetic differentiation among these species and assess the resolution power of these microsatellite loci for individual assignment-based analyses. Conventional analyses as well as individual Bayesian assignment methods clearly separated the four species of North Atlantic redfish as well as the giant form of Sebastes marinus and the so-called “oceanic” and “deep-sea” types of Sebastes mentella. Locus-by-locus analyses revealed that only five microsatellite loci out of nine used could discriminate the concerned species. The advantage of the Bayesian methods relies in the individual information retrieved. It therefore gave additional information on the interrelationship among species. Indeed, we provide evidence of potential hybridization among species as well as individual misclassification based on morphological identification. We provide a powerful tool to discriminate North Atlantic redfish species, which might be useful for legal issues such as poaching, unintentional harvesting and control label.
The deepwater redfish Sebastes mentella has a wide distribution in the North Atlantic Ocean. In the Irminger Sea, there is evidence for two phenotypes (deep-sea and oceanic) of deepwater redfish. The two phenotypes have overlapping geographic distributions but differ in depth preferences. There are two hypotheses on deepwater redfish stock structure in the Irminger Sea. One suggests that mature individuals of a single stock segregate according to size and age and therefore that the phenotypes represent different life stages of the same stock. The other hypothesis suggests that there are two different stocks and that these stocks segregate mainly according to depth. Additionally, it is not clear whether the fish of the deep-sea phenotype in the Irminger Sea and those on the Icelandic continental shelf represent one stock. Analysis of genetic variability at eight allozyme markers in 1,763 deepwater redfish from 26 samples collected at different depths in the Irminger Sea and the Icelandic continental slope showed a significant difference between deep-sea and oceanic samples, suggesting the presence of two distinguishable stocks. This is supported by (1) significant heterozygote deficiency at most loci in pooled samples, (2) extensive allele frequency differences between samples classified as belonging to deep-sea and oceanic phenotypes, and (3) clustering of deepwater redfish samples of the same phenotype in a neighbor-joining dendrogram and in Bayesian analyses (STRUCTURE and the ΔK procedure for determining the number of clusters). The results indicate that deepwater redfish stock structure should be taken into account for sustainable fisheries management in the Irminger Sea and adjacent waters.
BACKGROUND: Color of muscle foods plays a major role in consumer perception of meat quality. Carbon monoxide (CO) has been successfully used for improving color of packaged meat and fish products. In this study, we wanted to investigate pre-mortem treatment of live tilapia using 100% CO for its ability to improve the color of frozen whole tilapia. We compared untreated and CO-treated whole, gutted tilapia, frozen for 2 and 4 months at − 20 °C. Frozen tilapia samples were thawed overnight at 4 °C, filleted and analyzed for their color, heme peak wavelength and CO concentration.
RESULTS: Euthanasia using CO significantly increased redness (a* value) and lightness (L* value) of tilapia white and red muscle. Frozen storage significantly (P < 0.05) decreased redness of both CO-treated and untreated tilapia. However, even after 4 months of frozen storage, a*-value of CO-treated tilapia was similar to fresh untreated tilapia fillets. Heme peak wavelengths of CO-euthanized tilapia were higher than in untreated tilapia and there was no significant (P > 0.05) decrease in heme peak wavelengths of CO-treated tilapia white and red muscle during frozen storage. The CO content of frozen euthanized tilapia fillets was significantly (P > 0.05) higher than in untreated fillets. In general, red muscle tissue of euthanized tilapia had a higher concentration of CO than white muscle.
CONCLUSION: Color stability of tilapia fillets was significantly improved by pre-mortem CO treatment. The color of CO-treated fillets was retained during frozen storage compared to untreated fillets. Hence, pre-mortem CO treatment could be used as a new method for improving color of tilapia. Copyright © 2008 Society of Chemical Industry
Carbon monoxide (CO) has been used for improving the color of muscle foods. In the current study, we compared the postmortem treatment of tilapia fillets with 100% CO and euthanasia of live tilapia with CO for their ability to stabilize the color of white and red muscle of tilapia fillets. Both postmortem CO treatment and CO euthanasia were effective in increasing the redness (a* value) and lightness (L* value) of tilapia white and red muscle. Fillets obtained from CO-euthanized tilapia showed significantly higher a* and L* values during 1 mo of frozen storage at –20 °C and subsequent thawing and storage at 4 °C for 18 d. The amount of CO present in the red and white muscles decreased during the 18 d of storage at 4 °C. There was no significant difference in the pH, drip, or thaw loss of CO-treated tilapia fillets compared to the untreated fillets.
Green, nonsulfur-like bacteria (GNSLB) and cyanobacteria form major components of microbial mats in both sulfidic and non-sulfidic hot springs and have been mainly studied in hot springs of Yellowstone National Park (YNP). These organisms synthesize specific lipid biomarkers such as wax esters and long chain polyunsaturated alkenes (GNSLB) and heptadecane (cyanobacteria). We analyzed the lipid distribution and their stable carbon isotopic composition in sulfidic Icelandic hot spring microbial mats known to contain GNSLB and cyanobacteria. Based on the lipid distribution, it seems that the GNSLB in these mats are closely related to Chloroflexus aurantiacus. The stable carbon isotopic composition of the bulk biomass and wax esters suggests mainly autotrophic growth by GNSLB in this sulfidic hot spring. However, the stable carbon isotopic composition of hentriacontatriene in the two GNSLB mats suggests an alternative carbon source for the C31:3 alkene producing GNSLB from that in YNP. The isotopic composition of cyanobacterial biomarkers in the mat most distant from the source of the hot spring seems to suggest inorganic carbon limitation for cyanobacteria, possibly because they grow underneath the GNSLB in these sulfidic hot spring inverted microbial mats.
Starch and pullulan-modifying enzymes of the α-amylase family (glycoside hydrolase family 13) have several industrial applications. To date, most of these enzymes have been derived from isolated organisms. To increase the number of members of this enzyme family, in particular of the thermophilic representatives, we have applied a consensus primer-based approach using DNA from enrichments from geothermal habitats. With this approach, we succeeded in isolating three new enzymes: a neopullulanase and two cyclodextrinases. Both cyclodextrinases displayed significant maltogenic amylase side activity, while one showed significant neopullulanase side activity. Specific motifs and domains that correlated with enzymatic activities were identified; e.g., the presence of the N domain was correlated with cyclodextrinase activity. The enzymes exhibited stability under thermophilic conditions and showed features appropriate for biotechnological applications.
The effect of filtered wood smoke (FS) processing on microbial growth in yellowfin tuna steaks was investigated. Steaks were treated for 32 h and then subjected to aerobic storage for 8 days and levels of aerobic bacteria studied. The FS treatment was compared to untreated tuna (exposed to air), 100% nitrogen (N2) (to investigate the specific effect of oxygen exclusion), 100% carbon monoxide (CO) (to investigate the effect of the CO molecule) and artificial FS (to investigate a gas with all the same gas compounds except for the smoke compounds). A study was also conducted with 21% carbon dioxide (CO2) to investigate the effect of CO2, which is found in both FS and the artificial FS. The results show that all treatments effectively (p<0.05) reduced aerobic microorganisms compared to the untreated control after 32 h, possibly due to an oxygen exclusion effect as well as to the presence of other active compounds in the gases. However, only FS, artificial FS, 100% CO and 21% CO2 treatments had a significant (p>0.05) residual antibacterial/bacteriostatic effect post-treatment. The FS treatment had the most significant residual effect (p<0.05), and this study strongly suggests this effect is due to the presence of CO2, smoke components and CO.
Survival problems are encountered at early stages of intensive fish rearing and antibiotics are widely used to remedy the situation. Probiotics may provide a potential alternative method to protect larvae from opportunistic and pathogenic bacteria and promote a balanced environment. This study was designed to search for new probiotics to target this critical period in cod rearing. Potential probionts were selected from the natural microbiota of cod aquacultural environment. The selection was based on several criteria: pathogen inhibition potential, growth characteristics, strain identification, metabolite production and adhesion to fish cell lines. Our study demonstrated that 14% of screened bacteria (n = 188) had antagonistic properties towards fish pathogens. The majority of these isolates were Gram-positive (81%), belonging to Firmicutes (69.2%) and Actinobacteria (11.5%) phyla based on 16S rRNA gene sequencing. Only 6 (3.2%) of 188 isolates could inhibit all three pathogens tested: Vibrio anguillarum, Aeromonas salmonicida subsp. achromogenes and Vibrio salmonicida. Differences observed in activity intensity and spectrum among inhibitory isolates emphasise the need to develop probiotic mixtures for efficient prophylactic methods. Comparison of growth behaviour of inhibitory isolates and pathogens at cod rearing temperatures, metabolite production and adhesion capacity were considered for final probiont selection. Four promising isolates that could be used as a mixed supplement to rearing water were identified as putative probiotic bacteria. This study emphasises the importance and potential of lactic acid bacteria in aquaculture.
A speciation technique for arsenic (As) has been applied using ion pair reverse phase-high performance liquid chromatography coupled to inductively coupled plasma mass spectrometry (RP-HPLC-ICP-MS). Six As-species (arsenite, arsenate, dimethylarsinic acid, dimethylarsinous acid, monomethylarsonic acid and monomethylarsonous acid) have been separated with isocratic elution within less than 6 minutes. A cation exchange column was used for separation of AsB, AsC, Tetra (Me4As+) and TMAsO. The As chemical form and oxidation state is highly important in respect to toxicity; therefore total As-determination is insufficient for a complete toxicological evaluation and risk assessment. Arsenic-speciation has been studied on urine samples of children from an As-affected area in the Iron Quadrangle, Brazil. DMAsV and MMAsV were the major urinary metabolites in these samples. The mean value for total As-concentration of all samples (n = 15) was 26.3 ng As mL−1 with a range of 16.1 to 55.2 ng As mL−1. TMAsO and AsC (arsenocholine) were not detected in this study. In most samples, monomethylarsonous acid [MMAsIII] was detected up to 2.0 ng As mL−1. DMAsIII was not detected at any time, most probably due to volatilisation and some oxidation to DMAsV. The chromatographic recoveries, calculated from ([sum(species) × 100]/total As in urine samples), ranged from 77.4 to 94.9%. This work also contributes to the pertinent discussion regarding the reliability of MMAsIII/DMAsIII speciation in urine.