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A. T. Correia - One of the best experts on this subject based on the ideXlab platform.
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population structure and connectivity of the european Conger eel Conger Conger across the north eastern atlantic and western mediterranean integrating molecular and otolith elemental approaches
Marine Biology, 2012Co-Authors: A. T. Correia, Ana A Ramos, Filipe Barros, Goncalo Silva, Paul A Hamer, Pedro Morais, Regina L Cunha, Rita CastilhoAbstract:Genetic variation (mtDNA) of the European Conger eel, Conger Conger, was compared across five locations in the north-eastern Atlantic (Madeira, Azores, South Portugal, North Portugal and Ireland) and one location in the western Mediterranean (Mallorca). Genetic diversity of Conger eel was high, and differentiation among regions was not significant. Additionally, comparisons of element:Ca ratios (Sr:Ca, Ba:Ca, Mn:Ca and Mg:Ca) in otolith cores (larval phase) and edges (3 months prior to capture) among the Azores, North Portugal, Madeira and Mallorca regions for 2 years indicated that variation among regions were greater for edges than cores. Therefore, while benthic Conger may display residency at regional scales, recruitment may not necessarily be derived from local spawning and larval retention. Furthermore, data from otoliths suggest a separated replenishment source for western Mediterranean and NE Atlantic stocks. The combination of genetics and otolith chemistry suggests a population model for Conger eel involving a broad-scale dispersal of larvae, with limited connectivity for benthic juvenile life stages at large spatial scales, although the existence of one or multiple spawning grounds for the species remains uncertain.
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stock discrimination of european Conger eel Conger Conger l using otolith stable isotope ratios
Fisheries Research, 2011Co-Authors: A. T. Correia, F Barros, A N SialAbstract:Abstract European Conger eel ( Conger Conger ) is a common and widely distributed fish in the NE Atlantic and Mediterranean. Although there is increasing evidence that stocks of European Conger eel are in decline, there is little published material on the population structure or management of the species. Stable isotope ratios, namely δ 18 O and δ 13 C, measured by standard mass spectrometric techniques in whole otolith samples of juvenile Conger eels sampled in April/May 2006 from NE Atlantic (Azores, Madeira and North Portugal) and Mediterranean (Mallorca) exploited stocks provided location-specific signatures. Isotopic ratios for Conger eel were similar to those reported for other marine species (δ 18 O‰, mean ± SE: 1.64 ± 0.04, 1.87 ± 0.02, 1.26 ± 0.03, 2.41 ± 0.02 and δ 13 C‰: −1.78 ± 0.08, −2.09 ± 0.07, −3.43 ± 0.15, −2.73 ± 0.12, respectively for North Portugal, Azores, Madeira and Mallorca). Relationships between isotopic ratios (δ 18 O and δ 13 C) and otolith mass were not significant. Seawater temperature could partially explain the differences in δ 18 O of otoliths among the fishery locations. The δ 18 O signatures of the Portuguese mainland coastal specimens were, however, lower than expected values, possibly as a result of the freshwater input of the Douro River located in the vicinity of this fishery area. The inter-site variation of carbon isotopic signatures was likely related to slight differences in diets or DIC of the water. The distinct isotopic signatures suggest low levels of connectivity between the fishing grounds and that Conger eels are relatively sedentary during the juvenile phase. Isotopic signatures in the otoliths of C. Conger clearly discriminated between the NE Atlantic and the Mediterranean fishery areas providing support for treatment of these fisheries as different management units.
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age growth and reproductive biology of the european Conger eel Conger Conger from the atlantic iberian waters
Fisheries Research, 2009Co-Authors: A. T. Correia, S Manso, Joao CoimbraAbstract:Abstract The European Conger eel, Conger Conger, is a fish widely distributed in the north-eastern Atlantic, being an important commercial and recreational fish species. A total of 85 juvenile Congers eels were used in this study. Seventy-three Congers were captured mainly by hook and pots in inshore waters (10–15 m depth) of the Iberian Peninsula (North Portugal and Vigo), monthly from March 1998 to March 2000. Another twelve specimens have been captured during a research cruise (R.V. “Capricornio”) in summer 1999 by trawl at depths about 400 m in south Portugal. The length and weight of the Congers eels ranged from 38 to 173 cm and 125 to 14,553 g, respectively. The observation of burnt otoliths under UV light proved to be a useful method for ageing Conger eels. Marginal increment analysis was used to validate the annual pattern in the deposition of bright zones in the otoliths. Age for the Congers ranged from 2 to 12 years. The VBF population growth curve estimates from the otoliths of the females gave results of L∞ = 265 cm, k = 0.07 and t0 = −1.20. Sex determination and gonadal development were obtained from histological analysis. All the specimens collected in the coastal shallow waters were females, either immature or in a developing stage. The ovaries contained oocytes in two main stages of development: a pre-vitellogenic stage and an early vitellogenic stage. The few males (n = 4) observed have been captured in the trawl fishery at deeper waters. The males possessed small cells spermatogonias and spermatocytes clustered in crypts in the testis scattered in a matrix of adipose tissue. The sexual steroids, 17β-oestradiol and testosterone, were measured in blood plasma samples by solid-phase radioimmunoassay. Both sexual steroids presented a high correlation with the sexual development stage in terms of maximum oocyte diameter and gonadosomatic index. This work presents for the first time, data on age, reproductive biology and endocrinology of Conger eels captured in the west coast of the Iberian Peninsula.
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evidence for genetic differentiation in the european Conger eel Conger Conger based on mitochondrial dna analysis
Fisheries Science, 2006Co-Authors: A. T. Correia, Rui Faria, P Alexandrino, Carlos Antunes, Eduardo Isidro, Joao CoimbraAbstract:The European Conger eel Conger Conger is an important marine benthic fish in the North-East Atlantic and represents a valuable fishery resource. However, little is known about its reproductive biology. In an attempt to gain a better understanding of the Conger eel population structure, mitochondrial DNA (mtDNA) sequences were examined. A region with 432 bp of the control region of the mtDNA was sequenced from 40 individuals from six different locations around the central and eastern North Atlantic Ocean. Thirty variable positions defined 28 distinct haplotypes. The average sequence difference within samples (1.3–4.2%) was comparable to those between samples (1.4–3.6%). MtDNA sequence-based statistical tests showed significant geographic differentiation between some local population samples, suggesting that the Conger eel does not comprise a single panmictic population. However, given our sample sizes, these preliminary results should be interpreted with caution and more individuals from more sites, including the Mediterranean Sea, should be analyzed in detail. The genetic variability detected in this study is an initial step to elucidate the genetic back-ground of the Conger eel population structure.
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an evaluation of the otolith characteristics of Conger Conger during metamorphosis
Journal of Fish Biology, 2006Co-Authors: A. T. Correia, Carlos Antunes, Jonathan M Wilson, Joao CoimbraAbstract:A sample of 20 metamorphosing Conger eel Conger Conger leptocephali were collected from the Minho River, Portugal, in February 1999 and their sagittal otoliths were analysed by scanning electron microscopy. Four different etching agents were applied along both sagittal and frontal sections during otolith preparation to examine the microstructural growth in this species. Otolith growth increments were visible throughout the increment countable zone using all four treatments, but a permanent peripheral diffuse zone, where the daily increments were unclear, appeared on all otoliths, preventing accurate age estimation. To understand more about the nature of the diffuse zone, otoliths of 10 other metamorphosing leptocephali reared in aquaria were marked by immersion in tetracycline hydrochloride. The distance between the fluorescent marks and otolith edge, measured over a fixed period of time, was used to estimate the otolith growth rate. The application of this technique led to an anomalously high estimated otolith growth rate, probably as a result of the capture, marking and handling stress.
Katsumi Tsukamoto - One of the best experts on this subject based on the ideXlab platform.
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water temperature manipulation can induce oocyte maturation and ovulation in the common japanese Conger Conger myriaster
Aquaculture, 2013Co-Authors: Tomoko Utoh, Noriyuki Horie, Akihiro Okamura, Yoshiaki Yamada, Satoru Tanaka, Naomi Mikawa, Hideo P Oka, Katsumi TsukamotoAbstract:Abstract To develop seed production techniques for aquaculture of the common Japanese Conger, Conger myriaster , we attempted to induce ovarian maturation and ovulation without exogenous hormone treatment and examined the changes in steroid hormones to understand the endocrine condition of the fish during their maturation process. Juveniles caught in November 2001 (20 to 30 cm in total length) were reared for 1.5 years in seawater at temperatures ranging from 10 to 20 °C before the experiments. Then, 141 randomly selected female eels (58 to 82 cm in total length) were maintained at a water temperature of 6 °C from April 2003 to March 2004. The initial GSI values (5.0 to 12.0) and oocyte diameters (300 to 400 μm) recorded in April 2003 had increased to maximum values of 30.0 and 650 μm, respectively, at the end of experiment, in March 2004. In late December 2003, 12 fish with oocytes measuring over 600 μm in diameter were selected and divided into an elevated temperature group from 6 to 10 °C and a control group of 6 °C for 43 days. The mean oocyte diameter in the elevated temperature group increased significantly, and one fish (estimated GSI, 47.0) ovulated eggs with an average diameter of 995 ± 46 μm on the 41st day at a water temperature of 10 °C, in contrast, the control group showed no significant changes in oocyte diameter, and no fish ovulated. Plasma T levels, examined via ELISA, increased with oocyte maturation, with the highest level detected at the migratory nucleus stage, and declined after ovulation. In contrast, plasma E2 was maintained at high levels during the vitellogenic stage, exhibiting the highest value after ovulation. The present study demonstrates that ovarian maturation and ovulation in the common Japanese Conger could be achieved through water temperature manipulation.
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discovery of a spawning area of the common japanese Conger Conger myriaster along the kyushu palau ridge in the western north pacific
Fisheries Science, 2012Co-Authors: Hiroaki Kurogi, Katsumi Tsukamoto, Michael J Miller, Satoshi Katayama, Noritaka Mochioka, Makoto Okazaki, Masanori Takahashi, Daisuke Ambe, Seinen ChowAbstract:The common Japanese Conger Conger myriaster is an important commercial coastal fisheries species in East Asia, but its spawning area has not been determined. A larval sampling survey was conducted in September 2008 along 136°E between 13°N and 22°N, which roughly followed the Kyushu-Palau Ridge in the western North Pacific. Twenty larval specimens were confirmed to be C. myriaster using DNA analysis. Two were newly hatched larvae (preleptocephali) 5.8 and 7.8 mm in total length (TL), which were caught at 17°N. The 5.8 mm TL larva was estimated to be 3–4 days after hatching, the youngest preleptocephalus (i.e., the earliest stage) of this species ever collected. Eighteen other leptocephali were caught at 18°N and 21°N, and these ranged from 18.6 to 40.0 mm TL. Based on these collections, we discerned that there is a spawning area of C. myriaster in the area along the Kyushu-Palau Ridge approximately 380 km south of Okinotorishima Island. Similar to the Japanese eel spawning area along the West Mariana Ridge, the Kyushu-Palau Ridge may play an important role as a landmark of the spawning area. The discovery of this offshore spawning area should lead us to a better understanding of the recruitment mechanisms of C. myriaster, and help to facilitate future international management efforts.
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offshore spawning of Conger myriaster in the western north pacific evidence for convergent migration strategies of anguilliform eels in the atlantic and pacific
Naturwissenschaften, 2011Co-Authors: Michael J Miller, Jun Aoyama, Tatsuki Yoshinaga, Tsuguo Otake, Noritaka Mochioka, Hiroaki Kurogi, Katsumi TsukamotoAbstract:The spawning area of the common Japanese Conger, Conger myriaster, had remained unknown because spawning adults or its newly hatched larvae were never collected. Using genetic identification, we determined that C. myriaster spawns far offshore in the western North Pacific, just west of the spawning area of the Japanese eel, Anguilla japonica. In June 2008, six newly hatched C. myriaster larvae, 5.6–6.9 mm, were collected at the eastern edge of where many small unidentified Conger leptocephali (7–20 mm) were collected previously. The offshore spawning location of C. myriaster is analogous to that of the American Conger eel, Conger oceanicus, and the American eel, Anguilla rostrata, in the Sargasso Sea, suggesting that convergent evolution of large-scale reproductive migration strategies in both anguillid and Conger eels has occurred in the north Atlantic and Pacific subtropical gyres. The realization that two anguillids, A. rostrata and A. japonica, and two Congers, C. oceanicus and C. myriaster, have evolved almost identical migration strategies in widely separated ocean basins suggests that natural selection for larval survival and recruitment success has resulted in long offshore spawning migrations in two phylogenetically distant taxa of anguilliform eels.
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Genetic identification of Conger myriaster leptocephali in East China Sea
Fisheries Science, 2007Co-Authors: Tao Ma, Jun Aoyama, Michael J Miller, Katsumi TsukamotoAbstract:A subsample of Conger leptocephali collected in the East China Sea (ECS) was genetically analyzed and most were found to be the larvae of Conger myriaster the most commercially important marine eel species in East Asia. However, these leptocephali (22.3–74.0 mm total length [TL]) did not have a complete row of lateral pigmentation, like the leptocephali of this species are commonly known to have when they are collected over the continental shelf or in coastal waters as they recruit. These leptocephali were in the western edge of the Kuroshio Current and the mixing zone over the shelf in the northern part of the ECS, and two smaller leptocephali (22.3, 46.5 mm TL) were collected to the south of the Ryukyu Islands. This evidence of an ontogenetic change in the presence of lateral pigmentation of C. myriaster indicates that previous efforts to determine the spawning area and recruitment patterns based on only morphological examination of Conger leptocephali in the region must be reconsidered. New research efforts based on genetic identification methods are needed to understand the spawning ecology and recruitment of this important fishery species.
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cloning and characterization of vitellogenin cdna from the common japanese Conger Conger myriaster and vitellogenin gene expression during ovarian development
Comparative Biochemistry and Physiology B, 2006Co-Authors: Naomi Mikawa, Katsumi Tsukamoto, Tomoko Utoh, Noriyuki Horie, Akihiro Okamura, Yoshiaki Yamada, Satoru Tanaka, Atsushi Akazawa, Ikuo Hirono, Takashi AokiAbstract:The major yolk protein precursor, vitellogenin (VTG) was detected in plasma from vitellogenic females and estradiol-17β (E2)-treated immature females, but not in males and immature females by Western blotting in common Japanese Conger Conger myriaster. Its molecular mass was approximately 180 kDa under denaturing and reducing conditions. The common Japanese Conger VTG cDNA was cloned from the liver of vitellogenic female. It contains 5110 nucleotides including an open reading frame that encodes 1663 amino acids. The deduced amino acid sequence of the common Japanese Conger VTG shares 80% identity with that of eel Anguilla japonica VTG-1, and 45–55%, 32–34% and 27–29% identity with the deduced amino acid sequences of other fish, amphibian and avian VTG with polyserin domain, respectively. In female common Japanese Conger, VTG gene was highly expressed in the liver of this species similar with other oviparous vertebrates. The expression levels of VTG gene in the liver increased from the oil droplet stage to the tertiary yolk globule stage and were maintained until the migratory nucleus stage.
Koji Muramoto - One of the best experts on this subject based on the ideXlab platform.
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galectins in the abdominal cavity of the Conger eel Conger myriaster participate in the cellular encapsulation of parasitic nematodes by host cells
Fish & Shellfish Immunology, 2012Co-Authors: Osamu Nakamura, Koji Muramoto, Shigeyuki Tsutsui, Tomohisa Ogawa, Mizuki Watanabe, Kazuo Ogawa, Hisao KamiyaAbstract:Congerin is a proto-type galectin distributed on the skin and mucosal epithelia of the upper digestive tract of the Japanese Conger eel Conger myriaster. It has at least 2 isotypes, namely, Congerin I and II, and plays a role in bio-defense at the body surface. In the current study, we identified both isotypes in the peritoneal fluid and peritoneal cells of C. myriaster by western blot and mass spectrometry (MS)/MS analysis. Cucullanus nematodes parasitize the abdominal cavity of C. myriaster, and immunohistochemical analyses demonstrated that Congerins can bind to both the body surface of the encapsulated nematodes and the encapsulating cells. Furthermore, adhesion of the peritoneal cells to Sepharose particles was greatly accelerated when the microspheres were coated with Congerin. Indeed, this effect was significantly hampered by the addition of lactose. These results indicate that Congerin participates in the cellular encapsulation of the Cucullanus nematode via the induction of cellular adhesion to the parasites depending on lectin-glycoside recognition.
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isolation of epidermal cells and cdna cloning of tnf decoy receptor 3 of Conger eel Conger myriaster
Fish & Shellfish Immunology, 2008Co-Authors: Shigeyuki Tsutsui, Koji Muramoto, Osamu Nakamura, Yuko Yoshino, Saho Matsui, Tasuku WatanabeAbstract:By using EDTA and a trypsin solution, we established a method for isolating the epidermal cells of the Conger eel, Conger myriaster. We then identified TNF decoy receptor (DcR) cDNA in the species from a suppression subtractive hybridization library prepared from the epidermal cells stimulated with LPS. The full-length cDNA of Conger TNF DcR (conDcR) consisted of 1479 base pairs, and the protein comprised 286 amino acid residues. Phylogenetic analysis indicated that conDcR was clustered into a DcR3 branch. ConDcR is likely to act as an important immune-regulating factor in inhibiting the apoptosis-inducing effect of TNF in the skin of Conger eel.
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the speciation of Conger eel galectins by rapid adaptive evolution
Glycoconjugate Journal, 2002Co-Authors: Tomohisa Ogawa, Hisao Kamiya, Tsuyoshi Shirai, Clara Shionyumitsuyama, Takashi Yamane, Koji MuramotoAbstract:Many cases of accelerated evolution driven by positive Darwinian selection are identified in the genes of venomous and reproductive proteins. This evolutional phenomenon might have important consequences in their gene-products' functions, such as multiple specific toxins for quick immobilization of the prey and the establishment of barriers to fertilization that might lead to speciation, and in the molecular evolution of novel genes. Recently, we analyzed the molecular evolution of two galectins isolated from the skin mucus of Conger eel (Conger myriaster), named Congerins I and II, by cDNA cloning and X-ray structural analysis, and we found that they have evolved in the rapid adaptive manner to emergence of a new structure including strand-swapping and a unique new ligand-binding site. In this review article we summarize and discuss the molecular evolution, especially the rapid adaptive evolution, and the structure-function relationships of Conger eel galectins.
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Galectin containing cells in the skin and mucosal tissues in Japanese Conger eel, Conger myriaster: an immunohistochemical study.
Developmental and Comparative Immunology, 2001Co-Authors: Osamu Nakamura, Hisao Kamiya, Tasuku Watanabe, Koji MuramotoAbstract:Abstract Congerin is a β-galactoside binding lectin (galectin) purified from the skin mucus of the Japanese Conger, Conger myriaster . To clarify its tissue distribution and productive cells, several tissue samples including skin, buccal cavity wall, tang, pharynx, gills, esophagus, stomach, intestine, liver, kidney, spleen and ovary of Conger were stained immunohistochemically using polyclonal rabbit anti-Congerin serum. In the epidermis, a number of club cells were strongly stained. Because no agglutinating activity was detected in plasma, it appears evident that Congerin is produced and secreted into mucus by those cells. In addition, Congerin-positive club cells were distributed in the mucosal epithelium lining the digestive tract preceding the stomach and in the gills. These findings suggest that Congerin participates in innate immunity on the intra- and the extra-body surface of the Conger. The putative functions of club cells in fish and their contained lectin are discussed.
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accelerated evolution in the protein coding region of galectin cdnas Congerin i and Congerin ii from skin mucus of Conger eel Conger myriaster
Bioscience Biotechnology and Biochemistry, 1999Co-Authors: Tomohisa Ogawa, Koji Muramoto, Daiji Kagawa, Chihiro Ishii, Hisao KamiyaAbstract:Two cDNAs encoding galectins named Congerins I and II from the skin mucus of Conger eel (Conger myriaster) were isolated and sequenced. Comparison of the nucleotide sequences of Congerins I and II showed that the sequence similarities of the 5′ and 3′ untranslated regions (86 and 88%, respectively) were much higher than those of the protein-coding region (73%). The numbers of nucleotide substitutions per site (K N) for the untranslated regions are smaller than the numbers of nucleotide substitutions per synonymous site (KS) for the protein coding region. Furthermore, nonsynonymous nucleotide substitutions have accelerated more frequently than synonymous nucleotide substitutions in the protein coding region (KA/KS=2.57). These results suggest that accelerated substitutions have occurred in the protein-coding regions of galectin genes to generate diverse galectins with different molecular properties. Northern blot analysis showed that both Congerins were expressed not only in the skin tissues but also in th...
Hisao Kamiya - One of the best experts on this subject based on the ideXlab platform.
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galectins in the abdominal cavity of the Conger eel Conger myriaster participate in the cellular encapsulation of parasitic nematodes by host cells
Fish & Shellfish Immunology, 2012Co-Authors: Osamu Nakamura, Koji Muramoto, Shigeyuki Tsutsui, Tomohisa Ogawa, Mizuki Watanabe, Kazuo Ogawa, Hisao KamiyaAbstract:Congerin is a proto-type galectin distributed on the skin and mucosal epithelia of the upper digestive tract of the Japanese Conger eel Conger myriaster. It has at least 2 isotypes, namely, Congerin I and II, and plays a role in bio-defense at the body surface. In the current study, we identified both isotypes in the peritoneal fluid and peritoneal cells of C. myriaster by western blot and mass spectrometry (MS)/MS analysis. Cucullanus nematodes parasitize the abdominal cavity of C. myriaster, and immunohistochemical analyses demonstrated that Congerins can bind to both the body surface of the encapsulated nematodes and the encapsulating cells. Furthermore, adhesion of the peritoneal cells to Sepharose particles was greatly accelerated when the microspheres were coated with Congerin. Indeed, this effect was significantly hampered by the addition of lactose. These results indicate that Congerin participates in the cellular encapsulation of the Cucullanus nematode via the induction of cellular adhesion to the parasites depending on lectin-glycoside recognition.
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the speciation of Conger eel galectins by rapid adaptive evolution
Glycoconjugate Journal, 2002Co-Authors: Tomohisa Ogawa, Hisao Kamiya, Tsuyoshi Shirai, Clara Shionyumitsuyama, Takashi Yamane, Koji MuramotoAbstract:Many cases of accelerated evolution driven by positive Darwinian selection are identified in the genes of venomous and reproductive proteins. This evolutional phenomenon might have important consequences in their gene-products' functions, such as multiple specific toxins for quick immobilization of the prey and the establishment of barriers to fertilization that might lead to speciation, and in the molecular evolution of novel genes. Recently, we analyzed the molecular evolution of two galectins isolated from the skin mucus of Conger eel (Conger myriaster), named Congerins I and II, by cDNA cloning and X-ray structural analysis, and we found that they have evolved in the rapid adaptive manner to emergence of a new structure including strand-swapping and a unique new ligand-binding site. In this review article we summarize and discuss the molecular evolution, especially the rapid adaptive evolution, and the structure-function relationships of Conger eel galectins.
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Galectin containing cells in the skin and mucosal tissues in Japanese Conger eel, Conger myriaster: an immunohistochemical study.
Developmental and Comparative Immunology, 2001Co-Authors: Osamu Nakamura, Hisao Kamiya, Tasuku Watanabe, Koji MuramotoAbstract:Abstract Congerin is a β-galactoside binding lectin (galectin) purified from the skin mucus of the Japanese Conger, Conger myriaster . To clarify its tissue distribution and productive cells, several tissue samples including skin, buccal cavity wall, tang, pharynx, gills, esophagus, stomach, intestine, liver, kidney, spleen and ovary of Conger were stained immunohistochemically using polyclonal rabbit anti-Congerin serum. In the epidermis, a number of club cells were strongly stained. Because no agglutinating activity was detected in plasma, it appears evident that Congerin is produced and secreted into mucus by those cells. In addition, Congerin-positive club cells were distributed in the mucosal epithelium lining the digestive tract preceding the stomach and in the gills. These findings suggest that Congerin participates in innate immunity on the intra- and the extra-body surface of the Conger. The putative functions of club cells in fish and their contained lectin are discussed.
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accelerated evolution in the protein coding region of galectin cdnas Congerin i and Congerin ii from skin mucus of Conger eel Conger myriaster
Bioscience Biotechnology and Biochemistry, 1999Co-Authors: Tomohisa Ogawa, Koji Muramoto, Daiji Kagawa, Chihiro Ishii, Hisao KamiyaAbstract:Two cDNAs encoding galectins named Congerins I and II from the skin mucus of Conger eel (Conger myriaster) were isolated and sequenced. Comparison of the nucleotide sequences of Congerins I and II showed that the sequence similarities of the 5′ and 3′ untranslated regions (86 and 88%, respectively) were much higher than those of the protein-coding region (73%). The numbers of nucleotide substitutions per site (K N) for the untranslated regions are smaller than the numbers of nucleotide substitutions per synonymous site (KS) for the protein coding region. Furthermore, nonsynonymous nucleotide substitutions have accelerated more frequently than synonymous nucleotide substitutions in the protein coding region (KA/KS=2.57). These results suggest that accelerated substitutions have occurred in the protein-coding regions of galectin genes to generate diverse galectins with different molecular properties. Northern blot analysis showed that both Congerins were expressed not only in the skin tissues but also in th...
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functional and structural characterization of multiple galectins from the skin mucus of Conger eel Conger myriaster
Comparative Biochemistry and Physiology B, 1999Co-Authors: Koji Muramoto, Daiji Kagawa, Takashi Sato, Tomohisa Ogawa, Yoshihiro Nishida, Hisao KamiyaAbstract:Abstract The complete amino acid sequence of an isogalectin, named Congerin II, isolated from the skin mucus of Conger eel, was determined by sequencing of the protein and its peptides generated by enzymatic and chemical cleavages. Congerin II consisted of 135 amino acids residues containing an acetylated N-terminus. Congerin II was found to be only 46% homologous in sequence to Congerin I which was previously determined (Muramoto K., Kamiya H., Biochem. Biophys. Acta, 1992;1116:129–136), suggesting that the galectins with diverse molecular properties are present in the skin mucus of Conger eel. However, it was confirmed by analysis of the secondary structures using circular dichroism that both Congerins I and II shared similar folds characterized by β structures. Congerins I and II showed different molecular properties such as thermostability, pH dependency for hemagglutinating activity and for binding specificity against the pyridylamino derivative of lactose. Congerin I showed more strict recognition specificity for lactose than did Congerin II. Furthermore, the effects of chemical modification on Congerins I and II were investigated in order to identify the type of amino acids involved in their different lectin activities. Modification of tyrosine and lysine residues did not affect the carbohydrate-binding activities of Congerins. However, modification of tryptophan, arginine, histidine, glutamic acid and aspartic acid residues led to considerable loss of their activities, and a different mode of binding activity was observed between modified Congerins I and II. These results suggest that multiple galectins from Conger eel with the same scaffold have different biological functions and properties.
Joao Coimbra - One of the best experts on this subject based on the ideXlab platform.
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age growth and reproductive biology of the european Conger eel Conger Conger from the atlantic iberian waters
Fisheries Research, 2009Co-Authors: A. T. Correia, S Manso, Joao CoimbraAbstract:Abstract The European Conger eel, Conger Conger, is a fish widely distributed in the north-eastern Atlantic, being an important commercial and recreational fish species. A total of 85 juvenile Congers eels were used in this study. Seventy-three Congers were captured mainly by hook and pots in inshore waters (10–15 m depth) of the Iberian Peninsula (North Portugal and Vigo), monthly from March 1998 to March 2000. Another twelve specimens have been captured during a research cruise (R.V. “Capricornio”) in summer 1999 by trawl at depths about 400 m in south Portugal. The length and weight of the Congers eels ranged from 38 to 173 cm and 125 to 14,553 g, respectively. The observation of burnt otoliths under UV light proved to be a useful method for ageing Conger eels. Marginal increment analysis was used to validate the annual pattern in the deposition of bright zones in the otoliths. Age for the Congers ranged from 2 to 12 years. The VBF population growth curve estimates from the otoliths of the females gave results of L∞ = 265 cm, k = 0.07 and t0 = −1.20. Sex determination and gonadal development were obtained from histological analysis. All the specimens collected in the coastal shallow waters were females, either immature or in a developing stage. The ovaries contained oocytes in two main stages of development: a pre-vitellogenic stage and an early vitellogenic stage. The few males (n = 4) observed have been captured in the trawl fishery at deeper waters. The males possessed small cells spermatogonias and spermatocytes clustered in crypts in the testis scattered in a matrix of adipose tissue. The sexual steroids, 17β-oestradiol and testosterone, were measured in blood plasma samples by solid-phase radioimmunoassay. Both sexual steroids presented a high correlation with the sexual development stage in terms of maximum oocyte diameter and gonadosomatic index. This work presents for the first time, data on age, reproductive biology and endocrinology of Conger eels captured in the west coast of the Iberian Peninsula.
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evidence for genetic differentiation in the european Conger eel Conger Conger based on mitochondrial dna analysis
Fisheries Science, 2006Co-Authors: A. T. Correia, Rui Faria, P Alexandrino, Carlos Antunes, Eduardo Isidro, Joao CoimbraAbstract:The European Conger eel Conger Conger is an important marine benthic fish in the North-East Atlantic and represents a valuable fishery resource. However, little is known about its reproductive biology. In an attempt to gain a better understanding of the Conger eel population structure, mitochondrial DNA (mtDNA) sequences were examined. A region with 432 bp of the control region of the mtDNA was sequenced from 40 individuals from six different locations around the central and eastern North Atlantic Ocean. Thirty variable positions defined 28 distinct haplotypes. The average sequence difference within samples (1.3–4.2%) was comparable to those between samples (1.4–3.6%). MtDNA sequence-based statistical tests showed significant geographic differentiation between some local population samples, suggesting that the Conger eel does not comprise a single panmictic population. However, given our sample sizes, these preliminary results should be interpreted with caution and more individuals from more sites, including the Mediterranean Sea, should be analyzed in detail. The genetic variability detected in this study is an initial step to elucidate the genetic back-ground of the Conger eel population structure.
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an evaluation of the otolith characteristics of Conger Conger during metamorphosis
Journal of Fish Biology, 2006Co-Authors: A. T. Correia, Carlos Antunes, Jonathan M Wilson, Joao CoimbraAbstract:A sample of 20 metamorphosing Conger eel Conger Conger leptocephali were collected from the Minho River, Portugal, in February 1999 and their sagittal otoliths were analysed by scanning electron microscopy. Four different etching agents were applied along both sagittal and frontal sections during otolith preparation to examine the microstructural growth in this species. Otolith growth increments were visible throughout the increment countable zone using all four treatments, but a permanent peripheral diffuse zone, where the daily increments were unclear, appeared on all otoliths, preventing accurate age estimation. To understand more about the nature of the diffuse zone, otoliths of 10 other metamorphosing leptocephali reared in aquaria were marked by immersion in tetracycline hydrochloride. The distance between the fluorescent marks and otolith edge, measured over a fixed period of time, was used to estimate the otolith growth rate. The application of this technique led to an anomalously high estimated otolith growth rate, probably as a result of the capture, marking and handling stress.
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age growth distribution and ecological aspects of Conger Conger leptocephali collected in the azores based on otolith analysis of premetamorphic specimens
Marine Biology, 2002Co-Authors: A. T. Correia, Carlos Antunes, Eduardo Isidro, Joao CoimbraAbstract:A total of 29 specimens of the anguillid leptocephali CongerConger were collected by the R.V. "Arquipelago", Department of Fisheries and Oceanography, University of Azores, in the waters south of the central group of the Azores Islands in October 1999. The meristic counts, morphologic features and pigmentation patterns of the leptocephali agree with the descriptions by other authors of this species. Leptocephali were found to range from 51.5 to 126.5 mm length and show a positively skewed distribution. The somatic growth rate (0.31 mm day–1), estimated from the linear regression of length on age, falls within the ranges reported by several authors for other anguilliform species. Back-calculated hatching dates from the otolith microstructure suggests a long spawning season, from January to July, with one visible annual peak, occurring in summer. The analysis of our collection data in light of the current physical oceanographic knowledge of the NE Atlantic suggests that it is unlikely that the Azorean specimens came from the Mediterranean, unless the larvae were capable of very active and oriented swimming; thus the existence of another spawning place for this species somewhere near the Azores Archipelago is probable.
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aspects of the early life history of the european Conger eel Conger Conger inferred from the otolith microstructure of metamorphic larvae
Marine Biology, 2002Co-Authors: A. T. Correia, Carlos Antunes, Joao CoimbraAbstract:The life cycle of the Conger eel (CongerConger L.) is still fairly unknown, especially its larval leptocephalus phase. The morphology, biometry and meristic characteristics of 184 metamorphosing Conger eel larvae collected from the Minho River, northern Portugal, between December 1998 and April 1999 were analysed. The total number of myomeres, the general body morphology and the pigmentation pattern of leptocephali are in agreement with the corresponding data found by other authors for this species. The sagitta microstructure of 90 specimens was viewed by scanning electron microscopy. The numbers of daily increments obtained in the otolith's countable zone were between 205 and 324. The final part of the countable zone is characterised by a sharp increase in width of the daily increments (transition zone), followed by a peripheral diffuse zone. In the diffuse zone no narrow circumscribed rings are visible, which prevents an accurate estimate of the duration of metamorphosis. The data indicates that the size variation of metamorphosing leptocephali is large, suggesting that their hatching time must be variable. Our data also show that the largest larvae, in later stages of metamorphosis, arrive first to the northern Portuguese coastal waters.