Activity patterns of juvenile Atlantic cod (Gadus morhua) in Buckley Cove,Newfoundland

We monitored swimming speed of 2–3 year-old juvenile Atlantic cod (Gadus morhua) from August to December 1999, using a 2-D location finding acoustic telemetry system in a coastal area of Newfoundland, Canada. We concurrently monitored the locations of 22–41 individuals by triangulation using a fixed hydrophone array. We estimated average swimming speeds at intervals of 60–120 s and compared them over a 1 to 17 °C thermal range, three diel periods, and five substrates (sand, gravel, sand-sparse boulder, boulder, and kelp). However, cod did not exhibit a change in swimming speed over the temperature range studied. Increased activity and foraging rates (expressed as swimming speeds) were expected to increase at elevated temperatures due to increased metabolic demands. Activity did vary significantly with diel cycle and substrate. Swimming speeds were significantly lower at night during September and October. Results for August and November were inconclusive, while swimming speed was significantly lower during the day in December. We observed significantly reduced average swimming speeds in structurally complex substrates (e.g. rock, cobble and kelp) in September and October. Our results suggest that activity of juvenile cod in the wild does not vary with temperature as predicted from studies in the laboratory. Instead, activity varied with diel cycles and structural complexity, variables that influence an individual's ability to forage and seek refuge, potentially altering individual fitness.     

Cross-shoal variability in the feeding habits of migrating Atlantic cod (Gadus morhua)

Prey intake and selection were related to within-shoal position for Atlantic cod (Gadus morhua) engaged in annual migration across the Newfoundland shelf in the northwest Atlantic. Comparisons made among fish occupying five regions from the front to rear of a large (>10 km across) migrating shoal indicated that leading fish, or scouts, were larger, ate more food by weight, and had a more varied diet than did fish at other positions. Also, scouts consumed more preferred prey types (fish and pelagic invertebrates) than did fish at other positions. In contrast, trailing fish consumed few fish prey but a larger proportion of benthic invertebrates. Our results are the first to document systematic heterogeneous feeding success among members of a free-ranging and migrating fish shoal in the open ocean.     

Expression of the oligopeptide transporter, PepT1, in larval Atlantic cod (Gadus morhua)

The intestinal absorption of di- and tri-peptides generally occurs via the oligopeptide transporter, PepT1. This study evaluates the expression of PepT1 in larval Atlantic cod (Gadus morhua) during the three weeks following the onset of exogenous feeding. Larval Atlantic cod were fed either wild captured zooplankton or enriched rotifers. cDNA was prepared from whole cod larvae preceding first feeding and at 1000 each Tuesday and Thursday for the following three weeks. Spatial and temporal expression patterns of PepT1 mRNA were compared between fish consuming the two prey types using in situ hybridization and quantitative real-time PCR. Results indicated that PepT1 mRNA was expressed prior to the onset of exogenous feeding. In addition, PepT1 was expressed throughout the digestive system except the esophagus and sphincter regions. Expression slightly increased following first-feeding and continued to increase throughout the study for larvae feeding on both prey types. When comparing PepT1 expression in larvae larger than 0.15-mg dry mass with expression levels in larvae prior to feeding, no differences were detected for larvae fed rotifers, but the larvae fed zooplankton had significantly greater PepT1 expression at the larger size. In addition, PepT1 expression in the zooplankton fed larvae larger than 0.15-mg dry mass had significantly greater expression than rotifer fed larvae of a similar weight. Switching prey types did not affect PepT1 expression. These results indicate that Atlantic cod PepT1 expression was slightly different relative to dietary treatment during the three weeks following first-feeding. In addition, PepT1 may play an important role in the larval nutrition since it is widely expressed in the digestive tract.     

Development of twenty sequence-tagged microsatellites for the Atlantic cod (Gadus morhua L.)

Fifty-four primer pairs were designed for expressed sequence tag (EST) sequences containing perfect di- and tri-nucleotide motifs and characterised in 96 unrelated fish. Twenty markers were successfully amplified with number of alleles from 2 to 10 per locus and observed and expected heterozygosity ranging from 0.01 to 0.56 and 0.03 to 0.70, respectively. Loci Gmo-C213, Gmo-C246 and Gmo-C247 deviated from Hardy–Weinberg equilibrium. Genetic linkage disequilibrium analysis between all pairs of the loci showed significant departure from the null hypothesis between loci Gmo-C213 and Gmo-C222, Gmo-C233 and Gmo-C229, C223 and Gmo-C236 and C229 and Gmo-C236. The gene identity was determined at 10 of the loci, confirming the associated microsatellites as Type I markers. These microsatellite markers provide useful tools for studies of population genetics, reproductive ecology and constructing linkage maps of Atlantic cod.     

New polymorphic di-nucleotide microsatellite markers for Atlantic cod (Gadus morhua L.)

Twenty three polymorphic microsatellite markers were developed from approximately 2,300 expressed sequence tags (ESTs) of Atlantic cod (Gadus morhua L.). Seventy two primer pairs were designed for EST sequences containing perfect di-nucleotide motifs and characterised in 96 unrelated fish. Twenty three markers were successfully amplified with number of alleles from 2 to 18 per locus and observed and expected heterozygosity ranging from 0.03 to 1.00 and 0.04 to 0.90, respectively. Loci Gmo-C280, Gmo-C283, Gmo-C290 and Gmo-C293 deviated from Hardy–Weinberg equilibrium. Genetic linkage disequilibrium analysis between all pairs of the loci showed significant departure from the null hypothesis between loci Gmo-C267 and Gmo-C269 and Gmo-C262 and Gmo-C291. The gene identity was determined at three of the loci, confirming the associated microsatellites as Type I markers. These microsatellite markers provide useful tools for studies of population genetics, reproductive ecology and constructing linkage maps of Atlantic cod.     

Chum salmon (Oncorhynchus keta) stanniocalcin inhibitis in vitro intestinal calcium uptake in Atlantic cod (Gadus morhua)

Summary Chum salmon (Oncorhynchus keta) stanniocalcin was purified, partially identified and tested for bioactivity in an assay on the intestinal calcium uptake in a marine teleost (Gadus morhua). Basic ethanol extraction, ion exchange chromatography, gel filtration and reverse-phase high-performance liquid chromatography resulted in the isolation of a homogenous glycoprotein that appears as a 46-kDa product under non-reducing conditions and as a 23-kDa product under reducing conditions after sodium dodecylsulphate-polyacrylamide gel electrophoresis. The glycoprotein is likely to be a homodimer composed of two subunits of 23 kDa each. Further characterization indicates homology to Australian eel, sockeye salmon, coho salmon and rainbow trout stanniocalcin, and the glycoprotein is thus concluded to be stanniocalcin. Stanniocalcin-like immunoreactivity was demonstrated in the corpuscles of Stannius of the Atlantic cod, with a specific antiserum raised against purified chum salmon stanniocalcin. The physiological importance and the biological activity of chum salmon stanniocalcin was tested by evaluating its effect on intestinal calcium uptake by the Atlantic cod in vitro. The intestine was perfused, both vascularly and through the intestinal lumen, and the calcium mucosa-to-serosa flux was measured using ⁴⁵Ca²⁺ as a tracer. Stanniocalcin decreased the intestinal calcium uptake in a dose-related manner by 13.5% and 22.4% at doses of 2.2 and 10.9 nM stanniocalcin, respectively. The results establish the intestine as a target organ for stanniocalcin in marine teleosts.Abbreviations BIS balanced intestinal solution - CS corpuscles of Stannius - dpm disintegrations per minute - FW freshwater - J _in ^Ca influx of calcium across the intestinal mucosa - MW molecular weight - NRS normal rabbit serum - PBS phosphate buffered saline - PBST phosphate buffered saline containing 0.05% Tween-20 - PITC phenyl isothiocyanate - rp-HPLC reverse phase - SW seawater - STC phenyl isothiocyanate - rp-HPLC reverse phase - SW seawater - STC stanniocalcin - TFA Trifluoroacetic acid - Tris Tris(hydroxymethyl) aminomethan - V volume per fraction     

Pro-oxidant and antioxidant processes in gas gland and other tissues of cod (Gadus morhua)

Partial reduction of molecular oxygen produces reactive oxyradicals, including the superoxide anion radical (O _- ² ) and hydroxyl radical (·OH). The gas gland functions under hyperoxic and acidic conditions and therefore is likely to be subjected to enhanced oxidative stress. Aspects of pro- and antioxidant processes in gas gland were compared with other tissues likely to be subject to differing degrees of oxyradical production, viz. liver (site of chemically-mediated oxyradical production), gills and skeletal muscle. Antioxidant enzyme activities (superoxide dismutase, catalase, selenium-dependent and total glutathione peroxidase) per g wet weight were highest in liver and lowest in muscle. Catalase and glutathione peroxidase activies per g wet weight were higher in gills than in gas gland, whereas the reverse was seen for superoxide dismutase. Cytosolic superoxide dismutase activities per mg protein were two- and nine-fold higher in gas gland than in liver and gills. The pH characteristics of the antioxidant enzymes were generally similar in all the tissues. Glutathione, vitamin E and unsaturated (peroxidizable) lipid levels were generally highest in liver followed by gas gland. Lipid peroxidation (malonaldehyde equivalents) was evident in all tissues except gas gland. Hydrogen peroxide and O _- ² were involved in the NAD(P)H-dependent ferric/EDTA-mediated formation of ·OH (as measured by 2-keto-4-methiolbutyrate oxidation) by mitochondrial and postmitochondrial fractions of gas gland. Tissue maximal potentials for ·OH production paralled superoxide dismutase but not catalase or glutathione peroxidase activities. Overall, the results confirm the presence of effective antioxidant defences in gas gland and support previous workers' contentions of a central role for superoxide dismutase in this process.Abbreviations EDTA di-sodium ethylenediaminetetra-acetic acid - G-6-P glucose-6-phosphate - GPX total glutathione peroxidase - GSH reduced glutathione - GSSG oxidised glutathione - GST glutathion-S-transferase - HPLC high performance liquid chromatography - KMBA 2-keto-4-methiolbutyric acid - MOPS 3-[N-morpholino] propane-sulphonic acid - PMS postmitochondrial supernatant - Se-GPX selenium-dependent glutathion peroxidase - SOD superoxide dismutase - TCA trichloroacetic acid     

Identification and characterisation of nine new gene-associated microsatellite markers for Atlantic cod (<Emphasis Type="Italic">Gadus morhua</Emphasis> L.)

Nine polymorphic microsatellite markers were identified by screening of 2464 ESTs derived from a cDNA library of Atlantic cod (Gadus morhua L.). About 35 novel microsatellite loci were selected and characterised in 96 individual cod. Nine markers were successfully amplified with number of alleles from 3 to 18 per locus and the average heterozygosity was 0.57 in the panel examined (range 0.29–0.86). All loci followed the Hardy–Weinberg expectation and no significant linkage disequilibrium was found in a test including all pairwise combinations. The gene identity was determined at four of the loci, confirming the associated microsatellites as Type I markers.     

Structural studies of the O-antigenic oligosaccharide from Vibrio salmonicida strain C2 isolated from Atlantic cod, Gadus morhua L

We report the chemical structure of the oligosaccharide part of Vibrio salmonicida lipopolysaccharide serotype C2, isolated from Atlantic cod (Gadus morhua L.). The structure was established by NMR spectroscopy and mass spectrometry. It is concluded that the oligosaccharide has the following structure in which L-alpha-D-Hepp is L-glycero-alpha-D-manno-heptopyranose, D-alpha-D-Hepp is D-glycero-alpha-D-manno-heptopyranose, alpha-NonA is 5-acetamidino-7-acetamido-3,5,7,9-tetradeoxy-L-glycero-alpha-D-galacto-nonulosonic acid, and PEA is phosphoethanolamine. [chemical structure: see text]     

Autonomic nervous control of blood pressure and heart rate during hypoxia in the cod,Gadus morhua

Summary The autonomic nervous and possible adrenergic humoral control of blood pressure and heart rate during hypoxia was investigated in Atlantic cod. The oxygen tension in the water was reduced to 4.0–5.3 kPa (i.e.. P_wO₂=30–40 mmHg), and the fish responded with an immediate increase in ventral and dorsal aortic blood pressure (P _va P _da), as well as a slowly developing bradycardia. The plasma concentrations of circulating catecholamines increased during hypoxia with a peak in the plasma level of noradrenaline occurring before the peak for adrenaline. Bretylium was used as a chemical tool to differentiate between neuronal and humoral adrenergic control of blood pressure and heart rate (f _H) during hypoxia. The increase in P _va and P _da in response to hypoxia was strongly reduced in bretylium-treated cod, which suggests that adrenergic nerves are responsible for hypoxic hypertension. In addition, a small contribution by circulating catecholamines to the adrenergic tonus affecting P _va during hypoxia was suggested by the decrease in P _va induced by injection of the -adrenoceptor antagonist phentolamine. The cholinergic and the adrenergic tonus affecting heart rate were estimated by injections of atropine and the -adrenoceptor antagonist sotalol. The experiments demonstrate an increased cholicholinergic as well as adrenergic tonus on the heart during hypoxia.     

Coexistence of NADPH-diaphorase and vasoactive intestinal polypeptide in the enteric nervous system of the Atlantic cod (Gadus morhua) and the spiny dogfish (Squalus acanthias)

The distribution of NADPH (nicotinamide adenine dinucleotide phosphate)-diaphorase in nerve cells in the gastrointestinal tract has been investigated and compared in three fish species representing different evolutionary branches. In mammals, NADPH-diphorase is identical to nitric oxide synthase (NOS) and can, in the presence of NADPH, reduce the dye nitroblue tetrazolium, resulting in a blue product. Using this method, we have found numerous NADPH-diaphorase-containing nerve cells in the myenteric plexus of the Atlantic cod (Gadus morhua) and the spiny dogfish (Squalus acanthias) but none in the hagfish (Myxine glutinosa). In the cod, nerve fibres were sparsely stained, whereas in the dogfish, they formed a dense pattern of fibre bundles. Double-staining for NADPH-diaphorase and the neuropolypeptides VIP (vasoactive intestinal polypeptide) and PACAP (pituitary adenylate cyclase activating peptide) revealed three separate populations designated VIP/NADPH, VIP/- and NADPH/-. The majority but not all of the NADPH-diaphorase-positive cells also showed VIP or PACAP immunoreactivity and vice versa. The presence of NADPH-diaphorase in neurons and the distribution of these neurons in the gastrointestinal tract of the two species indicate a physiological role for nitric oxide in the control of gut motility.     

Swimming Performances of Four California Stream Fishes: Temperature Effects

The critical swimming velocity (U_crit) of four California stream fishes, hardhead, Mylopharodon conocephalus, hitch, Lavinia exilicauda, Sacramento pikeminnow, Ptychocheilus grandis, and Sacramento sucker, Catostomus occidentalis was measured at 10, 15, and 20°C. Hardhead, Sacramento sucker, and Sacramento pikeminnow swimming performances tended to be lowest at 10°C, higher at 15°C, and then decreased or remained constant at 20°C. Hitch swimming performance was lower at 10°C than at 20°C. There were no significant differences among species at 10 or 15°C, although pikeminnow and hitch were ca. 20% slower than hardhead or sucker. At 20°C hardhead, Sacramento sucker, and Sacramento pikeminnow had remarkably similar U_crit but hitch were significantly (by 11%) faster. We recommend that water diversion approach velocities should not exceed 0.3ms^–1 for hitch (20–30cm total length) and 0.4ms^–1 for hardhead, Sacramento pikeminnow, and Sacramento sucker (20–30cm TL).     

Modelling Effects of Temperature and Feeding Level on the Life Cycle of the Midge Chironomus Riparius: An Energy-Based Modelling Approach

Survival, growth, emergence and reproduction were monitored during the life cycle of Chironomus riparius in the laboratory at five temperatures from 15 to 27 °C and two feeding diets (ad libitum and limiting). Data were analysed using an energy-based model. Survival was not affected. In ad libitum conditions, growth rate increased linearly with temperature as a consequence of quicker food ingestion. Our model parameterised using the data in ad libitum conditions could account for the data obtained in food limited conditions. Reproduction was not influenced by temperature because the decrease of the duration of the period of energetic investment into reproduction compensated for the increase of the feeding rate when temperature increased. Based on these results, we then built a model describing life cycles in the field which may contribute to the field assessment of the consequences of global warming or pollution.     

海拔梯度变化对黄缘蜾蠃筑巢结构及相关生物学特性的影响

黄缘蜾蠃(Anterhynchium flavomarginatum)是一种以鳞翅目幼虫为食的独栖性捕食昆虫,在生态系统中提供了重要的生物防治功能。2018—2019年,在广东车八岭国家级自然保护区通过人工巢穴收集了不同海拔梯度下(332—1007 m)该蜂的筑巢巢管,系统研究了黄缘蜾蠃的筑巢特征(巢管内径、巢室长度、巢室数量)以及该蜂的子代雌雄数和体型大小随海拔梯度的变化趋势。结果表明：海拔主要影响的是黄缘蜾蠃对巢管内径大小的选择,以及对前庭长度的分配,同时,黄缘蜾蠃对巢管内径的选择可以影响到后代性别比,这种策略主要体现在亲本对雌性子代的投资,而不是雄性子代。研究结果表明黄缘蜾蠃在不同海拔梯度下可根据外界环境压力调整其营巢和生殖策略,以提高种群对环境的适应性。     

Characterization of a collagenolytic serine proteinase from the Atlantic cod (gadus morhua)

A collagenolytic proteinase was purified from the intestines of Atlantic cod by (NH₄)₂SO₄ fractionation, hydrophobic interaction chromatography (phenyl-Sepharose) and ion-exchange chromatography (DEAE-Sepharose). The proteinase has an estimated molecular weight of 24.1 (±0.5) kDa as determined by SDS-PAGE and belongs to the chymotrypsin family of serine proteinases. The enzyme cleaves native collagen types I, III, IV and V, and also readily hydrolyzes succinyl-l-Ala-l-Ala-l-Pro-l-Phe-p-nitroanilide (sAAPFpna), an amide substrate of chymotrypsin, as well as succinyl-l-Ala-l-Ala-l-Pro-l-Leu-p-nitroanilide, a reported elastase substrate, but had no detectable activity towards several other substrates of these proteinases or of trypsin. The pH optimum of the enzyme was between pH 8.0 and 9.5 and it was unstable at pH values below 7. Maximal activity of the enzyme when assayed against sAAPFpna was centered between 45 and 50°C. Calcium binding stabilized the cod collagenase against thermal inactivation, but even in the presence of calcium, the enzyme was unstable at temperatures above 30°C.     

The effect of short-term fasting and a single meal on protein synthesis and oxygen consumption in cod,Gadus morhua

Summary Rates of protein synthesis and oxygen consumption ( O₂) in cod were compared in both fasted and refed animals. During a 14-day fast both protein synthesis and respiration rates fell to stable values after 6 days. When a meal of whole sandeel at 6% body weight was fed to fish fasted for 6 days, protein synthesis and ( O₂) increased to a maximum at between 12 and 18 h after feeding. Peak ( O₂) was about twice the pre-feeding values, while whole animal protein synthesis increased four-fold. There were differences between tissues in the timing of maximum protein synthesis; the liver and stomach responded faster than the remainder of the body. Maximum protein synthesis rates in the liver and stomach occurred at 6 h after feeding, at which time their calculated contribution to total ( O₂) was 11%. Similar calculations suggested that the integrated increment in whole animal protein synthesis contributed between 23% and 44% of the post-prandial increase in ( O₂). It was concluded that protein synthesis is an important contributor to increased ( O₂) after feeding in cod.Abbreviations A _s absolute rate of protein synthesis - ASDA apparent specific dynamic action - ATP adenosine triphosphate - k _s fractional rate of protein synthesis - k _s/RNA amount of protein synthesized per unit RNA - ( O₂) oxygen consumption - PCA perchloric acid - RNA ribonucleic acid     

Co-localization of peptides in the Brockmann bodies of the cod (Gadus morhua) and the rainbow trout (Oncorhynchus mykiss)

Endocrine cells exhibiting immunoreactivity to FMRFamide-like, LPLRFamide-like, neuropeptide Y(NPY)-like and peptide YY(PYY)-like peptides were found in the periphery of the Brockmann bodies of the cod, Gadus morhua, and rainbow trout, Oncorhynchus mykiss. No immunoreactivity or very weak labelling was found with antisera to pancreatic polypeptide (PP). Vasoactive intestinal polypeptide (VIP)-like immunoreactivity was found in nerve fibres, whereas labelling with VIP antiserum in endocrine cells disappeared after preincubation with nonimmune serum. There were always more immunoreactive cells in the rainbow trout than in the cod. No immunoreactivity could be seen with antisera to gastrin/cholecystokinin (CCK) or enkephalin. Double-labelling studies were performed to study the colocalization of the peptides in peripheral endocrine cells. Cells immunoreactive to NPY were also labelled with antisera to FMRFamide, LPLRFamide and PYY. The co-localization pattern of NPY varied; in some Brockmann bodies, a population of the immunoreactive cells showed co-localization and others contained NPY-like immunoreactivity only, whereas in other Brockmann bodies, all NPY-labelled cells also contained FMRFamide-like, LPLRFamide-like and PYY-like immunoreactivity. Cells immunoreactive to PYY similarly contained FMRFamide-like, LPLRFamide-like and NPY-like immunoreactivity, comparable to the patterns observed with NPY. Glucagon-like immunoreactivity was found at the periphery of the Brockmann bodies. A subpopulation of the glucagon-containing cells contained NPY-like immunoreactivity. PYY-like immunoreactivity was also found co-localized with glucagon-like immunoreactivity, as were FMRFamide-like and LPLRFamide-like immunoreactivity. Therefore, either NPY-like and PYY-like immunoreactivity together with FMRFamide-like and LPLRFamide-like immunoreactivity occur in the same endocrine cells of the Brockmann body of the cod and rainbow trout, or a hybrid NPY/PYY-like peptide recognized by both NPY and PYY antisera is present in the Brockmann body.     

Circulating collagen is catabolized by endocytosis mainly by endothelial cells of endocardium in cod (Gadus morhua)

The cells responsible for the clearance of collagen were studied in cod. Cod collagen labelled with the lysosomal trap-label ¹²⁵I-tyramine cellobiose was cleared from the circulation with a t_1/2 of 15 min. 1 h After injection 75%, 17% and 8% of the label were recovered in the heart, liver and blood, respectively. 24 h After administration of collagen labelled conventionally with ¹²⁵I to allow escape of labelled degradation product from the site of uptake, 80% of the label had left the heart, signifying degradation. When collagen was tagged with ¹²⁵I-tyramine cellobiose, heart-associated radioactivity did not decrease after 24 h, indicating intralysosomal degradation. Fluorescence microscopy revealed that i.v. injected fluorescently-labelled collagen accumulated in discrete vesicles of cells lining the endocardial blood space of both atrium and ventricle. Conventional and immuno-electron microscopy showed that these cells contained numerous coated pits and vesicles reflecting active endocytosis, and that ligand lined the limiting membrane of early endosomes. Intravenously injected 2 m latex accumulated mainly in kidney. We conclude that the population of non-macrophagic endocardial cells are important for the turnover of collagen in cod. These cells therefore resemble sinusoidal endothelial cells of salmon kidney and mammalian liver.