Occurrence of Pomphorhynchus laevis Müller 1776 (Acanthocephala) in Silurus glanis (L.) from the River Po.

The sheatfish, Silurus glanis (L.), from the terminal part of River Po was examined for the presence of helminth parasites. Of 182 S. glanis specimens, 95 (52.2%) were infected with the acanthocephalan Pomphorhynchus laevis. Mid-gut followed by fore-gut appeared to be the most infected portions of host alimentary canal. In 45 sheatfish of total length < or = 40 cm, specimens of P. laevis were found encapsulated in mesenteric and peritoneal tissues. A comparison between light and electron microscopy on features and stages of testis development in both encapsulated male P. laevis and intestinal male parasites showed that the encysted acanthocephalans were immature; mature spermatozoa were rarely found within the testis of worms from the alimentary canal. Among extraintestinal P. laevis specimens, the presumable eversion of parasite praesoma was observed and described. The results of the present survey suggest that small-size individuals of S. glanis could be used as paratenic host by P. laevis during its life cycle in the study area.     

Genetic characterization of 18 novel microsatellite loci in northern pike (Esox lucius L.)

The northern pike (Esox lucius L.), an important predatory freshwater species, is undergoing significant population decline. In this study, 18 novel polymorphic microsatellite loci were isolated and used for assessing genetic variation in the Chinese Ulungur and Hungarian Balaton populations of the species. The number of alleles ranged from 2 to 13, observed heterozygosity from 0.154 to 0.920 and expected heterozygosity from 0.145 to 0.921, thereby indicating the specific usefulness of these suites of markers for investigating genetic variability.     

A study of a polymorphic globulin in the serum of Silurus glanis L.

A polymorphism of S-globulin was detected in serum of Silurus glanis L. by starch gel electrophoresis. Three phenotypes were observed which are apparently controlled by two codominant alleles, Sg^A and Sg^B , of an autosomal locus, Sg . Although on electrophoresis S-globulin and transferrin have similar mobilities, the properties of the two proteins differ.     

Mitochondrial DNA variation in European populations of Silurus glanis

Mitochondrial DNA diversity of 13 wild Silurus glanis populations (covering the entire range of the species) and eight hatchery populations was investigated. PCR-RFLP analysis of four regions of mitochondrial DNA (cytochrome b, control region, ND-5/6) was used. Nineteen haplotypes were found. Thirteen of them were private. The proportion of total genetic diversity attributable to population differentiation was almost 80%. Despite the existence of significant differentiation between populations for mtDNA variation, no consistent pattern of geographic structuring was revealed and nucleotide divergence among S. glanis populations was low. These phenomena are discussed with regard to the impact of glaciation events. The domesticated stocks show less genetic diversity than natural ones, possibly due to their mode of management. Analysis of three European catfish species S. glanis, S. aristotelis and Silurus triostegus (sampled in the Euphrates river) revealed several endonucleases which produced restriction phenotypes diagnostic for the three species.     

Identification of juvenile natural hybrids between Atlantic salmon (Salmo solar L.) and trout(Salmo trutta L.)

The identification of two wild salmonid smolts, suspected to be hybrids between Atlantic salmon ( Salmo salar ) and trout ( S trutta ) on morphological grounds, was confirmed by electrophoretic separation of serum proteins. A third, trout-like, hybrid was identified in a sample of parr. Hybrids showed presence of both parent types of esterase, prealbumin and transferrin.     

Shift in pike, Esox lucius L., predation pressure following the introduction of ruffe, Gymnocephalus cernuus (L.) to Loch Lomond

Rapid and dramatic change in the fish community of Loch Lomond has resulted from a series of fish introductions in recent years. A comparison of the diet of pike, Esox lucius L., in 1989–1990 with data from 1955–1967, prior to recent introductions, demonstrates a shift in prey choice. In 1955–1967 powan, Coregonus lavaretus (L.), dominated in the diet (57% of prey by number) by 1989–1990 the introduced ruffe, Gymnocephalus cernuus (L.), was the commonest prey species (44% by number). This shift in pike predation to an abundant population of introduced ruffe has consequences for native species. Assuming that the pike population has not increased in response to increased food availability due to the introduction of ruffe, pike predation pressure on native species will be relieved. This is likely to have the greatest effect on powan. Comparison of the predation rate in 1955–1967 with 1989–1990 supports the hypothesis that the rate of predation on powan has declined, although the effect that this may have on the powan population is unclear, as the role of predation in the regulation of population size is unknown for this species.     

Hydroperoxide-dependent epoxidation of unsaturated fatty acids in the broad bean (Vicia faba L.)

Incubation of linoleic acid with the 105,000g particle fraction of the homogenate of the broad bean (Vicia faba L.) led to the formation of the following products: 13(S)-hydroxy-9(Z),11(E)-octadecadienoic acid, 9,10-epoxy-12(Z)-octadecenoic acid (9(R),10(S)/9(S)/10(R), 80/20), 12,13-epoxy-9(Z)-octadecenoic acid (12(S),13(R)/12(R)/13(S), 64/36), and 9,10-epoxy-13(S)-hydroxy-11(E)-octadecenoic acid (9(S),10(R)/9(R),10(S), 91/9). Oleic acid incubated with the enzyme preparation in the presence of 13(S)-hydroperoxy-9(Z),11(E)-octadecadienoic acid or cumene hydroperoxide was converted into 9,10-epoxyoctadecanoic acid (9(R),10(S)/9(S),10(R), 79/21). Two enzyme activities were involved in the formation of the products, an omega 6-lipoxygenase and a hydroperoxide-dependent epoxygenase. The lipoxygenase, but not the epoxygenase, was inhibited by low concentrations of 5,8,11,14-eicosatetraynoic acid and nordihydroguaiaretic acid. In contrast, the epoxygenase, but not the lipoxygenase, was readily inactivated in the presence of 13(S)-hydroperoxy-9(Z),11(E)-octadecadienoic acid. Studies with 18O2-labeled 13(S)-hydroperoxy-9(Z),11(E)-octadecadienoic acid showed that the epoxide oxygens of 9,10-epoxyoctadecanoic acid and of 9,10-epoxy-13(S)-hydroxy-11(E)-octadecenoic acid were derived from hydroperoxide and not from molecular oxygen.     

Astaxanthin binding to solubilized muscle proteins of Atlantic salmon (Salmo salar L.), haddock (Melanogrammus aeglefinus L.) and Atlantic halibut (Hippoglossus hippoglossus L.)

A study was conducted to compare astaxanthin binding ability of solubilized muscle proteins of Atlantic salmon (Salmo salar L.), haddock (Melanogrammus aeglefinus L.) and Atlantic halibut (Hippoglossus hippoglossus L.). Muscle proteins of juvenile Atlantic salmon, haddock and halibut were solubilized by sequential extraction of muscle tissue using low ionic strength solutions. Electrophoretic protein profiles of the six solubilized fractions from these species were similar. Each solubilized fraction from the three species was examined for its relative astaxanthin binding capacity. The amount of bound astaxanthin was significantly different (P < 0.05) among the six fractions of each species. Significant differences in astaxanthin binding were only found for fractions A and E among the species. The amount of bound astaxanthin in various fractions of each species showed a good correlation (R² = 0.80–0.92) with the ANS (8-anilino-1-naphthalenesulfonate) fluorescence intensity of those fractions. The pattern and extent of astaxanthin binding to the muscle proteins of juvenile salmon, haddock and halibut is comparable to that reported previously for adult Atlantic salmon [Saha, M.R., Ross, N.W., Gill, T.A., Olsen, R.E., Lall, S.P., 2005. Development of a method to assess binding of astaxanthin to Atlantic salmon S. salar L. muscle proteins. Aquacult. Res. 36, 336–343.]. These combined observations suggest that the carotenoid binding capacity of the muscle proteins of salmon is not the limiting factor in the deposition of carotenoid in their flesh.     

Polyphenism ofHalictus (Seladonia) tumulorum (L.) (Hymenoptera,Halictinae)

Summary A population ofHalictus (S.) tumulorum, a species whose biology is poorly known, was studied in eastern France. The polyphenism was evaluated by comparing a sample of foundresses (1991) with two samples of summer females (1991 and 1992).H. tumulorum is a primitively eusocial species with castes differing only slightly in size, but more in function, and producing numerous males in the first brood. The social level of the species appears rather low.     

Investigation on carp, Cyprinus carpio L. gynogenesis

A reliable method for gynogenetic mass-production has been developed in carp ( Cyprinus carpio L.). The effect of different cold shock treatments applied after fertilization were examined. The yield of viable diploid gynogenetic animals could be significantly increased when the cold shock was applied 5 min or 15 min after fertilization. A negative correlation has been found between the effectiveness of these two treatments, so both were used on separate batches of eggs. By means of gynogenesis, the crossover frequency and map distance of the transferrin locus have been determined. Successful pilot experiments were made on grass carp ( Ctenopharyngodon idella Val.) and sheatfish ( Silurus glanis L.) with respect to gynogenetic mass production.     

Early life migration patterns of Baltic Sea pike Esox lucius

This study investigated the movement patterns of Baltic Sea pike Esox lucius in Matsalu Bay, Estonia, using otolith microchemistry. Migration patterns of E. lucius were remarkably diverse, but distinct groups were evident. Of the E. lucius analysed (n = 28), 82% hatched in fresh water and 74% of them left this biotope during the first growth season.     

The life cycles of Leptophlebia vespertina (L.) and L. marginata (L.) (Ephemeroptera) in Llyn Dinas, North Wales

Data is presented on the life cycles of Leptopblehia vespertina (L.) and L. marginata (L.) in Llyn Dinas, an oligotrophic North Wales lake. Both species are univoltine and growth continues throughout the winter although somewhat retarded. Except during July and August there is a clear size separation of the two species, L. marginata being larger and emerging earlier. The egg incubation period was determined directly from laboratory studies. The results are discussed in relation to previous research in the English Lake District.     

Polymorphism of transferrin in carp (Cyprinus carpio L.): Genetic determination,isolation, and partial characterization

Seven transferrin variants (A, B, C, D, E, F, and G) have been found in carp sera (Cyprinus carpio L.). Genetic analysis involves five variants and agrees with the hypothesis of simple codominant autosomal inheritance at one transferrin (Tf) locus in spite of the fact that the carp is a tetraploid in relation to other species of the same family. Carp populations from three regions were studied which differed in gene frequencies. Individual populations were in Hardy—Weinberg equilibrium. The polymorphism of carp transferrins can be used for the identification of offspring of single parent pairs, stocked in one pond. Transferrins have been isolated and characterized. Homozygous phenotypes comprised four iron-binding components differing in electrophoretic mobility. This heterogeneity is not caused by sialic acid, which is absent. Amino acid composition, content of hexoses (1 mole/mole of protein) and hexosamines (1 mole/mole of protein), molecular weight (70,000), and the isoelectric point (5.0) have been determined. No N-terminal amino acid could be detected.     

Methane yield and species diversity dynamics of perennial wild plant mixtures established alone,under cover crop maize (Zea mays L.), and after spring barley (Hordeum vulgare L.)

The cultivation of perennial wild plant mixtures (WPMs) in biogas cropping systems dominated by maize (Zea mays L.) restores numerous ecosystem functions and improves both spatial and temporal agrobiodiversity. In addition, the colorful appearance of WPM can help enhance landscape beauty. However, their methane yield per hectare (MYH) varies greatly and amounts to only about 50% that of maize. This study aimed at decreasing MYH variability and increasing accumulated MYH of WPM by optimizing the establishment method. A field trial was established in southwest Germany in 2014, and is still running. It tested the effects of three WPM establishment procedures (E1: alone [without maize, in May], E2: undersown in cover crop maize [in May], E3: WPM sown after whole‐crop harvest of spring barley [Hordeum vulgare L.] in June) on both MYH and species diversity of two WPMs [S1, S2]). Mono‐cropped maize and cup plant (Silphium perfoliatum L.) were used as reference crops. Of the WPM treatments tested, S2E2 achieved the highest (19,296 , 60.5% of maize) and S1E1 the lowest accumulated MYH (8,156 , 25.6% of maize) in the years 2014–2018. Cup plant yielded slightly higher than S2E2 (19,968 , 62.6% of maize). In 2014, the WPM sown under maize did not significantly affect the cover crop performance. From 2015 onward, E1 and E2 had comparable average annual MYH and average annual number of WPM species. With a similar accumulated MYH but significantly higher number of species (3.5–10.2), WPM S2E2 outperformed cup plant. Overall, the long‐term MYH performance of WPM cultivation for biogas production can be significantly improved by undersowing with maize as cover crop. This improved establishment method could help facilitate the implementation of WPM cultivation for biogas production and thus reduce the trade‐off between bioenergy and biodiversity.     

Using anglers' records in Poland as a tool for assessing changes in fish body weight caused by fluctuations of inland water quality

Anglers' records of fish weight (ARFW) were analysed in Poland for the periods 1965–1989 (successive increases in inland water pollution), and 1990–2010 (considerable improvements in water quality). For the initial ARFW analysis, the entire study was divided into nine intervals of 5 years each; the period that followed was divided into three catchments: the Vistula, Oder and Pomeranian rivers, whereby 10 species were chosen to represent obligatory riverine and facultative species. With a few exceptions, the investigated species showed unexpected and varying reactions to the changes in water quality. The ARFW of obligatory riverine barbel Barbus barbus (L.) decreased during the first periods (1965–1989), then increased significantly from 1990 to 2010. For obligatory riverine ide Leuciscus idus (L.), tendencies were less clear but as significant. However, other obligatory riverine species have not shown a relationship between ARFW and water quality. Discrepancies were also recorded in the facultative riverine pike (Esox lucius L.) and brown trout (Salmo trutta L.). Considering the number of medals recorded, there were some interesting tendencies related to the decline or improvement in the water quality, although not in all investigated species. The species displaying a decrease in medals awarded from 1966 to 1989 and increasing after 1990, was chub Leuciscus cephalus (L.), but only until 2005. Species which showed successive increases in awards from 1989 to 2010 were: pike, perch (Perca fluviatilis L.), ide, and wels (Silurus glanis L.). However, for species in the period when the water quality actually deteriorated (1966–1990), the number of medals awarded increased: barbel, brown trout (S. trutta L.), and grayling Thymallus thymallus (L.).     

Site fidelity and seasonal changes in activity centre size of female pike Esox lucius in a small lake

The object of this study was to test site fidelity of female pike Esox lucius and to contrast the activity centre size in summer and winter in a 25 ha lake in north-eastern Germany using radio telemetry. Weekly 24 h tracking and two 96 h tracking exercises were conducted by boat from June to December 2005 and by walking on surface ice from January to February 2006. Positions of 12 E. lucius [total length ( L _T) = 450–733 mm] were recorded every 3 h within a 24 h tracking cycle. Site fidelity to individual summer activity centres was tested by translocating eight E. lucius away from their activity centre. All translocated E. lucius returned to their summer activity centre within 6 days, which provided evidence of site fidelity of E. lucius . There was no relation between E. lucius L _T or the translocation distance and return time to the activity centre after translocation. In winter, the activity centre size of E. lucius was significantly larger than in summer, but there was considerable overlap between the sites chosen in winter and those in summer. The seasonal variation in activity centre size possibly reflected changes in habitat structure ( e.g . collapse of structured vegetated habitats in winter) or prey fish distribution.     

The relative duration of similar periods in the early embryogenesis of teleosts

The absolute (in min.) and relative (in the number of tau0) duration of the periods of cleavage, epiboly and that between the onset of gastrulation and the stage of 10 pairs of somites were determined in Cyprinus carpio L., Misgurnus fossils L., Esox lucius L. and Coregonus peled Gmel. at different constant temperatures. The stability of the dimensionless characteristics for the duration of each of these periods in the species in question within the limits of optimum temperatures was shown. A comparison of the relative duration of the same periods of early embryogenesis in C. carpio, M. fossilis, E. lucius, Salmo trutta L. morpha fario and S. gairdneri Rich. has shown that in the species under comparison the relative durations of the period of synchronous cleavage divisions are similar, whereas those of the period of asynchronous cleavage divisions differ. The relative durations were found to be similar for the period between the onset of gastrulation and the stage of 10 pairs of somites in M. fossilis, E. lucius and 2 species of Salmo. Differences were revealed in the relative duration of the period of epiboly; the average relative rate of the movement of blastoderm cells toward the vegetative pole is similar in the species with the eggs of small size (C. carpio, M. fossilis, Coregonus peled) and increases with the egg size. The temporal relationships between the embryonic periods under study in the species in question and possible mechanism which determine these relationships are considered with respect to the data on egg structure, as well as on the stage when the isolated blastoderm acquires the capacity of differentiation in vitro.     

Effects of photoperiod, feeding regime and water temperature on the formation of daily growth increments in otoliths of larval pike (Esox lucius L.)

Otolith growth increments of larval pike, Esox lucius L., were examined using known-age fish reared in the laboratory. Under different photoperiod, feeding, and temperature regimes, increments in the lapilli of all laboratory-reared fish were formed daily, starting on day 2–3 after hatching.

Zusammenfassung

Der Einfluß van Photoperiode, Futterrhythmus und Wassertemperatur auf die Anlage von Otolithen-Tagesringen bei jungen Hechten (Esox lucius L .)
Die Anlage von Tagesringen auf den Otolithen von Hechtlarven ( Esox lucius L. ) wurde unter verschie-denen Licht-, Futter- und Temperaturbedinungen im Labor untersucht. Bei allen Tieren setzte die Bildung von Tagesringen auf den Lapilli zwei lis dreiTage nach dem Schlüpfen ein.     

Genetic tags applied to the European hake, Merluccius merluccius (L.)

Three biochemical gene markers test the hypothesis that the European hake, Merluccius merluccius (L.), along the west European continental shelf are one race. The three polymorphic loci were serum transferrin (Tf), eye vitreous fluid butyric esterase (Es) and liver superoxide dismutase (Sod). Five transferrin alleles, three esterase alleles and two superoxide dismutase alleles were identified. Heterogeneity tests on genotype frequency distribution for twelve areas ranging from Norway to Biscay revealed no significant variation. The results using these genetic tags are consistent with the unit race hypothesis for hake throughout the sea areas sampled.     

Genetic structure and phylogeography of European catfish (Silurus glanis) populations

The genetic structure of Silurus glanis (Europe's largest freshwater fish species) across most of its natural distribution was investigated using 10 microsatellite loci. The revealed levels of genetic diversity were much higher than previous allozyme and restriction fragment length polymorphism mitochondrial DNA analyses had shown; relative levels of variability among populations were however, in good agreement with the previous studies. Populations from large basins (Volga and Danube rivers) were the most polymorphic, while samples from the smaller Greek rivers, which are more prone to genetic bottleneck, exhibited the lowest levels of genetic diversity. Microsatellite multilocus genotyping permitted the assignment of individual fish to their population of origin with a score as high as 98.3%. Despite the great genetic differentiation of S. glanis populations, no consistent pattern of geographical structuring was revealed, in contrast to previous studies of European freshwater fish species. A model of isolation by distance seems more probable and a hypothesis of recent dispersion from only one glacial refugium is proposed. The discovery of the highest levels of microsatellite and mitochondrial diversity in the Volga sample and the presence of river connections, during the Pleistocene, between this area and all major areas of the present catfish distribution, place this refugium around the Ponto-Caspian region. Combining these data with those from previous studies, a number of markers are now available to monitor wild and hatchery populations even at the individual level.