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  • 1
    ISSN: 1439-0426
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Cross-species amplifications of microsatellite locus Spl-106, which was originally screened from the genome of shovelnose sturgeon (Scaphirhynchus platorynchus) with a perfect TAGA repeat motif, were carried out in four other species of the genera Acipenser. A total of 34 polymerase chain reaction (PCR) products representing 16 different alleles of this locus was sequenced. Sequence analysis results showed that besides the number changes of repeat units, many mutational events, such as single-base substitutions and various insertion/deletion (indels) occurred not only at species level but also at individual level, even among the different alleles within the same individual. The repeat motifs varied from perfect (TAGA)n array to perfect compound (TAAA)m (GAAA)n and perfect or imperfect compound (TAAA)m (TAGA)n (TAAA)x arrays in different species and different individuals. The evolution dynamics of this locus in sturgeons was inferred in that it may evolve from a single perfect to different perfect or imperfect compounds.
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  • 2
    Electronic Resource
    Electronic Resource
    Berlin, Germany : Blackwell Verlag GmbH
    Journal of applied ichthyology 21 (2005), S. 0 
    ISSN: 1439-0426
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Berlin, Germany : Blackwell Verlag GmbH
    Journal of applied ichthyology 21 (2005), S. 0 
    ISSN: 1439-0426
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1439-0426
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Four microsatellites were used to examine the genetic variability of the spawning stocks of Chinese sturgeon, Acipenser sinensis, from the Yangtze River sampled over a 3-year period (1999–2001). Within 60 individuals, a total of 28 alleles were detected over four polymorphic microsatellite loci. The number of alleles per locus ranged from 4 to 15, with an average allele number of 7. The number of genotypes per locus ranged from 6 to 41. The genetic diversity of four microsatellite loci varied from 0.34 to 0.67, with an average value of 0.54. For the four microsatellite loci, the deviation from the Hardy–Weinberg equilibrium was mainly due to null alleles. The mean number of alleles per locus and the mean heterozygosity were lower than the average values known for anadromous fishes. Fish were clustered according to their microsatellite characteristics using an unsupervised ‘Artificial Neural Networks’ method entitled ‘Self-organizing Map’. The results revealed no significant genetic differentiation considering genetic distance among samples collected during different years. Lack of heterogeneity among different annual groups of spawning stocks was explained by the complex age structure (from 8 to 27 years for males and 12 to 35 years for females) of Chinese sturgeon, leading to formulate an hypothesis about the maintenance of genetic diversity and stability in long-lived animals.
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  • 5
    ISSN: 1439-0426
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Ontogenetic and spatial variability in microhabitat use of spined loach Cobitis taenia (Linnaeus), considered as one species for the purposes of this study, and stone loach Barbatula barbatula (Linnaeus) were examined in the River Great Ouse basin, England, using multivariate and habitat suitability methods, including a technique for handling spatial variation in collections of preference curves. Distinct ordinations of spined age classes and stone loach developmental stages, respectively, in canonical correspondence analysis of species × variables × samples relationships suggest that the two species occupy completely different microhabitats; however, young-of-the-year spined loach occurred more often than expected with all developmental stages of stone loach except young larvae. Water velocity and filamentous algae were the most influential microhabitat variables, the latter decreasing in importance with increasing age of both fish species. Preferred water velocities generally decreased with age in spined loach and increased in stone loach, with substratum size generally increasing with fish age in both species. Spatial variation in microhabitat preferences was great in both species but less so in the spined loach, suggesting that limited plasticity in habitat use could account, at least in part, for the latter species’ limited distribution and abundance in the catchment. Preference curves for a species, if generated and verified for all life intervals and all seasons, could be used as a management tool for a given stream or sector of river basin. But preference curves should be generated for each location to ensure that river management decisions with regard habitat and species conservation consider local-level species requirements. Thus, a multi-(eco)species and multi-scale approach is required in habitat suitability assessments.
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  • 6
    ISSN: 1439-0426
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The unexpected discovery of extensive intraindividual variation of the 18S rRNA gene in nine North American species of sturgeon (and its absence in the North American paddlefish) was described in a previous paper by Krieger and Fuerst (2002b). As part of the study, genomic 18S rRNA genes from a lake sturgeon (Acipenser fulvescens) individual were amplified by polymerase chain reaction (PCR), cloned and sequenced, resulting in the identification of at least 17 different sequence variants. Because of the number of variants detected and the improbability that such a large number of different alleles are required for survival, these sequence variants were subjected to further analyses (sequence comparison, phylogenetic and relative rate) to examine the possibility that some variants may be pseudogenes. The cDNA produced by reverse transcriptase (RT)-PCR amplification of 18S rRNA isolated from lake sturgeon liver tissue was also sequenced. The topology of the phylogenetic tree produced suggests a split of the sequence variants into two groups: paddlefish-like (PL) alleles and non-paddlefish-like (NPL) alleles. Relative rate comparisons of these two groups indicate that the alleles within the NPL allele group are evolving more quickly than those in the paddlefish-like (PL) group, and so are likely under relaxed functional constraints. Less than one-third of nucleotide changes in the non-paddlefish-like (NPL) alleles occur at positions that are considered to be highly conserved in a universal eukaryotic model of rRNA structure. No substitutions at eukaryotic universally conserved sites occur in the PL alleles. Analysis of the sequence of the RT-PCR product shows that a single lake sturgeon 18S rDNA sequence variant is expressed in major quantities in the liver, and that this single product is identical to the allele most similar in sequence to the paddlefish. These results provide support for the idea that many variants are unimportant for proper cellular function or are pseudogenes. Although concerted evolution has apparently failed to homogenize the many rDNA sequence variants found within sturgeon, the detection of a single major expressed sequence variant in lake sturgeon indicates that the expression of the variants is in fact under the control of selective factors.
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  • 7
    Electronic Resource
    Electronic Resource
    Berlin, Germany : Blackwell Verlag GmbH
    Journal of applied ichthyology 20 (2004), S. 0 
    ISSN: 1439-0426
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1439-0426
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: An experimental investigation was carried out on sardines (Sardina pilchardus W.) with the aim to evaluate the influence of sex and total length (TL) on total weight (TW) and fillet weight (FW), chemical composition, and lipid fraction quality. Special emphasis was given with respect to the content of polyunsaturated fatty acids (PUFA), which are considered important from a dietary, nutritional, and functional point of view. Sardines were subdivided as a function of TL and sex. Four groups were obtained: (i) males, TL 130–155 mm, (ii) males, TL 155–180 mm, (iii) females, TL 130–155 mm, (iv) females, TL 155–180 mm. Fatty acid composition and chemical analyses were subsequently carried out on the sardine fillets; results showed higher TW and FW in female sardines and higher percentage value of FW/TW ratio in male sardines, indicating a higher incidence of viscera and other non-edible parts in females than in males. Moreover, total lipids were on average significantly higher (P 〈 0.05) in longer specimens (TL = 155–180 mm) than in shorter ones (TL = 130–155 mm). Finally, total saturated fatty acids (SFA) and total mono-unsaturated fatty acids (MUFA) values were found to be significantly higher in females than in males; such values increased significantly (P 〈 0.01) only for total SFA from shorter to longer sardines. As for total PUFA, both ω6 and ω3 were found to be higher in male than in female sardines and significantly higher (P 〈 0.001) in larger than in smaller sizes. Total PUFA/total SFA ratio were in all cases close to 1, with higher values in male than in female sardines and in larger than in smaller specimens.
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  • 9
    ISSN: 1439-0426
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: We studied the demand-feeding behaviour was studied of gilthead seabream (Sparus aurata, L.) reared under either constant (25 ± 0.5°C, 12 : 12 L : D, control group) or natural (experimental group) temperature and photoperiod conditions during a period from winter to summer. Hourly demand-feeding activity profiles were recorded using self-feeding devices; these profiles showed that control group behaved entirely as a diurnal species, exhibiting no nightly activity and decreased demand rates in winter months. The experimental group did exhibit nightly activity (in incomplete darkness); this group also showed reduced demand rates in winter months, accompanied by a demand peak shift towards evening/night hours that followed the day's temperature peak of colder months.
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  • 10
    ISSN: 1439-0426
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: To examine the possibility of dietary α-starch in reducing feed costs in a practical diet, α-starch was supplemented at 10, 20, 30 and 40% in a composed diet having the same protein level. The four diets were fed to ayu, Plecoglossus altivelis (initial weight 9.1 g) for 43 days. Growth and feed efficiency increased with the supplement, with values highest in the 30–40%α-starch diet. The level of dietary α-starch did not affect the proximate muscle composition; although the hepatosomatic index was not affected, liver glycogen increased with increasing dietary α-starch. The dietary α-starch did not influence evacuation time from the gut, and was well digested through passage in the gut, mainly between the stomach and the anterior part of the intestine. Ayu have an ability to adapt their metabolism to high dietary α-starch, and can digest 40% or more in a composed diet. Although the muscle lipid content did not change, the fatty acid composition was influenced by dietary starch. With the elevation of dietary starch, a decrease of C18:2n-6 and an increase of C22:6n-3 occurred. These results indicate that at least 40%α-starch can be used in practical diets for ayu.
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