Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Electronic Resource  (18)
Source
Material
  • Electronic Resource  (18)
Years
Keywords
  • 1
    Electronic Resource
    Electronic Resource
    The insidious effect of diatoms on copepod reproduction (1999)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 402 (1999), S. 173-176 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The productive regions of the ocean are characterized by seasonal blooms of phytoplankton which are generally dominated by diatoms. This algal class has, therefore, traditionally been regarded as providing the bulk of the food that sustains the marine food chain to top consumers and important ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/46023
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Relationships between dissolved free amino acids, chemical composition and growth of the marine diatom Chaetoceros debile (1983)
    Springer
    Marine biology 77 (1983), S. 93-100 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The release of dissolved free amino acids in axenic batch cultures of the diatom Chaetoceros debile during different growth phases was studied during the late summer of 1982. Variations due to ASP, HIS, ALA, SER, THR, PHE+NH4, LEU and ORN were observed. The proportions of each amino acid differed according to growth phase. Maximum release and accumulation in the medium, corresponding to a rise ranging from 10-8 to 10-6 M, occurred at the transition between the exponential and stationary phases, and coincided with a shift in the intracellular protein and carbohydrate concentrations, and in the chlorophyll: phaeophytin ratio. It is suggested that zooplankton grazers can benefit from the accumulation of phytoplankton standing stock and nutritious compounds at times when the concentration of extracellular amino acids is high enough to trigger chemosensory detection of algal food; i.e., at the end of the exponential growth phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00393214
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Feeding of Pseudocalanus minutus on living and non-living particles (1976)
    Springer
    Marine biology 34 (1976), S. 117-125 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A seasonal study of carbon content of living and of carbon and nitrogen content of non-living particulate material in seawater is presented. Grazing by Pseudocalanus minutus on living and non-living particles has been investigated over 1 year. Seasonal variations in the food uptake were associated with seasonal variations of each chemical component of the particles in the water. The amount of non-living carbon constituted the major part of the food ingested, irrespective of season. The ingested living carbon always accounted for a small fraction of the total copepod body carbon. The proportion of living carbon ingested could be equivalent to or even higher than non-living carbon at times during the late spring, summer and fall. The concentration of both living and non-living material within each particle peak of the spectra in the water seemed to affect the balance between non-living and living particle uptake. Non-living particles cannot be considered only as a supplementary food source for small copepods; they are a basic food for P. minutus at all times.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00390753
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Appendage activity recordings of the sub-Antarctic copepod Drepanopus pectinatus in relation to its feeding behaviour (1991)
    Springer
    Polar biology 11 (1991), S. 431-438 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Movements of the cephalic appendages of nauplii (stages 3 and 4), copepodites (stage 4) and adult female Drepanopus pectinatus were investigated using a computerized micro-impedance unit. Direct measurements and visual observations of the behaviour of restrained copepods were made in the presence of filtered seawater, naturally occurring phytoplankton of different sizes, prefiltered extracts of phytoplankton and seston. The normal appendage movements recorded in filtered seawater were similar for adult females and copepodites. Traces for nauplii were different compared with those of the two other developmental stages. Appendage movements were modified when adult females were offered particles of different sizes and extracts of phytoplankton, showing significant changes in the frequency of the limb beats in relation to each stimulus. Impedance traces distinguished between activity of copepod appendages related to feeding and to swimming such as: flicking, stroking, jerking, combing, handling and rejecting particles. Prolonged recordings of restrained females in association with visual observations suggested that the activity of the mandibular palp was related to gut fullness and peristaltic movements, and to fecal pellet formation and evacuation. These results indicated that D. pectinatus is an intermittent beater responding to the physical and chemical characteristics of food.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00233078
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Feeding rates and diel vertical migration of copepods near South Georgia: comparison of shelf and oceanic sites (1992)
    Springer
    Marine biology 114 (1992), S. 49-56 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Seventeen Longhurst Hardy Plankton Recorder profiles were taken over a diel cycle in January 1990 to study the feeding of four major copepods over the South Georgia shelf. Ontogenetic changes in vertical migration were followed and feeding cycles determined by gut fluorometry for Calanoides acutus Stage CV, Calanus sinillimus CV and CVI♀, C. propinquus CV and Rhincalanus gigas CV and CVI♀. In common with a neighbouring oceanic site visited two weeks later and reported elsewhere, all four species had a diel cycle of feeding and migration. The vertical distributions of C. simillimus (all stages), R. gigas (nauplii) and Euphausia frigida (postlarvae) were similar at both sites, the night being spent within the chlorophyll maximum at 15 to 30 m. However, the biomass dominants, C. acutus and R. gigas, dwelt below the chlorophyll maximum, about 30 m deeper than their oceanic counterparts. Unlike the oceanic site, feeding at the shelf site was not restricted to darkness, but increased 6 to 10 h before nightfall and finished at dawn; the intervening period coincided with sinking and digestion. Daylight feeding may have been induced by the shorter night, lower light levels or greater food requirements at the shelf site, despite planktonic predators being over three times more abundant. Daily ration estimates for R. gigas at both sites were only ∼2% body carbon per day. These low values contrast with its smaller competirors, whose rations were in the range 5.6 to 27%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00350855
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    A comparative study of the inhibitory effect of diatoms on the reproductive biology of the copepod Temora stylifera (1995)
    Springer
    Marine biology 121 (1995), S. 533-539 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Egg production and viability in the copepod Temora stylifera (collected in the Bay of Naples, Italy in 1992) were strongly dependent on food type. A flagellate (Isochrysis galbana) diet induced the production of good quality eggs that developed to hatching. By contrast, two diatoms (Chaetoceros curvisetum, Phaeodactylum tricornutum) resulted in poor egg quality, with hatching success as low as 20% of total egg production. With the third diatom tested, Skeletonema costatum, females produced eggs for only 3 to 4 d, after which time they either became sterile or died. These results are discussed in relation to previous findings regarding the impact of the dinoflagellate Prorocentrum minimum and the diatom Thalassiosira rotula on the hatching success of T. stylifera eggs. Low egg viability was possibly not due to an absence of remating or a deficiency of some specific essential nutrient required for egg development but to the presence of inhibitory compounds blocking cell division during early copepod embryogenesis. This questions the traditional view that diatoms are an important food item regulating copepod secondary production.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00349463
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Water-soluble extracts of the diatom Thalassiosira rotula induce aberrations in embryonic tubulin organisation of the sea urchin Paracentrotus lividus (1999)
    Springer
    Marine biology 134 (1999), S. 147-154 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Eggs and embryos of the sea urchin Paracentrotus lividus were used as a model to study the effect at the cellular level of potential anti-mitotic compounds extracted from the diatom Thalassiosira rotula. Eggs and embryos incubated in a water-soluble diatom extract, corresponding to 5 × 106 and 107 cells ml−1, were totally blocked (i.e. cell division was blocked) at the one-cell stage. At lower concentrations (2.5 and 1.25 × 106 cells ml−1), the first mitotic division was inhibited in 32 ± 26% and 25 ± 3.5% of the zygotes, respectively, demonstrating the dose-dependent effect of diatom extracts on sea urchin development. Immunofluorescence dyes, specific for DNA and α-tubulin subunits, were used to stain nuclei and microtubules in sea urchin embryos during various phases of development. Images with the confocal laser scanning microscope showed that tubulin was not organised in filaments at the sperm aster and cortex levels, and that the pronuclei were not fused in embryos incubated soon after fertilisation with water-soluble diatom extracts corresponding to 107 cells ml−1. At lower diatom-extract concentrations (4 × 106 cells ml −1), fusion of the pronuclei occurred but the mitotic spindle was not formed. Microtubules were clearly de-polymerised and the chromatin appeared globular and compacted at the centre of the cell. A similar structure was observed for sea urchin embryos incubated with 0.1 mM colchicine, a potent anti-mitotic compound. When sea urchin embryos were incubated in water-soluble diatom extracts at different times prior to the first mitotic division, microtubules appeared de-polymerised at each step, from pronuclear fusion to telophase, and cell division was blocked. At the histological level, embryos incubated with 4 × 106 cells ml−1 diatom extract showed nuclear fragmentation without cytokinesis. The possible use of sea urchin embryos as a bioassay to test for other unknown compounds with cytotoxic activity in phytoplankton species is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002270050533
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Seasonal grazing of Pseudocalanus minutus on particles (1974)
    Springer
    Marine biology 25 (1974), S. 109-123 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Grazing by Pseudocalanus minutus on naturally occurring partieles has been investigated over a 2 year period at 5 m depth, in a small coastal embayment in Nova Scotia, Canada. Large variations in the standing stock of particulate matter in the water from 5 m depth were associated with seasonal changes in phytoplankton, and at times with runoff from rivers. Each size group displayed seasonal changes, with high amplitudes occurring in the large-particle size ranges. P. minutus consumption was associated with seasonal changes in total particle concentration as well as with the concentration in each size group. The food uptake was correlated (P〉0.01) with the particle concentration in all particle categories, except in the size range below 3.57 μ. Frequency of positive electivity indices increased with particle sizes up to 57 μ and then decreased. Observations on particle spectra revealed considerable seasonal variability in both particle sizes and copepod feeding patterns. P. minutus adapted to seasonal variations within the particle spectrum by shifting its grazing pressure from one size range to another. By taking advantage of every particle peak concentration, P. minutus revealed a strong opportunistic feeding behaviour, and a very efficient utilization of the standing stock. Maximum consumption was recorded in early spring, when P. minutus fed on large-size particles. Feeding took place in the medium and small-size ranges during the summer and part of fall. Food uptake was rarely less than 2.26% of body weight during the winter, and reached up to 55% and sometimes more in spring. The unselective feeding patterus demonstrated by P. minutus suggest certain ecological implications of feeding pressure on standing stock.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00389260
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Variation in Vitamin C content of sprat larvae (Sprattus sprattus) in the Irish Sea (1991)
    Springer
    Marine biology 108 (1991), S. 39-48 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Sprat (Sprattus sprattus) eggs and larvae were sampled from plankton and the Irish Sea in 1988 and 1989 and analysed forl-ascorbic acid (Vitamin C) content, which is considered an index of the nutritional well being and thus indicative of the status of the population in relation to environmental (physical and biological) structures. In one month, the Vitamin C content of larvae in different developmental stages decreased from 800 to 300µg g−1 in the youngest larvae (4 to 14 mm) and to 250µg g−1 in the oldest larvae (14 to 28 mm). No significant differences in the Vitamin C content per unit weight were found between larvae collected at four sites located in western stratified waters, central stratified, central mixed and eastern mixed waters. The mean Vitamin C content per larva, as well as mean length and wet weight of larvae were lowest in central mixed and eastern mixed waters in May–June. The estimated increases in Vitamin C, length and weight of individuals in the population of larvae varied significantly from April to June and between western stratified and eastern mixed areas. Highest rates coincided with stratified water conditions and with suitable quantity and quality of food, which seemed to constitute the most favourable environmental conditions for abundance and growth of sprat larvae.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01313469
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Co-occurrence of copepods and dissolved free amino acids in shelf sea waters (1991)
    Springer
    Marine biology 108 (1991), S. 373-385 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The vertical distribution of chlorophylla, copepods, dissolved free amino acid concentration and the fixation of14C by phytoplankton were monitored in the springs of 1983, 1987 and 1988 in the Ushant front region, shelf edge of the Celtic Sea and central Irish Sea, respectively. In each area, two stations characterized by mixed and stratified water conditions were compared. Vertical distributions of amino acids coincided with the distribution of copepods. A positive and significant correlation was found between the abudance of copepods and the concentration of amino acids dissolved in seawater. A negative and significant correlation was found between chlorophylla and the concentration of amino acids. Enrichment of amino acids (≥ 20 to 500 nM l−1 at specific depths) due to aspartic and glutamic acids, glutamine and ornithine, was assumed to reflect copepod feeding activity and faecal production. At these depths, the natural concentration and diversity of amino acids, including aspartic acid, glutamic acid, asparagine, serine, histidine, glutamine, arginine, threonine, glycine, alanine, tyrosine, valine, phenylalanine, ornithine and lysine, were high enough and in the correct proportions for triggering feeding and swimming and swarming behavior of copepods, as well as their remote detection of food at the micro- and meso-scales (1 to 10 m). This accumulation of amino acids also constitutes a potential additional source of organic nitrogen for bacteria and phytoplankton.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01313646
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...