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  • 1
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    Application of video-endoscopy to the study of bivalve feeding on toxic dinoflagellates (1998)
    In:  EPIC3Application of video-endoscopy to the study of bivalve feeding on toxic dinoflagellates, Xunta de Galicia and Intergovernmental Oceanographic Commission (UNESCO), Santiago de Compostela, Spain, Reguera, B., J. Blanco, M.L. Fernandez, T. Wyatt (Eds.), pp. 453-456
    Details
    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
    Type: Inbook , peerRev
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  • 2
    Electronic Resource
    Electronic Resource
    Improved modeling of surface charge distributions in electret ionization chambers (1994)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 730-735 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Additional considerations are discussed concerning the modeling of time-dependent surface charge distributions in electret ionization chambers during the charging and discharging of electrets with ionizing radiation. Estimates of position-dependent ion density in the charging chamber are made using (a) a single-scattering calculation of ionization due to recoil electrons and (b) an isotropic, inverse-square approximation of ionization density. These estimates are used in conjunction with a subroutine which solves Laplace's equation for electric field and tracks charge carrier trajectories from the point of origin in the chamber to an electret surface where the charge becomes trapped. The results of improved measurements are also shown and compared with calculations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1145093
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  • 3
    Electronic Resource
    Electronic Resource
    Modeling of surface charge distributions in electret ionization chambers (1993)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 64 (1993), S. 1627-1632 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Computer modeling of the change of electret surface-charge distribution within electret ionization chambers (EIC) during the electret charging and discharging processes are described. Assuming a uniform and constant rate of ion generation, the theory of ion recombination in air is applied to Laplace's equation to develop a description of the rate of charge accumulation and surface charge distribution. It is shown that distortions of electric fields within the air gap of the EIC control the distribution of charge accumulation, while saturation conditions, that determine the level of recombination of charges within the air gap of the EIC, control the maximum potential that can be deposited onto the electret surface. Results of modeling are compared with measured data, and suggestions for refinement in the model are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1144037
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  • 4
    Electronic Resource
    Electronic Resource
    Influence of temperature and food availability on the ecological energetics of the giant scallop Placopecten magellanicus (1987)
    Springer
    Oecologia 72 (1987), S. 550-556 
    Details
    ISSN: 1432-1939
    Keywords: Placopecten magellanicus ; Scallop ; Reproductive effort
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Gonad output, reproductive effort and residual reproductive value are greater in scallops (Placopecten magellanicus) from shallow water, where conditions are more favourable, than in scallops from deep water. Variation between years in these fitness correlates is also greater in shallow water scallops. High reproductive effort is associated with a greater reproductive cost, although in general reproduction in this species appears to be “restrained”, and only in older individuals from shallow water is there evidence of “reckless” reproductive behaviour. Reproductive effort increases as the animal grows older, but residual reproductive value is a maximum at age 4 years, after which it decreases with age owing to greater mortality. Localities vary in their suitability for scallop growth and reproduction, and at one Newfoundland site conditions in shallow water (10 m) are better than those in deep water (31 m). Scallops from the former have a greater fitness than those from the latter. The energy costs of reproduction have implications for life history variability in P. magellanicus, although for a considerable part of its lifetime the scallop is able to maximise gamete production in response to environmental factors (especially the food supply) without trading off reproduction against growth or maintenance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00378981
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  • 5
    Electronic Resource
    Electronic Resource
    Exfoliation of epithelial cells by the scallop Placopecten magellanicus : seasonal variation and the effects of elevated water temperatures (1997)
    Springer
    Marine biology 127 (1997), S. 463-472 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Previous studies have shown that large numbers of ciliated and nonciliated epithelial cells (diam.: 6 to 15 μm) are released by adult sea scallops, Placopecten magellanicus (Gmelin), during summer months in Newfoundland when water temperatures are at a maximum and gonads are well developed. Such exfoliation of cells could be a response to stresses associated with elevated water temperatures and/or spawning activity. In the present study an electronic particle counter/sizer was used to further investigate the factors that influence exfoliation of epithelial cells by juvenile and adult scallops throughout the year. We observed release of epithelial cells from juveniles, and from adults collected in months when gametogenic activity was minimal, indicating that exfoliation does not occur as a result of reproductive activity alone. SEM analysis revealed little difference in surface characteristics of the gills, mantle and gonad between scallops that had released cells and those that had not, suggesting that exfoliation of small numbers of cells may be a consequence of cellular turnover and normal physiological function. Adult scallops were monitored in a second experiment to determine the effects of raising water temperatures from 8.5 to 14.7 and to 21.0 °C on the frequency (proportion) and rate of cellular exfoliation. Only at the highest experimental temperature (21.0 °C) were exfoliation rates significantly higher than rates recorded at 8.5 or 14.7 °C. SEM analyses revealed some damage to gill, mantle and gonad tissues when scallops were exposed to 14.7 and then to 21.0 °C for a total of 8 d.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002270050034
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  • 6
    Electronic Resource
    Electronic Resource
    Direct observations of feeding structures and mechanisms in bivalve molluscs using endoscopic examination and video image analysis (1991)
    Springer
    Marine biology 111 (1991), S. 287-291 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A new technique is described for observing the structures and mechanisms of suspension feeding in bivalves using endoscopic examination and video image analysis. This method permits direct in vivo observations of whole, intact structures of relatively undisturbed specimens. No surgical alterations of shell or tissue are required for most species. Pallial organ activity can be recorded for future observations and analysis. Using this technique we examined three bivalve species, each with different degrees of mantle fusion:Mya arenaria L.Mytilus edulis L., andPlacopecten magellanicus (Gmelin). The specimens were collected between April and September 1990 at various locations in Trinity Bay, Newfoundland, Canada. Particle retention by the gill and transport of material to the palps was observed, and velocity of particles moving on the gill was determined. We demonstrate that the endoscope-video-analysis system is an efficient and affordable technique suitable for studies of pallial organ function and mechanisms of feeding.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01319711
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  • 7
    Electronic Resource
    Electronic Resource
    Lipid composition of eggs and adductor muscle in giant scallops (Placopecten magellanicus) from different habitats (1992)
    Springer
    Marine biology 113 (1992), S. 71-76 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Scallops (Placopecten magellanicus Gmelin) were collected during August 1989 from shallow water (10 m) and deep water (31 m) habitats at Sunnyside, Trinity Bay, Newfoundland, to compare the lipid composition of eggs and adductor muscle tissue. Less favorable food levels and lower temperature conditions associated with deeper water have previously been shown to produce slower growth and reduced fecundity in individuals from this habitat. Triacylglycerol reserves consistently accounted for 60% of the total lipids present in both groups. The total lipid content of the eggs and the composition of their triacylglycerol fatty acid pools were similar in shallow water and deep water scallops, indicating very little if any nutritional difference between the two groups. Relative to their counterparts from shallow water, individuals from deeper water contained higher proportions of docosahexaenoic acid [22:6(n-3)] in the egg phospholipids and higher levels of 24-methylenecholesterol (a phytosterol commonly found in diatoms) in the adductor muscle. Differences in fatty acid composition are interpreted as biochemical adjustments of cell membranes to increase membrane fluidity, thereby compensating for the lower temperatures prevailing at the greater depth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00367640
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  • 8
    Electronic Resource
    Electronic Resource
    Distribution and abundance of choanoflagellates (Acanthoecidae) in the coastal cold ocean of Newfoundland, Canada (1997)
    Springer
    Marine biology 129 (1997), S. 407-416 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Water samples from six bays were taken over a 5-year period (1988 to 1992) to determine the distribution and abundance of loricate choanoflagellates in coastal Newfoundland, and to assess the impact that these organisms might have on this cold ocean food web. Scanning electron microscopy was used to study the morphology of these flagellates, allowing us to identify 11 species of loricate choanoflagellates. Parvicorbicula socialis (Meunier) Deflandre was the most abundant species (80 × 103 cells l−1), particularly during the spring diatom bloom. Single-cell species, such as Bicosta spini fera (Throndsen) Leadbeater and Calliacantha natans (Grontved) Leadbeater, were found more commonly after the spring diatom bloom in the summer months. Many of the single-cell choanoflagellates were attached to bacteria-rich microaggregates and debris in the water column and in unpoisoned sediment traps. The P. socialis cell flux was calculated to be 5.3 × 106 cells m−2 d−1 in late May sediment traps. P. socialis in the upper 100 m of the water column was removing 0.3% of the standing crop of bacteria each day (April/May), and the equivalent of 7.4% of the daily bacterial production over the water column. Diel studies of P. socialis in Conception Bay suggest that the sharp decline in population numbers observed in midnight samples may be related to the high number of grazing zooplankton observed during the same period. Pelagic tunicate and zooplankton fecal pellets were found to contain large numbers of choanoflagellate costae, thus providing a direct link from the microbial loop to the macrozooplankton.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002270050181
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  • 9
    Electronic Resource
    Electronic Resource
    Age determination of the soft-shell clam Mya arenaria using shell internal growth lines (1980)
    Springer
    Marine biology 58 (1980), S. 105-109 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Shells of known-age Mya arenaria have revealed an internal annual growth pattern in this bivalve. The number of external growth rings on the shell exterior does not correspond to the age of the clams. This study provides an alternative method to using external annual rings for age determination. The internal growth lines are visible in thin sections when the shells are cut from the umbo to the ventral margin. The lines are formed by late spring of each year prior to spawning and are probably in response to decreased winter growth. When the 7 year olds were examined it was difficult to distinguish the most recent growth line and the inner shell layer. This could result in ages being underestimated. This annual pattern of internal growth lines could be useful to biologists and paleoecologists engaged in population studies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00396121
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  • 10
    Electronic Resource
    Electronic Resource
    Influence of temperature and food availability on the ecological energetics of the giant scallop Placopecten magellanicus (1986)
    Springer
    Marine biology 93 (1986), S. 37-48 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Scallops (Placopecten magellanicus) were collected in 1981–1983 from two water depths at a location in Newfoundland, Canada, where temperature and food conditions associated with shallower water have been shown to be more favourable for somatic growth and gamete production. To gain insight into the seasonal energy balance for this species, metabolic and clearance rates were measured monthly under ambient temperature conditions and natural seston levels. Stereological techniques were used to determine the gamete volume fraction in the gonad in order to establish the annual reporductive cycle. The less favourable conditions associated with deeper water were relfected in reduced rates of gamete development, but the diameter of spawned eggs and the timing of spawning appeared unaffected by poorer conditions in the natural environment. Estimates of scope for growth were low or negative during the winter, but consistently high during the spring bloom, corresponding to a period of rapid gamete maturation. Somatic weight declined in both populations as gamete development proceeded but increased again during periods of low gametogenic activity, suggesting a close relationship between energy available for growth and the reproductive cycle. Oxygen uptake and clearance rate varied seasonally in relation to ambient temperature and food conditions, all of which appeared to be interrelated in a complex fashion with the energy demands of gametogenesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00428653
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