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  • 1
    Electronic Resource
    Electronic Resource
    Genetic structure of populations of two species of Chthamalus (Crustacea: Cirripedia) in the north-east Atlantic and Mediterranean (1997)
    Springer
    Marine biology 128 (1997), S. 73-82 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Protein electrophoresis on starch gels was used to investigate population genetic structure of the barnacles Chthamalus montagui Southward and C. stellatus (Poli) over their north-east Atlantic and Mediterranean ranges. In each species, a single locus exhibited marked differentiation of allele frequencies between Atlantic and Mediterranean localities; in C. stellatus, genetic differentiation between the two basins had not previously been noted. In both species, mean heterozygosity per locus appeared higher in the Mediterranean samples than in the Atlantic, and Mediterranean populations had more alleles at the loci studied. Possible explanations for the differentiation between the Atlantic and the Mediterranean populations are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002270050070
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  • 2
    Electronic Resource
    Electronic Resource
    Effects of long-term physical disturbance by commercial scallop fishing on subtidal epifaunal assemblages and habitats (2000)
    Springer
    Marine biology 137 (2000), S. 325-337 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  This paper examines spatial differences in the distribution of by-catch assemblages from the scallop [Pecten maximus (L.) and Aequipecten opercularis (L.)] fishing grounds in the North Irish Sea, during 1995. The sites examined have been exposed to differing known levels of fishing disturbance by scallop dredging, based on unusually high-resolution data extracted from fishermens' logbooks. Uni- and multi-variate techniques have been used on a production dataset (a value which incorporates both abundance and biomass figures), as well as abundance and biomass data individually. The original species list was reduced to higher taxonomic groupings in line with the theory that the latter is more appropriate for detecting anthropogenic change. Species diversity and richness, total number of species, and total number of individuals all decrease significantly with increasing fishing effort. Species dominance increases with effort. Total abundance, biomass and production, and the production of most of the major individual taxa investigated decrease significantly with increasing effort. Multivariate analysis reveals a significant relationship between fishing effort and by-catch assemblage structure. The taxa most responsible for the differences are the echinoids and cnidarians, but prosobranch molluscs and crustaceans also contribute to the differences. By-catch assemblage structure is more closely related to fishing effort than any other environmental parameter investigated, including depth and sediment type. We observed an approximately linear decrease in diversity with increasing fishing disturbance, and suggest this is primarily due to selective removal of sensitive species and, more importantly, habitat homogenisation. These results were interpreted in the light of ecological theories relating disturbance to community structure. The argument that invertebrate scavenger populations benefit from prolonged exposure to fishing disturbance was also examined, but no supporting evidence was found.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002270000357
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  • 3
    Electronic Resource
    Electronic Resource
    Population differentiation and taxonomic status of the exploited limpet Patella candei in the Macaronesian islands (Azores, Madeira, Canaries) (1996)
    Springer
    Marine biology 125 (1996), S. 141-152 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract There has been considerable confusion in the taxonomy of limpets of the North East Atlantic Ocean and Mediterranean Sea, particularly those from the Macaronesian islands. The present study compared populations of the intertidal limpet Patella candei d'Orbigny from the Azores, Madeira and the Canaries with those of P. caerulea Linnaeus and P. depressa Pennant from the European and African continental coasts. No major differences in radular morphology were detected between the three species. However, electrophoretic analysis of 15 enzyme loci gave overall genetic identity (I) values of ∼0.5 between the three species, indicating that they cannot be regarded as conspecific as previously thought, and suggesting that P. candei is endemic to the Macaronesian islands. Comparisons of P. candei within these islands showed that, although populations did not differ with respect to radular morphology and soft-body parts, populations from the Azores were distinct from those in Madeira and the Canaries in shell shape and gene frequencies. Individuals from the Azores had, no average, taller shells and longer radulae, while those in Madeira and the Canaries had a shallow, depressed and stellate shell form. This was interpreted as being due to the wider habitat distribution of the species in the Azores compared to Madeira and the Canaries. Electrophoretic results showed that P. candei from the Azores differed from P. candei in Madeira and the Canaries by almost 40% of the loci investigated (I=0.660), suggesting that the former is a separate endemic species. An I value of 0.969 between populations in Madeira and the Canaries was typical of conspecific populations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00350768
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  • 4
    Electronic Resource
    Electronic Resource
    A study of the structure of zinc polycarboxylate dental cements (1993)
    Springer
    Journal of materials science 4 (1993), S. 32-35 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Two examples of zinc polycarboxylate dental cement were studied, one of which was prepared from an aqueous solution of poly (acrylic acid) together with the zinc oxide powder, the other being prepared by adding water to a mixture of dried polyacid and zinc oxide powder. The changes in the properties of the resultant cements with length of storage in various media were determined. In all cases the maximum strength was achieved fairly rapidly, usually at 1 week, after which there was little or no increase. Cements stored in water achieved the lowest compressive strengths, whereas cements stored in highly desiccating conditions, over concentrated sulphuric acid, achieved very high (if variable) compressive strengths. There appeared to be very little difference between the water-activated and conventional cements. These results confirm previous findings that zinc polycarboxylate cements are relatively poorly hydrated compared with other polyelectrolyte biomaterials. This in turn implies that water does not play a structural role in these cements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00122974
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  • 5
    Electronic Resource
    Electronic Resource
    The incorporation of hydroxyapatite into glass-polyalkenoate (“glass-ionomer”) cements: a preliminary study (1993)
    Springer
    Journal of materials science 4 (1993), S. 418-421 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: The effect of adding finely divided hydroxyapatite (HAp) powder to glass-polyalkenoate cements has been studied. Two different glasses were used in cement formation, an oxide and a fluoride glass. Cements were prepared at a powder: liquid ratio of 2:1, higher ratios being unattainable because of the low bulk density (hence large volume fraction per unit mass) of HAp powder. For the oxide glass there was a steady reduction in compressive strength and an increase in working and setting times with increased loadings of HAp. By contrast, for the fluoride glass, there was a plateau region from 2.5 to 40% by mass HAp in the glass powder in which the compressive strengths and the working and setting times remained approximately constant. At HAp levels above 40%, as for the oxide glass, there was a significant reduction in strength and an increase in working and setting times. The presence of HAp in the cement was not found to inhibit the development of compressive strength with time for cements prepared from the fluoride-containing glass. Cements prepared from the oxide glass, by contrast, did not increase in strength with time and this feature was also not changed by the presence of HAp.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00122202
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  • 6
    Electronic Resource
    Electronic Resource
    Monitoring rocky-shore communities: a critical look at spatial and temporal variation (1980)
    Springer
    Helgoland marine research 33 (1980), S. 484-494 
    Details
    ISSN: 1438-3888
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Increasingly programmes are being set up to monitor rocky-shore communities in order to provide baseline data which will indicate changes resulting from subsequent pollution. However, these efforts are complicated by several factors. Firstly, there are overall changes in the composition of communities both within and between years. Secondly, there is variation within certain communities due to a mosaic distribution of components, the mosaic format changing continuously with a cycle of several years. This paper reports on studies of a medium-exposed rocky shore in the Isle of Man (U. K.). It describes patterns of spatial and temporal variation, and looks at certain implications for monitoring programmes: (a) the frequency of sampling, and the duration of the sampling programme, in the light of seasonal and long-term variation; (b) the efficiency, in terms of the minimisation of variability, of sampling the same area by different strategies — belt transects, small random quadrats, single large quadrat; (c) the effect of the distribution patterns of some commoner species on the variation between samples.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02414773
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  • 7
    Electronic Resource
    Electronic Resource
    The influence of epilithic microbial films on the settlement of Semibalanus balanoides cyprids – a comparison between laboratory and field experiments (1998)
    Springer
    Hydrobiologia 375-376 (1998), S. 203-216 
    Details
    ISSN: 1573-5117
    Keywords: barnacle ; biofilm ; cypris ; recruitment ; fouling ; microalgae ; succession ; rocky ; intertidal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Barnacle cypris larvae show considerable exploratory behaviour prior to habitat selection. The influence of natural epilithic microbial fouling organisms on the settlement of Semibalanus balanoides cyprids (Crustacea: Cirripedia) was examined using laboratory and field based investigations. In choice chambers, cues from microbial films were important; cyprids preferred surfaces with a mature microbial film to either unfilmed surfaces or those with a developing film. Cyprids also discriminated between filmed rocks from different tidal heights, preferentially selecting those from the mid-shore which is their usual zone. Filmed surfaces which had previously been colonised by barnacles were selected in preference to unfilmed surfaces, but the presence of an adult barnacle did not enhance settlement on either filmed or unfilmed surfaces. However, laboratory experiments were not consistent with settlement in the field which was predominantly influenced by the proximity of conspecifics and by traces of previous barnacle colonisation. These factors increased settlement, and seemed to over-rule cues from microbiota within the film. Difficulties in the application of laboratory based studies to settlement in the natural environment are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1017036301082
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  • 8
    Electronic Resource
    Electronic Resource
    Feeding behaviour in Littorina littorea: a study of the effects of ingestive conditioning and previous dietary history on food preference and rates of consumption (1990)
    Springer
    Hydrobiologia 193 (1990), S. 191-198 
    Details
    ISSN: 1573-5117
    Keywords: feeding ; preference ; learning ; phagostimulant ; intertidal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Feeding responses of the generalist herbivore, Littorina littorea (L.), to the perceived ‘taste’ of macroalgae were assessed with respect to the effects of recent dietary intake and to overlapping versus nonoverlapping distributions of winkles and algae. The extent of grazing on artificial substrates impregnated with crude algal extracts was used as a measure of rate of response to the odour of preferred algae, and of feeding preference among less preferred algae, in a variety of designs. Adult L. littorea collected from a site where a range of algae were present showed preference among extracts of fucoids, whereas adults from a nearby site showed no such preference. Juvenile L. littorea of two weight cohorts collected from the former site responded faster to Porphyra umbilicalis extract-containing substrate than similar-sized animals from the latter site. Juveniles, fed either Porphyra, Ulva lactuca, or starved for two weeks in the laboratory, responded similarly to Ulva versus Porphyra extracts in a dose-dependent manner across a range of concentrations, although the Porphyra-maintained group consumed more of each, and the starved group less over seven days. Juveniles maintained on a mixed diet of Ulva and Porphyra consumed more Porphyra extract and less Ulva extract over the same period. These results are discussed in relation to the possible role of ingestive conditioning and previous dietary history in determining the occurrence and extent of chemically-mediated feeding preference in L. littorea.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00028076
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  • 9
    Electronic Resource
    Electronic Resource
    Scraping a living: a review of littorinid grazing (1990)
    Springer
    Hydrobiologia 193 (1990), S. 117-138 
    Details
    ISSN: 1573-5117
    Keywords: feeding behaviour ; algal defences ; intertidal ecology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Littorinid snails are predominantly herbivorous and the versatility of their radulae enables them to feed on a variety of macroscopic and microscopic plants in a diversity of habitats. Some are selective feeders preferring some species of algae to others, and rejecting some even after a prolonged period of starvation. Different species of snail exhibit different preferences. The factors affecting the attractiveness and edibility of food plants are discussed and food value considered. Foraging behaviour of littorinids is briefly reviewed in relation to the influence of chemical cues from the algae. Littorinids appear to be able to select or reject algae without having ingested them, having perceived the plants from a distance, moving towards favoured foods (or habitat-providing plants) and away from those that it rejects. The nature of the chemical cues emitted by the algae is discussed. Temporal patterns of foraging activity show some evidence of an endogenous component which can be overridden by responses to environmental conditions. These patterns place restraints on energy intake. The structural and chemical defences used by algae against littorinid grazing are considered. The importance of polyphenolic compounds is evaluated. The effects of grazing as a selective agency and a factor influencing algal populations are discussed. There is some evidence that life history patterns are a response to grazing. The influence of external physical factors, such as salinity on grazing pressure is demonstrated. Finally, the impact of littorinid snails on intertidal communities is assessed in relation to their abundance and biogeographical distribution. The relative importance of littorinids is contrasted on shores possessing or lacking limpets.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00028071
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  • 10
    Electronic Resource
    Electronic Resource
    Putative sense organs on the palliai tentacles of the limpet, Patella vulgata (L.) (1983)
    Springer
    Cell & tissue research 231 (1983), S. 663-674 
    Details
    ISSN: 1432-0878
    Keywords: Ciliary tuft ; Pallil tentacles ; Patella vulgata ; Sensory ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The structure and ultrastructure of ciliary tufts on the pallil tentacles of the limpet Patella vulgata (L.) are described. The tip of each tentacle is covered by a dense crown of tufts and additional tufts can be seen scattered evenly across the surface of each tentacle. The cilia are nonmotile and nerve fibres run from the base of the ciliated cells suggesting a sensory function. Comparisons are made with ciliary tufts found in a Pacific species of limpet, Acmaea scutum, and other molluscan sensory structures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00218124
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