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Shell Surface (shell + surface)
Selected AbstractsBehavioural interactions between ecosystem engineers control community species richnessECOLOGY LETTERS, Issue 11 2009Paul E. Gribben Abstract Behavioural interactions between ecosystem engineers may strongly influence community structure. We tested whether an invasive ecosystem engineer, the alga Caulerpa taxifolia, indirectly facilitated community diversity by modifying the behaviour of a native ecosystem engineer, the clam Anadara trapezia, in southeastern Australia. In this study, clams in Caulerpa -invaded sediments partially unburied themselves, extending >30% of their shell surface above the sediment, providing rare, hard substrata for colonization. Consequently, clams in Caulerpa had significantly higher diversity and abundance of epibiota compared with clams in unvegetated sediments. To isolate the role of clam burial depth from direct habitat influences or differential predation by habitat, we manipulated clam burial depth, predator exposure and habitat (Caulerpa or unvegetated) in an orthogonal experiment. Burial depth overwhelmingly influenced epibiont species richness and abundance, resulting in a behaviourally mediated facilitation cascade. That Caulerpa controls epibiont communities by altering Anadara burial depths illustrates that even subtle behavioural responses of one ecosystem engineer to another can drive extensive community-wide facilitation. [source] Mechanisms of egg contamination by Salmonella EnteritidisFEMS MICROBIOLOGY REVIEWS, Issue 4 2009Inne Gantois Abstract Salmonella Enteritidis (SE) has been the major cause of the food-borne salmonellosis pandemic in humans over the last 20 years, during which contaminated hen's eggs were the most important vehicle of the infection. Eggs can be contaminated on the outer shell surface and internally. Internal contamination can be the result of penetration through the eggshell or by direct contamination of egg contents before oviposition, originating from infection of the reproductive organs. Once inside the egg, the bacteria need to cope with antimicrobial factors in the albumen and vitelline membrane before migration to the yolk can occur. It would seem that serotype Enteritidis has intrinsic characteristics that allow an epidemiological association with hen eggs that are still undefined. There are indications that SE survives the attacks with the help of antimicrobial molecules during the formation of the egg in the hen's oviduct and inside the egg. This appears to require a unique combination of genes encoding for improved cell wall protection and repairing cellular and molecular damage, among others. [source] Preferences of the Ponto-Caspian amphipod Dikerogammarus haemobaphes for living zebra musselsJOURNAL OF ZOOLOGY, Issue 3 2009J. Kobak Abstract A Ponto-Caspian amphipod Dikerogammarus haemobaphes has recently invaded European waters. In the recipient area, it encountered Dreissena polymorpha, a habitat-forming bivalve, co-occurring with the gammarids in their native range. We assumed that interspecific interactions between these two species, which could develop during their long-term co-evolution, may affect the gammarid behaviour in novel areas. We examined the gammarid ability to select a habitat containing living mussels and searched for cues used in that selection. We hypothesized that they may respond to such traits of a living mussel as byssal threads, activity (e.g. valve movements, filtration) and/or shell surface properties. We conducted the pairwise habitat-choice experiments in which we offered various objects to single gammarids in the following combinations: (1) living mussels versus empty shells (the general effect of living Dreissena); (2) living mussels versus shells with added byssal threads and shells with byssus versus shells without it (the effect of byssus); (3) living mussels versus shells, both coated with nail varnish to neutralize the shell surface (the effect of mussel activity); (4) varnished versus clean living mussels (the effect of shell surface); (5) varnished versus clean stones (the effect of varnish). We checked the gammarid positions in the experimental tanks after 24 h. The gammarids preferred clean living mussels over clean shells, regardless of the presence of byssal threads under the latter. They responded to the shell surface, exhibiting preferences for clean mussels over varnished individuals. They were neither affected by the presence of byssus nor by mussel activity. The ability to detect and actively select zebra mussel habitats may be beneficial for D. haemobaphes and help it establish stable populations in newly invaded areas. [source] Predatory boreholes in Tournaisian (Lower Carboniferous) spiriferid brachiopodsLETHAIA, Issue 3 2009BERNARD MOTTEQUIN A brachiopod fauna from the uppermost part of the Tournaisian Tournai Formation (Belgium) contains an undetermined species of Crurithyris (Spiriferida, Ambocoeliidae), which displays numerous bored shells. About 8% of the 432 specimens with conjoined valves display single, small (, 1 mm) boreholes, which are smooth-sided, cylindrical or weakly conical, circular to slightly elliptical in plan view, perpendicular to the shell surface and generally complete. Of the 35 bored articulated specimens, 27 were drilled on the ventral valve. Most of the boreholes are located in the posterior half of the shell, and no case of edge-drilling has been observed. The boreholes were drilled by a predator, or possibly a parasite, which selected individuals greater than 2.5 mm long. Crurithyris sp. may have represented an attractive (in terms of energy cost) and easy target for a small-sized predator because of its thin shell and ornament of minute spines. [source] Perspectives of ammonite paleobiology from shell abnormalities in the genus BaculitesLETHAIA, Issue 3 2002R.A. HENDERSON Many Baculites specimens from the Upper Cretaceous of the United States Western Interior show exceptional preservation of the original aragonitic shell and its fine-scale surface ornamentation. Growth lines are ubiquitous, with two orders of these structures represented on some shells, and reflect the incremental addition of new shell at the apertural margin. Growth line interruption in the form of repair of minor shell damage at the aperture, commonplace in contemporary Nautilus, is essentially absent in Baculites, suggesting that its members fed on small prey in the water column. As typical of Mesozoic ammonites in general, and in striking contrast to contemporary Nautilus, no in vivo epizoans have been recognized on specimens of Baculites. It is inferred that the shell of Baculites was covered in periostracum to eliminate epizoic colonization. By analogy with Nautilus, a distinctive micro-ornament oriented at right angles to growth lines and visible on parts of some specimens was probably associated with periostracal attachment. A small proportion of Baculites specimens show abnormalities in shell growth categorized as v-shaped indentations of growth lines, shell grooves, fine-scale folds on the surface of growth lines and feather structures. We view this entire set of structures as due to abnormalities in mantle growth induced at the leading edge, impressed into the periostracum during its fabrication, and then in turn into the shell surface. As many of the Baculites with shell abnormalities are smooth, the proposal by Checa linking homologous structures recognized on other ammonites to the formation of comarginal ribs is rejected. A case of sutural inversion, in which the form of minor divisions of the major saddles and lobes are transposed, is recognized in a specimen of Baculites codyensis Reeside. We consider sutural pattern in ammonites, an expression of septal fluting, as replicating the genetically specified standing form of an elastic adapical visceral mass. The inverted sutural pattern, and by implication the style of septal fluting, was transcribed exactly in the three successive septa preserved on the specimen. The abnormality appears to be a case of homeotic mutation in which the plan for one body region becomes translocated to another. The conservatism of major elements of sutural (=septal) patterns for Mesozoic ammonites in their evolutionary spectrum suggests that a homeobox of conserved DNA sequence, with the transcription factors encoded in homeotic genes, is likely to have been involved. [source] Preserving boiled eggs with a sterilization system employing microbial laccase and wood vinegarANIMAL SCIENCE JOURNAL, Issue 6 2007Hiromichi SAKAGUCHI ABSTRACT A combination of a microbial laccase and wood vinegar was used to treat the shell surface of boiled eggs. The laccase enhanced the sterilization effect of phenolic compounds contained in the wood vinegar and resulted in prevention of microbial infection of the boiled eggs after storage for 21 days at 40°C and 75% relative humidity. Significant phenoxy radicals, formed by the catalytic reaction of the laccase, could be detected in the shell of the boiled eggs. [source] Quantifying sponge erosions in Western Australian pearl oyster shellsAQUACULTURE RESEARCH, Issue 9 2010Sabine Daume Abstract This paper describes several methods to estimate the amount of sponge erosion in pearl oyster shells (Pinctada maxima Jameson, 1901). Internal erosion can be calculated from non-destructive surface area estimates because a clear relationship was found between the eroded area on the surface of the shells and internal erosions. Grading shells into three different categories, according to the severity of erosion, also proved to be a suitable method to quickly assess the amount of sponge erosions. All methods were more accurate in shells with larger amounts of erosions. Using the described methods, the Lacepedes fishing ground was more diverse in bioeroding sponge species compared with sites at the 80-Mile fishing ground locations. Pione velans Hentschel, 1909 was the dominant bioeroding sponge species but Cliona dissimilis Ridley and Dendy, 1886 eroded more shell material than P. velans. Observed patterns suggest that P. velans had a more recent recruitment than C. dissimilis. We suggest that visual grading together with estimates from the shell surface will be sufficient to determine the general long-term trends in bioeroding sponge severity. However, results of monitoring programmes need to be supplemented by histological examination to confirm sponge activity and species identity. [source] Are extrasolar oceans common throughout the Galaxy?ASTRONOMISCHE NACHRICHTEN, Issue 8 2007D. Ehrenreich Abstract Light and cold extrasolar planets such as OGLE 2005-BLG-390Lb, a 5.5 Earth masses planet detected via microlensing, could be frequent in the Galaxy according to some preliminary results from microlensing experiments. These planets can be frozen rocky- or ocean-planet, situated beyond the snow line and, therefore, beyond the habitable zone of their system. They can nonetheless host a layer of liquid water, heated by radiogenic energy, underneath an ice shell surface for billions of years, before freezing completely. These results suggest that oceans under ice, like those suspected to be present on icy moons in the Solar system, could be a common feature of cold low-mass extrasolar planets. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Formation of wrinkled shell surfaces in ammonitesLETHAIA, Issue 3 2003ANTONIO G. CHECA No abstract is available for this article. [source] | |||||||||||||