The evolution of the cemented habit in the bivalved molluscs

The ability to cement to a hard substratum has evolved repeatedly in the bivalved molluscs. Twenty clades of cementing bivalves have been identified from a broad range of bivalve taxa. Such polyphyletic acquisition of the habit raises a number of questions concerning the preadaptations which allow bivalves to cement and the selection pressures which favour this mode of attachment. Detailed examination of cementation in members of the Ostreidae reveals that a calcareous extra-periostracal cement is responsible for attachment. Spherulitic growth of cement, whose composition is identical to that of the shell layers, results in structures reminiscent of diagenetic cements. These observations suggest that extrapallial fluid leaks' through a permeable periostracum; resulting in precipitation of calcium carbonate between the periostracum and the substratum. Similar observations are made for most other living shell cementing bivalves, implying a convergence of mechanism. The only exception are the chamids which appear to utilise a weaker organic bond. Less than 10% of fossil Chamacea are preserved attached to their substrata, suggesting that this weaker mode of attachment has been employed in this superfamily throughout its evolutionary history. Having established a common mechanism by which most bivalves cement it is possible to suggest the possible preadaptations. Principal requirements are the possession of a thin and 'leaky' periostracum, a highly extensible mantle edge and a suitable life orientation. Indeed, most cementing bivalves have evolved from pleurothetic byssate stock. The Pectinidae, in which the cemented habit has evolved at least four times, are shown to possess these key preadaptations. Mytiloids have never cemented despite having members which have dwelt on hard substrates since the Ordovician. Examination of modem Mytilacea suggests that the group lacks all the fundamental preadaptations for cementation. There is little evidence to support the traditional view that cementation is an adaptation to life in a high energy environment. The independent appearance of many of the cementing clades during the early Mesozoic coincides with the increased predation pressure which has been documented for that time. A causal link is implied by experimental work: predators display a significant preference for more easily manipulated byssate prey

Experimental actinomycosis: The pathogenic action of Actinomycetes in mice

Hitherto, laboratory investigations into the disease actinomycosis have been almost wholly restricted to cultural and serological studies of the causal organism, Actinomyces israelii. The reason for this limitation is lack of a method of inducing a satisfactory infection in laboratory animals. 2 The literature on actinomycosis contains many references to unsuccessful attempts to infect laboratory animals. There are also accounts of methods of infection which succeeded only irregularly or depended upon methods which introduced such a degree of artificiality that the resulting infections were of little value for any comparative purposes - for example, the testing of therapeutic substances that might be used. for the treatment of actinomycosis in man or domestic animals. A critical review of the relevant literature is presented. By inoculating mice with cultures of A. israelii grown in thioglycollate broth I found that lesions developed in the inoculated animals with sufficient regularity to suggest the usefulness of further investigation of the disease so produced in mice. Success in establishing a useful experimental infection in mice probably depended on three influences; (1) the use of fluid matures grown for a relatively short period (4 - 5 days), which gave high yields of infective material; (2) the U80 of "rough" strains of A. israelii; and (3) awareness that non-fatal lesions developed in the inoculated animals. 4. A comparative study of the lesions so produced in mice and of those found in natural infections of the human, subject showed moray striking points of similarity between the two. 5. Histological studies of organs of infected mice revealed the presence of abscesses in liver and spleen but not in other organs. The abscesses showed branching filaments of Actinomyces arranged in a radial disposition, giving a picture closely akin to that of the "sulphur granule" typical of the lesions found in natural infection of man, In the mouse, clubs at the edge of the lesion wore net observed; co that the picture approximated more closely to that found In man than to that observed in bovines. By killing animals at different times after inoculation I found that the abscesses underwent spontaneous regression from about 6 weeks after inoculation. 6. In fluid culture A. israelii may grow either in the rough form with long branching, a characteristic deposit, and clear supernatant or in the smooth form with diphtheroid morphology and even turbidity throughout the medium. The lesions in mice already described were produced by inoculation of the rough form. When inoculated, into mice, smooth cultures gave rise to macroscopic lesions which superficially appeared to be similar to those produced by the organism in the rough filamentous form, bat a clear difference in the tissue reaction was shown by histological examination. With smooth cultures nothing like a sulphur granule was seen, the diphtheroids did not give rise to branching filaments in the animal and large lipophagic macrophages were not seen. 7. Among the mice which recovered from the initial actinomycotic infection but died at 6 months after inoculation, some showed, tubular nephritis, which is a type of lesion not previously described in mice. Other survivors of the initial infection died at about 12 - 18 months after inoculation; these did not show the presence of tubular nephritis, Attempts were made on a limited, scale to produce tubular nephritis in mice by endotoxins of A. lsraelii, The results, though inconclusive, were suggestive they are given and discussed in the thesis, Experiments were also carried out to compare the action of two other members of the order Actinogyeetales with that of israelii upon insolation into mice, Nocardia asteroides aerobic acid-fast branching and relatively uncommon pathogen of man and animals produced a fatal infection in the mouse, Abscesses formed in liver, spleen and kidney. Contrary to what was found with A. israelii the kidney became a focal point of the experimental infection which was invariably fatal within two months. The type of lesion and tissue reactions were entirely different from those produced by A. israelii. Actinomyces graminins, the aerobic saprophyte aerobic saprophyte commonly found in grasses, had no effect upon mice, whether the inoculum employed was in the sporing or non-sporing phase. 9. The experimental infections thus produced with A. israelii in mice are reproducible if the necessary care is taken to observe the details of method emphasised in this thesis as important. The findings assist in establishing the status of the organism as an undoubted pathogen but of low virulence. The experimental infection has obvious uses in assessing the value of chemotherapy and for studying the pathology of the disease. In this connection the renal lesions would appear to merit particular attention

Ocean acidification does not impact shell growth or repair of the Antarctic brachiopod Liothyrella uva (Broderip, 1833)

Marine calcifiers are amongst the most vulnerable organisms to ocean acidification due to reduction in the availability of carbonate ions for skeletal/shell deposition. However, there are limited long-term studies on the possible impacts of increased pCO2 on these taxa. A 7 month CO2 perturbation experiment was performed on one of the most calcium carbonate dependent species, the Antarctic brachiopod Liothyrella uva, which inhabits the Southern Ocean where carbonate ion saturation levels are amongst the lowest on Earth. The effects of the predicted environmental conditions in 2050 and 2100 on the growth rate and ability to repair shell in L.uva were tested with four treatments; a low temperature control (0°C, pH7.98), a pH control (2°C, pH8.05), mid-century scenario (2°C, pH7.75) and end-century scenario (2°C, pH7.54). Environmental change impacts on shell repair are rarely studied, but here repair was not affected by either acidified conditions or temperature. Growth rate was also not impacted by low pH. Elevated temperature did, however, increase growth rates. The ability of L.uva to continue, and even increase shell production in warmer and acidified seawater suggests that this species can acclimate to these combined stressors and generate suitable conditions for shell growth at the site of calcification.Emma Cross is supported by the NERC PhD Studentship (NE/T/A/2011).This is the accepted manuscript. The final version is available at http://www.sciencedirect.com/science/article/pii/S0022098114002743

Thicker Shells Compensate Extensive Dissolution in Brachiopods under Future Ocean Acidification.

Organisms with long generation times require phenotypic plasticity to survive in changing environments until genetic adaptation can be achieved. Marine calcifiers are particularly vulnerable to ocean acidification due to dissolution and a reduction in shell-building carbonate ions. Long-term experiments assess organisms' abilities to acclimatize or even adapt to environmental change. Here we present an unexpected compensatory response to extensive shell dissolution in a highly calcium-carbonate-dependent organism after long-term culture in predicted end-century acidification and warming conditions. Substantial shell dissolution with decreasing pH posed a threat to both a polar ( Liothyrella uva) and a temperate ( Calloria inconspicua) brachiopod after 7 months and 3 months exposure, respectively, with more extensive dissolution in the polar species. This impact was reflected in decreased outer primary layer thickness in the polar brachiopod. A compensatory response of increasing inner secondary layer thickness, and thereby producing a thicker shell, was exhibited by the polar species. Less extensive dissolution in the temperate brachiopod did not affect shell thickness. Increased temperature did not impact shell dissolution or thickness. Brachiopod ability to produce a thicker shell when extensive shell dissolution occurs suggests this marine calcifier has great plasticity in calcification providing insights into how similar species might cope under future environmental change

PATTERNS OF UNREPAIRED SHELL DAMAGE IN RECENT BRACHIOPODS FROM FIORDLAND (NEW ZEALAND)

In order to provide quantitative data concerning patterns of shell breakage and repair in rhynchonelliform brachiopods, we studied undisturbed death assemblages from a New Zealand fiord complex where three species of terebratulide and one rhynchonellide occur in dense mixed patches on the near vertical walls. Proportions of damaged (both repaired and non-repaired) individuals varied between both taxa and sampling site. However, the general observation was that few individuals show signs of having been able to repair damage but the proportion of individuals showing unrepaired, and hence presumably fatal, breakages was higher (up to 76% in Magasella sanguinea from one sample from Tricky Cove in Doubtful Sound). Damage was mostly concentrated around the anterior margins and affected both valves and is consistent with having been clamped between a set of either jaws or claws. Potential culprits include fish (wrasse), rock lobsters and echinoids. As yet it is unclear whether the damage results from deliberate feeding activity or as collateral damage from grazers feeding on other organisms on the fiord walls which may allow secondary predation by asteroids. The net effect is, however, the same, in that the damage appears to have been fatal. More structured sampling is now required to understand the spatial variation in this damage and mortality, and also to establish the culprits with more certainty

Structure and crystallography of foliated and chalk shell microstructures of the oyster Magallana: the same materials grown under different conditions.

Oyster shells are mainly composed of layers of foliated microstructure and lenses of chalk, a highly porous, apparently poorly organized and mechanically weak material. We performed a structural and crystallographic study of both materials, paying attention to the transitions between them. The morphology and crystallography of the laths comprising both microstructures are similar. The main differences were, in general, crystallographic orientation and texture. Whereas the foliated microstructure has a moderate sheet texture, with a defined 001 maximum, the chalk has a much weaker sheet texture, with a defined 011 maximum. This is striking because of the much more disorganized aspect of the chalk. We hypothesize that part of the unanticipated order is inherited from the foliated microstructure by means of, possibly, [Formula: see text] twinning. Growth line distribution suggests that during chalk formation, the mantle separates from the previous shell several times faster than for the foliated material. A shortage of structural material causes the chalk to become highly porous and allows crystals to reorient at a high angle to the mantle surface, with which they continue to keep contact. In conclusion, both materials are structurally similar and the differences in orientation and aspect simply result from differences in growth conditions

Institutional Repository and Archives Partnerships and Futures

A reality of dwindling resources in archives, as well as in higher education more broadly, is that the ability to purchase and maintain a specialized archives management and content management software is often out of reach. For Marshall University Special Collections, the solution to make finding aids and other digital archival materials accessible online required evaluating software already available at the university. Marshall Digital Scholar (MDS), an instance of the bepress institutional repository software, was chosen for its immediate availability, robust discovery services within the repository and through outside search engines, statistic tracking capability, metadata flexibility, support for multiple file types, and its availability to researchers on and off campus

A 120-year record of resilience to environmental change in brachiopods

The inability of organisms to cope in changing environments poses a major threat to their survival. Rising carbon dioxide concentrations, recently exceeding 400 μatm, are rapidly warming and acidifying our oceans. Current understanding of organism responses to this environmental phenomenon is based mainly on relatively short‐ to medium‐term laboratory and field experiments, which cannot evaluate the potential for long‐term acclimation and adaptation, the processes identified as most important to confer resistance. Here, we present data from a novel approach that assesses responses over a centennial timescale showing remarkable resilience to change in a species predicted to be vulnerable. Utilising museum collections allows the assessment of how organisms have coped with past environmental change. It also provides a historical reference for future climate change responses. We evaluated a unique specimen collection of a single species of brachiopod (Calloria inconspicua) collected every decade from 1900 to 2014 from one sampling site. The majority of brachiopod shell characteristics remained unchanged over the past century. One response, however, appears to reinforce their shell by constructing narrower punctae (shell perforations) and laying down more shell. This study indicates one of the most calcium‐carbonate‐dependent species globally to be highly resilient to environmental change over the last 120 years and provides a new insight for how similar species might react and possibly adapt to future change

Thicker shells compensate extensive dissolution in brachiopods under future ocean acidification

Organisms with long generation times require phenotypic plasticity to survive in changing environments until genetic adaptation can be achieved. Marine calcifiers are particularly vulnerable to ocean acidification due to dissolution and a reduction in shell-building carbonate ions. Long-term experiments assess organisms’ abilities to acclimatise or even adapt to environmental change. Here we present an unexpected compensatory response to extensive shell dissolution in a highly calcium-carbonate-dependent organism after long-term culture in predicted end-century acidification and warming conditions. Substantial shell dissolution with decreasing pH posed a threat to both a polar (Liothyrella uva) and a temperate (Calloria inconspicua) brachiopod after 7 months and 3 months exposure, respectively, with more extensive dissolution in the polar species. This impact was reflected in decreased outer primary layer thickness in the polar brachiopod. A compensatory response of increasing inner secondary layer thickness, and thereby producing a thicker shell was exhibited by the polar species. Less extensive dissolution in the temperate brachiopod did not affect shell thickness. Increased temperature did not impact shell dissolution or thickness. Brachiopod ability to produce a thicker shell when extensive shell dissolution occurs suggests this marine calcifier has great plasticity in calcification providing insights into how similar species might cope under future environmental change

Instability of a four-dimensional de Sitter black hole with a conformally coupled scalar field

We study the stability of new neutral and electrically charged four-dimensional black hole solutions of Einstein's equations with a positive cosmological constant and conformally coupled scalar field. The neutral black holes are always unstable. The charged black holes are also shown analytically to be unstable for the vast majority of the parameter space of solutions, and we argue using numerical techniques that the configurations corresponding to the remainder of the parameter space are also unstable.Comment: revtex4, 8 pages, 4 figures, minor changes, accepted for publication in Phys. Rev.