Evaluation of radiography,ultrasonography and endoscopy for detection of shell lesions in live abalone Haliotis iris (Mollusca: Gastropoda)

Radiography, ultrasonography and endoscopy were examined for their efficacy as non-destructive techniques for the detection of shell lesions in the marine gastropod Haliotis iris Gmelin. X-rays provided 69% correct diagnoses, with detection being restricted to those lesions which were mineralised. Ultrasound also showed potential to reliably detect lesions (83% correct diagnoses), but only where the lesions demonstrated a clear 3-dimensional relief. Lesion dimensions were underestimated using ultrasound. Endoscopy, applied to anaesthetised individuals, provided the most accurate method (92% correct diagnoses) for lesion detection and, although invasive, had no discernible effect on survival of the abalone 8 mo after screening.     

Hiatal shell concentrations, sequence analysis, and sealevel history of a Pleistocene coastal alluvial fan, Punta Chueca, Sonora

Richly fossiliferous marine sediments exposed along the Sonoran coastline of the Gulf of California near Punta Chueca provide an excellent setting in which to test (a) the strength of the association of skeletal concentrations with sedimentary hiatuses, (b) the utility of taphonomic evidence for reconstructing detailed histories of those non-depositional episodes, and thus (c) the largely unexploited potential of skeletal concentrations in the identification and interpretation of lithologically obscure unconformities and condensed sequences in shallow marine deposits. Sequence analysis based on discontinuity surfaces is possible in the complex, alluvial fan-to-shallow marine transition at Punta Chueca despite rapid facies changes. Progradation of depositional sequences that contain cobbles reworked from older terrace deposits indicates accumulation during a fall in eustatic sea level. The supratidal to subtidal conglomerates and sands contain a variety of predominantly molluscan shell concentrations that, on the basis of postmortem histories of shells, formed during periods of low net sedimentation (i.e. depositional hiatuses); the majority of these shell beds lie along discontinuity surfaces identified by independent physical stratigraphic evidence. Although not all discontinuity surfaces in the terrace are paved by shell material. and not all relative concentrations of shells indicate distinct discontinuities, the strength of the association between skeletal concentrations and stratigraphic hiatuses reveals the high degree of control on fossil occurrence by sedimentation rates, and indicates that skeletal concentrations can provide good clues to stratigraphically significant surfaces. Moreover, the detailed dynamics of non-depositional episodes are reliably revealed by taphonomic analysis of the associated fossil assemblages, improving interpretations of non-depositional episodes in local sedimentary history.     

瘤棘砂壳虫(肉足亚门:根足总纲)壳体元素组成

利用X射线能谱仪对采自中国湖北省木兰湖的瘤棘砂壳虫(Diffugia tuberspinifera)壳体元素组成进行分析,结果发现：构成壳体的化学元素主要为Si,其次是Ca和Al,还有微量K、Na、Cl、Fe、Mg、S和P。分析表明瘤棘砂壳虫壳体化学元素的构成介于海洋和土壤有壳肉足虫之间。     

Detection of invasive and cryptic species in marine mussels (Bivalvia,Mytilidae): A chromosomal perspective

Marine mussels illustrate a stunning variability in shape and color. Such variability, added to the scarcity of reliable morphological characters for their identification, can mislead recognition prompting the assignation of specimens of a single species to different ones or incorporate specimens belonging to different taxa into a single one. DNA barcoding is widely used for species identification; however, as this method relies on the previous morphological identification of the specimens, some of the DNA sequences stored in DNA databases are incorrectly assigned to a given species. In view of this uncertainty, further criteria beyond morphological characters and DNA sequences in databases are required to more reliably and accurately identify marine mussels. In this work we mapped ribosomal RNA and histone gene clusters to chromosomes of four species of marine mussels and compared them with those from another eight marine mussel taxa. Specimens of these twelve taxa were also DNA barcoded. Our results clearly demonstrated that the chromosomal analysis of marine mussels could shed light on their identification and, therefore, solve contradictions posed by morphological and molecular data.     

Triangular gold nanoparticles modify shell characteristics and increase antioxidant enzyme activities in the clam Ruditapes decussatus

Context: Nanoparticles may cause adverse environmental effects but there is limited information on their interactions with marine organisms.

Objective: Our aim was to examine the effects of triangular gold nanoparticles (Tr-Au NPs) on the clam, Ruditapes decussatus.

Materials and methods: Clams were exposed to Tr-Au1?=?5?µg/L and Tr-Au2?=?10?µg/L for 2 and 7?days. Effects on shell structure were investigated. Superoxide dismutase (SOD), catalase (CAT), glutathione transferase (GST) activities, protein carbonyl levels and malondialdehyde content were used to assess biochemical status.

Results: Transmission electron microscopy (TEM) and electron dispersive X-ray microanalysis (EDX) showed that Tr-Au NPs modified shell structure and morphology. Tr-Au NPs size increased forming aggregate particles. Tr-Au NPs increased SOD, CAT and GST activities in gill and digestive gland in a concentration- and time-dependent manner indicating defence against oxidative stress. Enhanced lipid peroxidation and protein carbonyl levels confirmed oxidative stress.

Conclusion: Tr-Au NPs cause oxidative stress and affect shell structure of clams. These findings may have relevance to other marine species.     

Study of fossil and recent brachiopods,using a skyscan 1172 X-ray microtomograph

Fossil and recent brachiopods were studied with the aid of a Skyscan 1172 microtomograph. The capabilities of this method at different stages of studying, X-ray scanning and producing slices and 3D models are described. The method enables the study of punctuation, microornamentation, and inner structures of the brachiopod shells and soft tissues. The contrast of shell structures of fossil brachiopods is discussed; it depends on differences in the mineral composition of the shell and surrounding matter. This method allows studying the inner structure of the holotypes of brachiopod species without damaging their shells. The data on the efficiency of the method are provided.     

Experimental tumbling of <Emphasis Type="Italic">Dreissena polymorpha</Emphasis>: implications for recognizing durophagous predation in the fossil record

Shell damage left by predators constitutes an important source of information on predator–prey interactions. However, recognition of the origins of shell damage can often be controversial, and needs to be assessed cautiously. More specifically, differentiation between predation- and abiotic-induced shell damage remains challenging. Here, we show the results of tumbling experiments using a bivalve species Dreissena polymorpha in order to determine rates and patterns of shell damage induced by physical forces in high-energy conditions. It is demonstrated that, in contrast to durophagous fish and crab predation, abiotic-induced fragmentation and damage are typically characterized by the presence of distinct abrasive scratches and wear scars on the surface of shell fragments. Furthermore, fragmented shells typically reveal a wide size distribution, and a different degree of sphericity and roundness resulting from abrasion. Importantly, large shell fragments commonly display smooth edges. These data suggest that durophagous predation, which typically induces fragmentation into large and angular shell fragments bearing no wear scars, can be reliably recognized both in present-day environments and in the fossil record.     

Marine ash‐products influence growth and feed utilization when Atlantic cod Gadus morhua L. are fed plant‐based diets

Atlantic cod Gadus morhua L. were fed high plant protein diets added to either shrimp‐shell meal or crab‐shell meal. The aims were to investigate if diluting dietary energy would reduce the liver index (HSI) and if marine ash would add value to plant protein‐based diets. Two control diets were used: a high plant protein control diet (PP) with no marine ash addition, and a fishmeal‐based diet (FM) with no marine ash addition. All diets were evaluated in small cod (initial weight 79 ± 15g) and in market‐size cod (initial weight 1579 ± 20 g). Addition of crab‐shell meal up to 20% and shrimp‐shell meal up to 10% did not influence liver size in either small or market‐size cod. An addition of up to 20% crab‐shell meal and 10% shrimp‐shell meal improved growth compared to the PP control diet, and stimulated increased feed intake. However, 10% shrimp‐shell meal and 20% crab‐shell meal diets resulted in a similar intake of energy and protein as the control groups. Increasing shrimp‐shell meal to 20% resulted in reductions in feed intake, fat digestibility and growth, and in altered gut histology. All diets, except the 20% shrimp added diet, resulted in normal ranges of plasma nutrients and blood hematological values, showing good fish health with or without the marine ash addition.     

Predicting evolutionary responses to climate change in the sea

An increasing number of short‐term experimental studies show significant effects of projected ocean warming and ocean acidification on the performance on marine organisms. Yet, it remains unclear if we can reliably predict the impact of climate change on marine populations and ecosystems, because we lack sufficient understanding of the capacity for marine organisms to adapt to rapid climate change. In this review, we emphasise why an evolutionary perspective is crucial to understanding climate change impacts in the sea and examine the approaches that may be useful for addressing this challenge. We first consider what the geological record and present‐day analogues of future climate conditions can tell us about the potential for adaptation to climate change. We also examine evidence that phenotypic plasticity may assist marine species to persist in a rapidly changing climate. We then outline the various experimental approaches that can be used to estimate evolutionary potential, focusing on molecular tools, quantitative genetics, and experimental evolution, and we describe the benefits of combining different approaches to gain a deeper understanding of evolutionary potential. Our goal is to provide a platform for future research addressing the evolutionary potential for marine organisms to cope with climate change.     

Imaging Liver Lesions Using Grating-Based Phase-Contrast Computed Tomography with Bi-Lateral Filter Post-Processing

X-ray phase-contrast imaging shows improved soft-tissue contrast compared to standard absorption-based X-ray imaging. Especially the grating-based method seems to be one promising candidate for clinical implementation due to its extendibility to standard laboratory X-ray sources. Therefore the purpose of our study was to evaluate the potential of grating-based phase-contrast computed tomography in combination with a novel bi-lateral denoising method for imaging of focal liver lesions in an ex vivo feasibility study. Our study shows that grating-based phase-contrast CT (PCCT) significantly increases the soft-tissue contrast in the ex vivo liver specimens. Combining the information of both signals – absorption and phase-contrast – the bi-lateral filtering leads to an improvement of lesion detectability and higher contrast-to-noise ratios. The normal and the pathological tissue can be clearly delineated and even internal structures of the pathological tissue can be visualized, being invisible in the absorption-based CT alone. Histopathology confirmed the presence of the corresponding findings in the analyzed tissue. The results give strong evidence for a sufficiently high contrast for different liver lesions using non-contrast-enhanced PCCT. Thus, ex vivo imaging of liver lesions is possible with a polychromatic X-ray source and at a spatial resolution of ∼100 µm. The post-processing with the novel bi-lateral denoising method improves the image quality by combining the information from the absorption and the phase-contrast images.     

Lesion bacterial communities in American lobsters with diet-induced shell disease

In southern New England, USA, shell disease affects the profitability of the American lobster Homarus americanus fishery. In laboratory trials using juvenile lobsters, exclusive feeding of herring Clupea harengus induces shell disease typified initially by small melanized spots that progress into distinct lesions. Amongst a cohabitated, but segregated, cohort of 11 juvenile lobsters fed exclusively herring, bacterial communities colonizing spots and lesions were investigated by denaturing gradient gel electrophoresis of 16S rDNA amplified using 1 group-specific and 2 universal primer sets. The Bacteroidetes and Proteobacteria predominated in both spots and lesions and included members of the orders Flavobacteriales (Bacteriodetes), Rhodobacterales, Rhodospirillales and Rhizobiales (Alphaproteobacteria), Xanthomonadales (Gammaproteobacteria) and unclassified Gammaproteobacteria. Bacterial communities in spot lesions displayed more diversity than communities with larger (older) lesions, indicating that the lesion communities stabilize over time. At least 8 bacterial types persisted as lesions developed from spots. Aquimarina 'homaria', a species commonly cultured from lesions present on wild lobsters with epizootic shell disease, was found ubiquitously in spots and lesions, as was the 'Candidatus Kopriimonas aquarianus', implicating putative roles of these species in diet-induced shell disease of captive lobsters.     

Studying biomolecular complexes with pulsed electron-electron double resonance spectroscopy

The function of biomolecules is intrinsically linked to their structure and the complexes they form during function. Techniques for the determination of structures and dynamics of these nanometre assemblies are therefore important for an understanding on the molecular level. PELDOR (pulsed electron-electron double resonance) is a pulsed EPR method that can be used to reliably and precisely measure distances in the range 1.5-8?nm, to unravel orientations and to determine the number of monomers in complexes. In conjunction with site-directed spin labelling, it can be applied to biomolecules of all sizes in aqueous solutions or membranes. PELDOR is therefore complementary to the methods of X-ray crystallography, NMR and FRET (fluorescence resonance energy transfer) and is becoming a powerful method for structural determination of biomolecules. In the present review, the methods of PELDOR are discussed and examples where PELDOR has been used to obtain structural information on biomolecules are summarized.     

What can aquatic gastropods tell us about phenotypic plasticity? A review and meta-analysis

There have been few attempts to synthesise the growing body of literature on phenotypic plasticity to reveal patterns and generalities about the extent and magnitude of plastic responses. Here, we conduct a review and meta-analysis of published literature on phenotypic plasticity in aquatic (marine and freshwater) gastropods, a common system for studying plasticity. We identified 96 studies, using pre-determined search terms, published between 1985 and November 2013. The literature was dominated by studies of predator-induced shell form, snail growth rates and life history parameters of a few model taxa, accounting for 67% of all studies reviewed. Meta-analyses indicated average plastic responses in shell thickness, shell shape, and growth and fecundity of freshwater species was at least three times larger than in marine species. Within marine gastropods, species with planktonic development had similar average plastic responses to species with benthic development. We discuss these findings in the context of the role of costs and limits of phenotypic plasticity and environmental heterogeneity as important constraints on the evolution of plasticity. We also consider potential publication biases and discuss areas for future research, indicating well-studied areas and important knowledge gaps.     

Some morphological adaptations in freshwater bivalves

Savazzi, E. & Yao, P. 1992 04 15: Some morphological adaptations in freshwater bivalves. Lethaia , Vol. 25, pp. 195–209. Oslo. ISSN 0024–1164.
Several freshwater bivalves possess peculiar shell morphologies. An extension of the postero-dorsal shell margins above the hinge line evolved convergently in several unionids. This extension supplements the opening momentum of the ligament, but must be broken off periodically in order to allow further shell growth. Arconaia and Cuneopsis have evolved twisted commissure planes, comparable to those found in unrelated marine bivalves. In marine forms, byssus is believed to have played a fundamental role in the evolution of shell torsion. However, the twisted Unionidae do not possess a byssus in the adult stage, thus forcing us to re-evaluate our ideas on the adaptive value and evolution of shell torsion. Solenaia oleivora is apparently incapable of reburrowing and of retracting its foot within the shell. The foot may be functional as an anchor, and is perhaps involved in chemosynthesis by storing sulphur extracted as sulphide from the surrounding sediment. Other adaptations of freshwater bivalves include selective thickening of portions of the shell that enhance its stability, permanent anterior and posterior gapes, and oyster-like morphologies and shell structures. * Functional morphology, constructional morphology, burrowing, shell torsion, Mollusca, Bivalvia, Unionacea, Recent, Quaternary, People's Republic of China .     

Elevated CO2 affects shell dissolution rate but not calcification rate in a marine snail

As CO₂ levels increase in the atmosphere, so too do they in the sea. Although direct effects of moderately elevated CO₂ in sea water may be of little consequence, indirect effects may be profound. For example, lowered pH and calcium carbonate saturation states may influence both deposition and dissolution rates of mineralized skeletons in many marine organisms. The relative impact of elevated CO₂ on deposition and dissolution rates are not known for many large-bodied organisms. We therefore tested the effects of increased CO₂ levels—those forecast to occur in roughly 100 and 200 years—on both shell deposition rate and shell dissolution rate in a rocky intertidal snail, Nucella lamellosa. Shell weight gain per day in live snails decreased linearly with increasing CO₂ levels. However, this trend was paralleled by shell weight loss per day in empty shells, suggesting that these declines in shell weight gain observed in live snails were due to increased dissolution of existing shell material, rather than reduced production of new shell material. Ocean acidification may therefore have a greater effect on shell dissolution than on shell deposition, at least in temperate marine molluscs.     

SHELL MICROSTRUCTURE OF GASTROPODS FROM LAKE TANGANYIKA,AFRICA: ADAPTATION,CONVERGENT EVOLUTION,AND ESCALATION

Gastropod shells from Lake Tanganyika, with their heavy calcification, coarse noded ribbing, spines, apertural lip thickening and repair scars, resemble marine shells more closely than they resemble other lacustrine shells. This convergence between Tanganyikan and marine gastropod shells, however, is not just superficial. Scanning electron microscope (SEM) studies reveal that the Tanganyikan shells are primarily layers of crossed-lamellar crystal architecture (that is, needle-like aragonite crystals arranged into laths that are packed into sheets such that the aragonite needles of adjacent laths are never parallel). The number of crossed-lamellar layers can vary from one to four between different Tanganyikan gastropod species. In species with two or more crossed-lamellar layers, the orientation of the lamellae is offset by approximately 90° between the different layers. The number of crossed-lamellar layers in the shell wall is positively correlated with shell strength and with predation resistance. Three and four crossed-lamellar layers in the shell wall evolved several times independently within the endemic thiarid gastropod radiation in Lake Tanganyika. Repeated origins of three and four crossed-lamellar layers suggest that they may be specific adaptations by Tanganyikan gastropods to strengthen their shells as a defense against shell-crushing predators.     

Ancient DNA analysis identifies marine mollusc shells as new metagenomic archives of the past

Marine mollusc shells enclose a wealth of information on coastal organisms and their environment. Their life history traits as well as (palaeo‐) environmental conditions, including temperature, food availability, salinity and pollution, can be traced through the analysis of their shell (micro‐) structure and biogeochemical composition. Adding to this list, the DNA entrapped in shell carbonate biominerals potentially offers a novel and complementary proxy both for reconstructing palaeoenvironments and tracking mollusc evolutionary trajectories. Here, we assess this potential by applying DNA extraction, high‐throughput shotgun DNA sequencing and metagenomic analyses to marine mollusc shells spanning the last ~7,000 years. We report successful DNA extraction from shells, including a variety of ancient specimens, and find that DNA recovery is highly dependent on their biomineral structure, carbonate layer preservation and disease state. We demonstrate positive taxonomic identification of mollusc species using a combination of mitochondrial DNA genomes, barcodes, genome‐scale data and metagenomic approaches. We also find shell biominerals to contain a diversity of microbial DNA from the marine environment. Finally, we reconstruct genomic sequences of organisms closely related to the Vibrio tapetis bacteria from Manila clam shells previously diagnosed with Brown Ring Disease. Our results reveal marine mollusc shells as novel genetic archives of the past, which opens new perspectives in ancient DNA research, with the potential to reconstruct the evolutionary history of molluscs, microbial communities and pathogens in the face of environmental changes. Other future applications include conservation of endangered mollusc species and aquaculture management.     

A New Approach for the Determination of Ammonite and Nautilid Habitats

Externally shelled cephalopods were important elements in open marine habitats throughout Earth history. Paleotemperatures calculated on the basis of the oxygen isotope composition of their shells can provide insights into ancient marine systems as well as the ecology of this important group of organisms. In some sedimentary deposits, however, the aragonitic shell of the ammonite or nautilid is poorly or not preserved at all, while the calcitic structures belonging to the jaws are present. This study tests for the first time if the calcitic jaw structures in fossil cephalopods can be used as a proxy for paleotemperature. We first analyzed the calcitic structures on the jaws of Recent Nautilus and compared the calculated temperatures of precipitation with those from the aragonitic shell in the same individuals. Our results indicate that the jaws of Recent Nautilus are secreted in isotopic equilibrium, and the calculated temperatures approximately match those of the shell. We then extended our study to ammonites from the Upper Cretaceous (Campanian) Pierre Shale of the U.S. Western Interior and the age-equivalent Mooreville Chalk of the Gulf Coastal Plain. In the Pierre Shale, jaws occur in situ inside the body chambers of well-preserved Baculites while in the Mooreville Chalk, the jaw elements appear as isolated occurrences in the sediment and the aragonitic shell material is not preserved. For the Pierre Shale specimens, the calculated temperatures of well-preserved jaw material match those of well-preserved shell material in the same individual. Analyses of the jaw elements in the Mooreville Chalk permit a comparison of the paleotemperatures between the two sites, and show that the Western Interior is warmer than the Gulf Coast at that time. In summary, our data indicate that the calcitic jaw elements of cephalopods can provide a reliable geochemical archive of the habitat of fossil forms.     

A Method for Cytogenetic and Cytological Examination of Small Shelled Larvae of Bivalves and Other Zooplankton

Studies on chromosomes and nuclei of very small bivalve larvae have been impeded by the veliger shell. It has been determined that the alcohokacetic acid fixative commonly used in cytogenetic techniques can be made to act as a decalcifying agent upon repeated heating. In addition, transfer of formalin fixed shelled specimens, routinely used as marine bioassay organisms, into ethyl alcohohacetic acid (3:1) fixative also yields clear cells for cytological examination of decalcified but otherwise intact oyster larvae and other zoo-plankton. Identification of cell type, such as germ-line primordia, in, for example, reproductive and ploidy level studies, and observations on the presence of bacteria can be made from the preparations. Material can be examined up to at least a year after preservation. The method is evaluated and its modifications are discussed.