Shell Calcification Research Articles

Part II - Microstructural and Physical of Calcium Phosphate Biomaterials Obtained from Natural Raw Materials

Calcium phosphate bioceramics obtained from raw materials are potential bone substitutes in orthopedic and dental applications. Calcium phosphates attained from calcareous shells using wet methods provide an interconnected microporous framework, shown to be promising and contribute to cell adhesion and proliferation. This study aimed to characterize three different calcium phosphate ratio compositions: (i)1.4, (ii)1.6 and (iii)1.7 molar, sintered for 2 hours at 1100°C and 1200°C. Scanning electron microscopy field effect [FEG] and confocal were used to assess microstructural characterization and Arthur method to determine open porosity. FEG and confocal analyses showed good grain coalescence, sinterability and well defined interfaces for all Ca/P molar at 1100°C and 1200°C. Open porosity and hydrostatic density exhibit better results when using Ca/P molar ratio (iii)1.7 at 1100°C. The results showed that open porosity is related to Ca/P ratio and by temperature. As the Ca/P increases so does the open porosity. Inversely occurs for temperature. As the temperature increases the porosity decreases and in parallel, the grain size increases.

Part I - Sinterability of Calcium Phosphate Biomaterials Obtained from Fossilized Calcareous Shells for Biomedical Applications

Failures, infections, tumors are some bone defects causes. To repair these defects, studies show calcium phosphate bioceramics, which have been chemical and crystallographic similarity with the human bone and are biocompatible, favoring the interaction of these with vivo organisms, for bone repair. These biomaterials can be obtained from different synthesis methods. The powders, in this study, were obtained by wet method, using alternative raw material calcium carbonate from fossilized calcareous shells. The present paper aimed to elaborate and characterize different calcium phosphate ratio compositions: (i)1.4; (ii)1.6 and (iii)1.7 molar, sintered for 2 hours at 1100°C and 1200°C, further these powders were compressed in forms of cylinders. The characterization was realized by X-Ray Fluorescence (XFR), Fourier Transform Infrared Spectroscopy (FTIR) and X-ray diffractometry (XRD). The chemical and physical results shown small variations according to the Ca/P molar ratio and temperature increases.

About the Cover

Next article FreeAbout the CoverPDFPDF PLUSFull Text Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinked InRedditEmailQR Code SectionsMoreCover“Sea hares” such as the Aplysia punctata (Cuvier, 1803) specimen from Yorkshire, England, pictured on the cover, are coastal marine gastropods that have distinctive, pointed rhinophores that resemble the ears of terrestrial hares. Its congener A. californica is a model organism for neurobiology. All marine species, Aplysia included, face challenges from climate warming and ocean acidification, the process of decreasing seawater pH caused by increased levels of dissolved atmospheric CO2. One of the most prominent potential impacts of ocean acidification is that lower seawater pH will weaken calcium carbonate shells through dissolution, or increase the energy required to build and maintain them. Ocean acidification has also been shown to cause changes in the metabolic rates of many marine species, with further implications for the energetics of building and maintaining shells.On pages 142–151 of this issue, Nicholas Carey, Sam Dupont, and Julia Sigwart, in the first study of the effects of ocean acidification in sea hares, report the effects of extreme low pH on metabolism and shell calcification in A. punctata. They determined that low pH caused metabolic depression in these species, at least in the short term. But despite the low pH conditions, there was no impact on calcification in its internal shell. In the mollusc, shell growth occurs in two stages; first, a proteinaceous matrix is laid down, and then calcification occurs within this scaffolding, as long as acid-base balance is maintained by the animal. However, there was evidence that the lower metabolic rates resulted in reduced growth of the proteinaceous matrix, which would eventually result in reduced overall shell growth.The results of this work suggest that the prominence given to impacts of ocean acidification upon calcification may be overstated; the ability of marine invertebrates to maintain the proper conditions for calcification may be more common than previously thought. Calcification can occur even under extreme low pH conditions, as long as the supporting matrix is present. Instead, future studies should consider the overall impacts of ocean acidification on the energetics of calcifying organisms; impacts to shell growth may be due to energetic constraints, rather than the common perception of an acidic ocean dissolving away the shells of marine organisms.Credits: Photo, © Ian F. Smith, http://bit.ly/aplysia; cover design: LianneDunn.com Next article DetailsFiguresReferencesCited by The Biological Bulletin Volume 231, Number 2October 2016 Published in association with the Marine Biological Laboratory Article DOIhttps://doi.org/10.1086/690097 © 2016 by Marine Biological Laboratory. All rights reserved.PDF download Crossref reports no articles citing this article.

Enrichment and toxicity of trace metals in near-shore bottom sediments of Cuddalore, SE coast of India

In order to identify contaminating trace metals and their sources, studies on trace metals are often included in routine environmental monitoring programs. Twenty-five near-shore bottom sediment samples from the inner shelf region (near Cuddalore) of the Bay of Bengal were analysed for sediment texture, organic matter, carbonate (CaCO3) concentrations and total trace metal concentrations (TTMs) (Fe, Mn, Cr, Cu, Ni, Co, Pb, Zn and Cd) in order to evaluate geochemical processes such as enrichment and their origin. The presence of carbonates (2.5–5.8 %) indicates the dominance of calcareous shells in the region. A relatively high percentage of organic matter (0.2–3.9 %) is attributed to the predominance of finer sediments entering through the minor rivers. High concentrations of TTMs in fine and organic-rich sediments are influenced by municipal and industrial sources, which contention is well supported by correlations of TTMs concentrations with Fe–Mn fractions. Geoaccumulation index (Igeo) calculations indicate that Cr, Cu, Ni, Pb and Cd concentrations are above the values expected from their presence in the discharge of effluents from the industrial zones bordering the shoreline. Comparing the findings of the present study with those from different parts of the World, Cr, Cu, Ni, Pb appear to be enriched in the sediments of the region.

First proteomic analyses of the dorsal and ventral parts of the Sepia officinalis cuttlebone

Protein compounds constituting mollusk shells are known for their major roles in the biomineralization processes. These last years, a great diversity of shell proteins have been described in bivalves and gastropods allowing a better understanding of the calcification control by organic compounds and given promising applications in biotechnology. Here, we analyzed for the first time the organic matrix of the aragonitic Sepia officinalis shell, with an emphasis on protein composition of two different structures: the dorsal shield and the chambered part. Our results highlight an organic matrix mainly composed of polysaccharide, glycoprotein and protein compounds as previously described in other mollusk shells, with quantitative and qualitative differences between the dorsal shield and the chamber part. Proteomic analysis resulted in identification of only a few protein compounds underlining the lack of reference databases for Sepiidae. However, most of them contain domains previously characterized in matrix proteins of aragonitic shell-builder mollusks, suggesting ancient and conserved mechanisms of the aragonite biomineralization processes within mollusks. Biological significanceThe cuttlefish's inner shell, better known under the name “cuttlebone”, is a complex mineral structure unique in mollusks and involved in tissue support and buoyancy regulation. Although it combines useful properties as high compressive strength, high porosity and high permeability, knowledge about organic compounds involved in its building remains limited. Moreover, several cuttlebone organic matrix studies reported data very different from each other or from other mollusk shells. Thus, this study provides 1) an overview of the organization of the main mineral structures found in the S. officinalis shell, 2) a reliable baseline about its organic composition, and 3) a first descriptive proteomic approach of organic matrices found in the two main parts of this shell. These data will contribute to the general knowledge about mollusk biomineralization as well as in the identification of protein compounds involved in the Sepiidae shell calcification.

Proteomic characterization of oyster shell organic matrix proteins (OMP).

Oysters are economically and ecologically important bivalves, with its calcareous shell and delicious meat. The shell composition is a blend of inorganic crystals and shell proteins that form an organic matrix which protects the soft inner tissue of the oyster. The objective of the study was to compare the composition of organic matrix proteins (OMP) of two phylogenetically related species: the Hong Kong oyster (Crassostrea hongkongensis) and the Portuguese oyster (Crassostrea angulata) which differ in their shell hardness and mechanical properties. C. hongkongensis shells are comparatively stronger than C. angulata. Modern shotgun proteomics has been used to understand the nature of the OMP and the variations observed in the mechanical properties of these two species of oyster shells. After visualizing proteins on the one (1DE) and two-dimensional electrophoresis (2DE) gels, the protein spots and their intensities were compared using PDQuest software and 14 proteins of C. hongkongensis were found to be significantly different (student׳s t-test; p<0.05) when compared to the C. angulata. Furthermore, shell OMP separated on 1DE gels were processed using Triple TOF5600 mass spectrometry and 42 proteins of C. hongkongensis and 37 of C. angulata identified. A Circos based comparative analysis of the shell proteins of both oyster species were prepared against the shell proteome of other shell forming gastropods and molluscs to study the evolutionary conservation of OMP and their function. This comparative proteomics expanded our understating of the molecular mechanism behind the shells having different hardness and mechanical properties.

Histopathological effect and stress response of mantle proteome following TBT exposure in the Hooded oyster Saccostrea cucullata

Tributyltin (TBT), an environmental pollutant in marine ecosystems, is toxic to organisms. Although contamination by and bioaccumulation and toxicity of this compound have been widely reported, its underlying molecular mechanisms remain unclear. In the present study, we exposed the Hooded oyster Saccostrea cucullata to TBT to investigate histopathological effects and proteome stress response. Animals were exposed to three TBT sub-lethal concentrations, 10, 50 and 150 μg/l for 48 h. TBT produced stress leading to histopathological changes in oyster tissues including mantle, gill, stomach and digestive diverticula. TBT induced mucocyte production in epithelia and hemocyte aggregation in connective tissue. Cell necrosis occurred when exposure dosages were high. Comparative proteome analyses of mantle protein of oysters exposed to 10 μg/l and control animals were analyzed by a 2-DE based proteomic approach. In total, 32 protein spots were found to differ (p < 0.05). Of these, 17 proteins were identified which included 14 up-regulated and 3 down-regulated proteins. TBT induced the expression of proteins involved in defensive mechanisms (HSP-78, HSP-70, aldehyde dehydrogenase and catalase), calcium homeostasis (VDAC-3), cytoskeleton and cytoskeleton-associated proteins, energy metabolism and amino acid metabolism. Our study revealed that TBT disturbs calcium homeostasis via VDAC-3 protein in mantle and this probably is the key molecular mechanism of TBT acting to distort shell calcification. Moreover, proteins involved in cell structure (tubulin-alpha and tubulin-beta) and protein synthesis were reduced after TBT exposure. Additionally, differential proteins obtained from this work will be useful as potential TBT biomarkers.

The Effect of Paraquat (Herbicide) on the Mantle of Freshwater Snail &lt;i&gt;Lymnaea luteola&lt;/i&gt; (Lamarck:1799)

Mantle cavity act as a respiratory organ in most molluscs and is the specialized organ of the gastropods for it not only bears the glands that secrete the shell but also acts as buffer between the hard calcareous shell and the animal itself, spreading like a cushion through the entire inner surface of the body whorl. It is highly muscular, thin and bound by a single layer of epithelial cells. The present study was designed to investigate the histopathological effect of paraquat on the mantle of freshwater snail L.luteola . Acute toxicity of concentration of paraquat to L.luteola was determined by recording the snail mortality of 24,28,72 and 96 hrs exposures. The LC 50 value based on probit analysis was found to be 0.073 ml/L for 96 hrs of exposure to the herbicide. Microscopical examination of treated animals revealed severe structural alterations in the mantle of L.luteola . The glandular cells exhibited a mild to heavy bioaccumulation of the herbicide which was a time dependent effect. At various concentrations paraquat causes significant dose dependent changes such as : desquamation of epithelial cell, atrophy of muscle fibers, necrosis, in respect of glandular cells.

The usability of ark clam shell (Anadara granosa) as calcium precursor to produce hydroxyapatite nanoparticle via wet chemical precipitate method in various sintering temperature.

This paper reported the uses of ark clam shell calcium precursor in order to form hydroxyapatite (HA) via the wet chemical precipitation method. The main objective of this research is to acquire better understanding regarding the effect of sintering temperature in the fabrication of HA. Throughout experiment, the ratio of Ca:P were constantly controlled, between 1.67 and 2.00. The formation of HA at these ratio was confirmed by means of energy-dispersive X-ray spectroscopy analysis. In addition, the effect of sintering temperature on the formation of HA was observed using X-ray diffraction analysis, while the structural and morphology was determined by means of field emission scanning electron microscopy. The formation of HA nanoparticle was recorded (~35–69 nm) in the form of as-synthesize HA powder. The bonding compound appeared in the formation of HA was carried out using Fourier transform infrared spectroscopy such as biomaterials that are expected to find potential applications in orthopedic and biomedical industries .

Genetic architecture dissection by genome-wide association analysis reveals avian eggshell ultrastructure traits.

The ultrastructure of an eggshell is considered the major determinant of eggshell quality, which has biological and economic significance for the avian and poultry industries. However, the interrelationships and genome-wide architecture of eggshell ultrastructure remain to be elucidated. Herein, we measured eggshell thickness (EST), effective layer thickness (ET), mammillary layer thickness (MT), and mammillary density (MD) and conducted genome-wide association studies in 927 F2 hens. The SNP-based heritabilities of eggshell ultrastructure traits were estimated to be 0.39, 0.36, 0.17 and 0.19 for EST, ET, MT and MD, respectively, and a total of 719, 784, 1 and 10 genome-wide significant SNPs were associated with EST, ET, MT and MD, respectively. ABCC9, ITPR2, KCNJ8 and WNK1, which are involved in ion transport, were suggested to be the key genes regulating EST and ET. ITM2C and KNDC1 likely affect MT and MD, respectively. Additionally, there were linear relationships between the chromosome lengths and the variance explained per chromosome for EST (R2 = 0.57) and ET (R2 = 0.67). In conclusion, the interrelationships and genetic architecture of eggshell ultrastructure traits revealed in this study are valuable for our understanding of the avian eggshell and contribute to research on a variety of other calcified shells.

Intraspecific variations in shell calcification across thermal window and within constant temperatures: Experimental study on an intertidal gastropod Monetaria annulus

The relationship between temperature and shell growth was examined by rearing an intertidal cowrie species, Monetaria annulus (Gastropoda, Cypraeidae), at seven constant temperatures between 21°C and 34°C over four experimental years. Data on shell growth were collected during the callus-building stage, in which calcification exclusively occurs around the spiral shell constructed in the juvenile stage. Our experiments elucidated some clear trends among temperatures, although careful consideration is required to interpret the results obtained under the potential confounding factors between temperature and experimental year. Calcification was accelerated by increasing temperature in the range between 21°C and 33°C, and drastically slowed down at 34°C probably due to heat stress. No relationship was found between body size and callus growth rates. The duration of callus-building indicated a negative exponential relationship with rearing temperature. However, no simple relationship was found between temperature and final shell thickness; the final shell thickness described two peaks around 21°C and 30°C. This finding strongly suggests that a physiological control by calcifiers cannot be ignored to explain the thermal response of calcification rates. Our results also suggest that considering the thermal seasonality as well as the difference in mean temperature, is required to explain the negative latitudinal clines in shell thickness frequently observed in molluscan species. We also focused on the variation among the individuals reared at the same temperatures. Statistical analyses suggested that the final shell thickness and the duration of calcification were better described by the normal and lognormal distributions, respectively. The distribution of shell growth rates did not considerably deviate from the normal distribution with respect to skewness and kurtosis. However, their heteroscedasticity among temperatures was inherent and significant; its variance positively depended not on the mean but on temperature. The observed pattern might be an evidence that possible stabilization selection on calcification rates is more relaxed at warmer temperatures.

Dependency of the optical properties of heterogeneous calcium bismuthate–bismuth oxide particles on the order of layers alternation

This paper provides the research data devoted to the influence of photocatalyst production method as the heterogeneous structure of calcium bismuthate–bismuth oxide on its optical and catalytic properties. Two method of photocatalyst production were researched in “core–shell” type. In the first method the core is bismuth oxide, and the shell–calcium bismuthate. The second method uses the reversed sequence of abovementioned layers. It is specified that the quantitative and spectrum properties of the absorbed radiation are dependent on the sequence of the core and shell layers in the photocatalyst particles.

Historical baselines and the future of shell calcification for a foundation species in a changing ocean.

Seawater pH and the availability of carbonate ions are decreasing due to anthropogenic carbon dioxide emissions, posing challenges for calcifying marine species. Marine mussels are of particular concern given their role as foundation species worldwide. Here, we document shell growth and calcification patterns in Mytilus californianus, the California mussel, over millennial and decadal scales. By comparing shell thickness across the largest modern shells, the largest mussels collected in the 1960s-1970s and shells from two Native American midden sites (∼1000-2420 years BP), we found that modern shells are thinner overall, thinner per age category and thinner per unit length. Thus, the largest individuals of this species are calcifying less now than in the past. Comparisons of shell thickness in smaller individuals over the past 10-40 years, however, do not show significant shell thinning. Given our sampling strategy, these results are unlikely to simply reflect within-site variability or preservation effects. Review of environmental and biotic drivers known to affect shell calcification suggests declining ocean pH as a likely explanation for the observed shell thinning. Further future decreases in shell thickness could have significant negative impacts on M. californianus survival and, in turn, negatively impact the species-rich complex that occupies mussel beds.

The Shell of the Invasive Bivalve Species Dreissena polymorpha: Biochemical, Elemental and Textural Investigations.

The zebra mussel Dreissena polymorpha is a well-established invasive model organism. Although extensively used in environmental sciences, virtually nothing is known of the molecular process of its shell calcification. By describing the microstructure, geochemistry and biochemistry/proteomics of the shell, the present study aims at promoting this species as a model organism in biomineralization studies, in order to establish a bridge with ecotoxicology, while sketching evolutionary conclusions. The shell of D. polymorpha exhibits the classical crossed-lamellar/complex crossed lamellar combination found in several heterodont bivalves, in addition to an external thin layer, the characteristics of which differ from what was described in earlier publication. We show that the shell selectively concentrates some heavy metals, in particular uranium, which predisposes D. polymorpha to local bioremediation of this pollutant. We establish the biochemical signature of the shell matrix, demonstrating that it interacts with the in vitro precipitation of calcium carbonate and inhibits calcium carbonate crystal formation, but these two properties are not strongly expressed. This matrix, although overall weakly glycosylated, contains a set of putatively calcium-binding proteins and a set of acidic sulphated proteins. 2D-gels reveal more than fifty proteins, twenty of which we identify by MS-MS analysis. We tentatively link the shell protein profile of D. polymorpha and the peculiar recent evolution of this invasive species of Ponto-Caspian origin, which has spread all across Europe in the last three centuries.

Characterization of the mantle transcriptome in bivalves: Pecten maximus, Mytilus edulis and Crassostrea gigas

The calcareous shells secreted by bivalve molluscs display diverse and species specific structural compositions, which indicates possible divergent biomineralization processes. Thus, studying multiple mollusc species will provide a more comprehensive understanding of shell formation. Here, the transcriptomes of the mantle tissues responsible for shell deposition were characterized in three commercially relevant bivalve species. Using high-throughput sequencing and bioinformatics tools, de novo transcriptome assemblies of mantle tissues were generated for the mussel Mytilus edulis, the oyster Crassostrea gigas and the scallop Pecten maximus. These transcriptomes were annotated, and contigs with similarity to proteins known to have shell formation roles in other species were identified. Comparison of the shell formation specific proteins in the three bivalves indicates the possibility of species specific shell proteins.

Benefits of Zubex beyond glycemic control: Evidence of the antiatherogenic effect.

To determine the effect of Zubex (aqueous extract of Curcuma longa linn, Iron murakab, Eugenia jambolana, Lin seed or flflax seed, processed egg shell calcium and Asphaltum) on plasma sialic acid (PSA) along with cardiovascular (CV) risk factors in streptozotocin-induced diabetic rats. Thirty male albino rats were divided into groups (1-6) with 5 rats in each group. Group 1 and 2 served as normal control (NC) and diabetic control (DC), respectively, and were given normal saline only. Groups 3-5 were given Zubex in different doses 100-400 mg/(kg day). Group 6 received glibenclamide 600 μg/(kg day) orally as a reference drug. Fasting plasma glucose (FPG) and PSA levels were determined at baseline after every 2 weeks for 10 weeks. The other parameters including blood lipids and hepatic enzymes were determined at baseline and at the end of the study. Finally, the liver was subjected to histological examination. Compared with DC group, Zubex treated groups showed signifificant decline in FPG levels (P<0.05). At the endpoint, the decrease in PSA concentration was significant (P<0.05) from baseline at the doses of 200 and 400 mg/(kg day) only and insignifificant at the dose of 100 mg/ (kg day). Statistically signifificant improvements were observed in blood lipids at the doses of 200 and 400 mg/kg (P<0.05) compared with DC; but, the improvement was insignifificant in low density lipoprotein-cholesterol and high density lipoprotein-cholesterol at the dose of 100 mg/ (kg day). Signifificant decreases were also found in hepatic enzyme levels at all the doses of Zubex (P<0.05). Histological examination showed marked improvement in streptozotocin induced liver injury after treatment of all the 3 doses of Zubex. Zubex could ameliorate PSA and other diabetic complications effectively and may be a useful alternative/adjuvant in diabetes treatment.

Effect of Turmeric Powder Supplementation to The Age of Sexual Maturity, Physical, and Chemical Quality of The First Japanese Quail’s (Coturnix japonica) Egg

&lt;p&gt;The experiment was conducted to determine the effect of turmeric powder supplementation to the age of sexual maturity, physical, and chemical quality of the first Japanese quail’s (Coturnix japonica) egg. Forty five quails were assigned into a completely randomized design with three treatments (levels of turmeric powder, i.e., 0; 54; and 108 mg/quail/day) and each treatment used 15 quails. Turmeric powder supplementation was conducted before sexual maturity. Feed and drinking water provided ad libitum. Observed egg is an egg that was first produced. Parameters measured were the age of sexual maturity, feed intake, body weight, physical qualities which include: weight of egg, long axis, short axis, weight and thickness of shell, yolk index, Haugh unit, egg shell index. Whereas the observed chemical quality were cholesterol, HDL, LDL, protein, vitamin B12, vitamin A in eggs and egg shell calcium levels. The results showed that administration of turmeric powder can accelerate the age of maturity, increasing the levels of protein, HDL, vitamin A and B12 in eggs, decreasing the cholesterol and LDL content in eggs, but did not affect feed intake, physical quality of eggs and egg shell calcium levels. Based on the results of this study, it can be concluded that supplementation of turmeric powder improve the chemical quality of Japanese quail eggs (Coturnix japonica), so it is good for the development of quail embryos as well as for consumption.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;How to Cite&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;Saraswati, T. R., &amp;amp; Tana, S. (2016). Effect of Turmeric Powder Supplementation To The Age of Sexual Maturity, Physical, and Chemical Quality of The First Japanese Quail’s (Coturnix japonica) Egg. &lt;em&gt;Biosaintifika: Journal of Biology &amp;amp; Biology Education&lt;/em&gt;, 8(1), 18-24.&lt;/p&gt;

GIANTS AMONG MICROMORPHS: WERE CINCINNATIAN (ORDOVICIAN, KATIAN) SMALL SHELLY PHOSPHATIC FAUNAS DWARFED?

Abstract Small fossils are preserved as phosphatic (carbonate fluorapatite) micro-steinkerns (~ 0.5 mm diameter) in Upper Ordovician beds of the Cincinnati area. Mollusks are common, along with bryozoan zooecia, echinoderm ossicles, and other taxa. Similar occurrences of Ordovician micromorphic mollusks have been interpreted as ecologically dwarfed and adapted to oxygen-starved conditions, an interpretation with implications for ocean anoxia. An alternative explanation for small phosphatic steinkerns is taphonomic. Stable carbonate fluorapatite selectively filled small voids, thus preserving small fossils, including larval/young mollusks. Reworking concentrated small phosphatic steinkerns from multiple generations while larger, unfilled calcareous shells were destroyed, resulting in small fossils progressively replacing larger fossils. With thin sections and insoluble residues, we document evidence that many of these steinkerns are incomplete (“teilsteinkerns”) recording small parts of larger, normal-size...

Allometric size-scaling of biometric growth parameters and metabolic and excretion rates. A comparative study of intertidal and subtidal populations of mussels (Mytilus galloprovincialis)

Allometric relationships between biometric parameters (i.e., soft body and shell weights and shell organic content vs. shell length) as well as for routine and standard metabolic and ammonia excretion rates related to flesh weight and shell length were estimated and compared for subtidal and intertidal populations of Mytilus galloprovincialis in Galicia (NW Spain). This is the first report on allometric size-scaling of excretion and metabolic (both routine and standard) rates in this species. No evidences of differences in size exponent were found between physiological rates or between both populations for any physiological rate. Intercepts of regression lines were significantly higher in subtidal than in intertidal mussels, indicating greater levels of energy expenditure in the former. However, metabolic scope for feeding and growth was about two-fold in intertidal mussels, pointing to a reduced growth efficiency compared with subtidal mussels. Evolution of biometric parameters of body components with size indicated that subtidal mussels allocated energy resources preferably into flesh growth, achieving higher condition indices, while intertidal mussels put more effort on shell calcification and thickening which resulted in heavier shells of reduced organic content. These differentiated growth “strategies” of both populations could be related to their differences in growth efficiencies.

Seasonal Variation in Shell Calcification of Planktonic Foraminifera in the NE Atlantic Reveals Species-Specific Response to Temperature, Productivity, and Optimum Growth Conditions.

Using shells collected from a sediment trap series in the Madeira Basin, we investigate the effects of seasonal variation of temperature, productivity, and optimum growth conditions on calcification in three species of planktonic Foraminifera. The series covers an entire seasonal cycle and reflects conditions at the edge of the distribution of the studied species, manifesting more suitable growth conditions during different parts of the year. The seasonal variation in seawater carbonate saturation at the studied site is negligible compared to other oceanic regions, allowing us to assess the effect of parameters other than carbonate saturation. Shell calcification is quantified using weight and size of individual shells. The size–weight scaling within each species is robust against changes in environmental parameters, but differs among species. An analysis of the variation in calcification intensity (size-normalized weight) reveals species-specific response patterns. In Globigerinoides ruber (white) and Globigerinoides elongatus, calcification intensity is correlated with temperature (positive) and productivity (negative), whilst in Globigerina bulloides no environmental forcing is observed. The size–weight scaling, calcification intensity, and response of calcification intensity to environmental change differed between G. ruber (white) and G. elongatus, implying that patterns extracted from pooled analyses of these species may reflect their changing proportions in the samples. Using shell flux as a measure of optimum growth conditions, we observe significant positive correlation with calcification intensity in G. elongatus, but negative correlation in G. bulloides. The lack of a consistent response of calcification intensity to optimum growth conditions is mirrored by the results of shell size analyses. We conclude that calcification intensity in planktonic Foraminifera is affected by factors other than carbonate saturation. These factors include temperature, productivity, and optimum growth conditions, but the strength and sign of the relationships differ among species, potentially complicating interpretations of calcification data from the fossil record.