Shell Mineralization Research Articles

Hen uterine gene expression profiling during eggshell formation reveals putative proteins involved in the supply of minerals or in the shell mineralization process.

BackgroundThe chicken eggshell is a natural mechanical barrier to protect egg components from physical damage and microbial penetration. Its integrity and strength is critical for the development of the embryo or to ensure for consumers a table egg free of pathogens. This study compared global gene expression in laying hen uterus in the presence or absence of shell calcification in order to characterize gene products involved in the supply of minerals and / or the shell biomineralization process.ResultsMicroarrays were used to identify a repertoire of 302 over-expressed genes during shell calcification. GO terms enrichment was performed to provide a global interpretation of the functions of the over-expressed genes, and revealed that the most over-represented proteins are related to reproductive functions. Our analysis identified 16 gene products encoding proteins involved in mineral supply, and allowed updating of the general model describing uterine ion transporters during eggshell calcification. A list of 57 proteins potentially secreted into the uterine fluid to be active in the mineralization process was also established. They were classified according to their potential functions (biomineralization, proteoglycans, molecular chaperone, antimicrobials and proteases/antiproteases).ConclusionsOur study provides detailed descriptions of genes and corresponding proteins over-expressed when the shell is mineralizing. Some of these proteins involved in the supply of minerals and influencing the shell fabric to protect the egg contents are potentially useful biological markers for the genetic improvement of eggshell quality.

The Effects of Melatonin on the Physical Properties of Bones and Egg Shells in the Laying Hen

Laying hens often experience unbalanced calcium utilization which can cause deficiencies in bone and egg mineralization. Because melatonin has been shown to affect bone mineralization in other animals, we examined whether treating hens with melatonin would affect eggshell thickness and improve skeletal performance, thereby reducing skeletal and egg shell defects. Birds were given a diet containing either low (30 µg/kg), medium (300 µg/kg), or high (3 mg/kg) concentrations of melatonin, or control feed through approximately one laying cycle. We examined the weight, length, and strength of egg, femur, tibia, and keel. Hens treated with a high concentration of melatonin showed significant strengthening in their femur and tibia, as measured by maximum force sustained and breaking force, compared to controls. Egg weights from hens treated with melatonin were significantly greater than those from hens that were not treated with melatonin. Conversely, egg shell mass of hens treated with melatonin was significantly lower than those of hens not treated with melatonin. Our data suggest that melatonin may affect the allocation of calcium to bone at the expense of egg shell mineralization.

The proteome of the calcified layer organic matrix of turkey (Meleagris gallopavo) eggshell

BackgroundChicken eggshell mineralization is a prominent model for biomineralization not only because of its importance for avian reproduction but also because of the commercial interest associated with eggshell quality. An analysis and comparison of the protein constituents of eggshells of several species would contribute to a better understanding of the shell mineralization process. The recent publication of the turkey genome sequence now provides a basis for the in-depth analysis of the turkey eggshell proteome.ResultsProteomic analysis of turkey acid-soluble and acid-insoluble organic eggshell matrix yielded 697 identified proteins/protein groups. However, intensity-based absolute quantification (iBAQ) results indicated that the 47 most abundant identified proteins already constituted 95% of the total turkey eggshell matrix proteome. Forty-four of these proteins were also identified in chicken eggshell matrix previously. Despite these similarities there were important and unexpected differences. While ovocleidin-116 and ovocalyxin-36 were major proteins constituting approximately 37% of the identified proteome, other members of the group of so-called eggshell-specific proteins were not identified. Thus ovocalyxin-21 and ovocalyxin-32 were missing among matrix proteins. Conversely, major turkey eggshell proteins were not detected in chicken, such as the bone protein periostin, the mammalian counterpart of which is involved in many aspects of bone metabolism and which represented 10-11% of the total identified proteome.ConclusionsEven members of the same avian family show important differences in eggshell matrix composition and more studies on the proteome and the transcriptome level will be necessary to identify a common toolkit of eggshell mineralization and to work out species differences among functional eggshell protein sets and their role in eggshell production.

Vulnerability of the Paper Nautilus (Argonauta nodosa) Shell to a Climate-Change Ocean: Potential for Extinction by Dissolution

Shell calcification in argonauts is unique. Only females of these cephalopods construct the paper nautilus shell, which is used as a brood chamber for developing embryos in the pelagic realm. As one of the thinnest (225 μm) known adult mollusc shells, and lacking an outer protective periostracum-like cover, this shell may be susceptible to dissolution as the ocean warms and decreases in pH. Vulnerability of the A. nodosa shell was investigated through immersion of shell fragments in multifactorial experiments of control (19 °C/pH 8.1; pCO(2) 419; Ω(Ca) = 4.23) and near-future conditions (24 °C/pH 7.8-7.6; pCO(2) 932-1525; Ω(Ca) = 2.72-1.55) for 14 days. More extreme pH treatments (pH 7.4-7.2; pCO(2) 2454-3882; Ω(Ca) = 1.20-0.67) were used to assess tipping points in shell dissolution. X-ray diffractometry revealed no change in mineralogy between untreated and treated shells. Reduced shell weight due to dissolution was evident in shells incubated at pH 7.8 (projected for 2070) after 14 days at control temperature, with increased dissolution in warmer and lower pH treatments. The greatest dissolution was recorded at 24 °C (projected for local waters by 2100) compared to control temperature across all low-pH treatments. Scanning electron microscopy revealed dissolution and etching of shell mineral in experimental treatments. In the absence of compensatory mineralization, the uncovered female brood chamber will be susceptible to dissolution as ocean pH decreases. Since the shell was a crucial adaptation for the evolution of the argonauts' holopelagic existence, persistence of A. nodosa may be compromised by shell dissolution in an ocean-change world.

Identification of Two Carbonic Anhydrases in the Mantle of the European Abalone Haliotis tuberculata (Gastropoda, Haliotidae): Phylogenetic Implications

Carbonic anhydrases (CAs) represent a diversified family of metalloenzymes that reversibly catalyze the hydration of carbon dioxide. They are involved in a wide range of functions, among which is the formation of CaCO(3) skeletons in metazoans. In the shell-forming mantle tissues of mollusks, the location of the CA catalytic activity is elusive and gives birth to contradicting views. In the present paper, using the European abalone Haliotis tuberculata, a key model gastropod in biomineralization studies, we identified and characterized two CAs (htCA1 and htCA2) that are specific of the shell-forming mantle tissue. We analyzed them in a phylogenetic context. Combining various approaches, including proteomics, activity tests, and in silico analyses, we showed that htCA1 is secreted but is not incorporated in the organic matrix of the abalone shell and that htCA2 is transmembrane. Together with previous studies dealing with molluskan CAs, our findings suggest two possible modes of action for shell mineralization: the first mode applies to, for example, the bivalves Unio pictorum and Pinctada fucata, and involves a true CA activity in their shell matrix; the second mode corresponds to, for example, the European abalone, and does not include CA activity in the shell matrix. Our work provides new insight on the diversity of the extracellular macromolecular tools used for shell biomineralization study in mollusks.

Identification of a novel metal binding protein, segon, in plasma of the eastern oyster, Crassostrea virginica

The second most abundant protein of eastern oyster plasma was purified, characterized and named segon. The 39 kDa protein as determined by SDS-PAGE under reducing conditions made up about 17% of plasma proteins and was found in extrapallial fluid. RACE reactions with primers designed from an EST sequence identified by BLAST search in GenBank using the N-terminal amino acid sequence obtained by Edman degradation of the purified protein, predicted a 997 bp complete cDNA that encoded 277 amino acids including a 16-residue signal peptide at the N-terminus. The deduced mature protein, composed of 261 amino acids, had a calculated molecular mass of 30,483.9 Da which was lower than the molecular mass of the purified protein measured by MALDI. The difference was likely due to post-translational modifications as the protein was predicted to have multiple sites for glycosylation and phosphorylation. The protein mRNA was detected in hemocytes by in situ hybridization and quantified in oyster tissues by RT-qPCR. Immunohistochemistry revealed that the protein was most abundant in tissues rich in blood sinuses like the gills and dorsally along the base of the mantle. ICP metal analysis of purified protein indicated highest association with zinc, calcium and iron and much greater metal content than in purified dominin, the most abundant protein of eastern oysters. Results of N-terminal and internal peptide sequencing of SDS-PAGE separated plasma proteins from Pacific, Suminoe and European flat oysters indicated that the second most abundant plasma protein is conserved. Several possible functions of segon in metal transport and detoxification, host defense, antioxidation and shell mineralization are proposed as they relate to its capacity to bind metals.

The shell matrix of the pulmonate land snail Helix aspersa maxima

In mollusks, the shell mineralization process is controlled by an array of proteins, glycoproteins and polysaccharides that collectively constitute the shell matrix. In spite of numerous researches, the shell protein content of a limited number of model species has been investigated. This paper presents biochemical data on the common edible land snail Helix aspersa maxima, a model organism for ecotoxicological purposes, which has however been poorly investigated from a biomineralization viewpoint. The shell matrix of this species was extracted and analyzed biochemically for functional in vitro inhibition assay, for amino acid and monosaccharides compositions. The matrix was further analyzed on 1 and 2D gels and short partial protein sequences were obtained from 2D gel spots. Serological comparisons were established with a set of heterologous antibodies, two of which were subsequently used for subsequent immunogold localization of matrix components. Our data suggest that the shell matrix of Helix aspersa maxima may differ widely from the shell secretory repertoire of the marine mollusks studied so far, such as the gastropod Haliotis or the pearl oyster Pinctada. In particular, most of the biochemical properties generally attributed to soluble shell matrices, such as calcium-binding capability, or the capacity to interfere in vitro with the precipitation of calcium carbonate or to inhibit the precipitation of calcium carbonate, were not recorded with this matrix. This drastic change in the biochemical properties of the landsnail shell matrix puts into question the existence of a unique molecular model for molluscan shell formation, and may be related to terrestrialisation.

Content and uptake of minerals in the yolk of broiler embryos during incubation and effect of nutrient enrichment

Although embryo and chicken growth and development rely on mineral nutrition, information on mineral levels in the egg compartments during incubation is limited. Accordingly, we examined P, Ca, Fe, Zn, Cu, and Mn levels in the yolk of breeder eggs during incubation and the effect of embryonic mineral (with specific nutrients) enrichment on yolk mineral levels and consumption. First, fertile eggs were examined on day of setting (DOS), embryonic day (E) 11, E13, E15, E17, E19, E20, and day of hatch (DOH) for the mineral content in the yolk (and albumen on DOS) by inductively coupled plasma atomic emission spectroscopy. Results showed that on DOS, the yolk is the major origin for Mn, P, Fe, Ca, Cu, and Zn. Interestingly, P, Fe, Zn, Cu, and Mn were mostly consumed from the yolk until E17, after which their consumption was very low. Consumption of P was constant until E17 and then decreased until E20. Consumption of Fe, Zn, Cu, and Mn was medium to mild until E11, increased between E11 and E17, and minimal between E17 and DOH. Enrichment treatment, where fertile eggs were divided into 2 groups [nonenriched (control) and enriched (with minerals, vitamins, and carbohydrates on E17 using the in ovo feeding method)] showed that the enriched group had higher Fe, Zn, Cu, and Mn levels than the nonenriched group and exhibited higher consumption of Fe, Zn, and Mn between E20 and DOH. Analysis of the shell mineral composition along incubation showed that the shell released low amounts of P, Fe, and Mn in comparison with the yolk mineral content. Therefore, we concluded that the shell is a minor source of these minerals. Studying the mineral resources and consumption of embryos can lead to a better understanding of the mineral limitations of embryos during incubation. Additionally, because minerals are important for the development of the embryo, the higher mineral levels and consumption observed in the enriched group may affect the development of critical organs, such as the skeletal system.

Novel Proteins from the Calcifying Shell Matrix of the Pacific Oyster Crassostrea gigas

The shell of the Pacific oyster Crassostrea gigas is composed of more than 99% CaCO₃ and of around 0.5% of occluded organic matrix. According to classical views, this matrix is supposed to regulate the shell mineral deposition. In this study, we developed one of the first proteomic approaches applied to mollusk shell in order to characterise the calcifying matrix proteins. The insoluble organic matrix, purified after demineralisation of the shell powder, was digested with trypsin enzyme, and separated on nano-LC, prior to nanospray quadrupole/time-of-flight analysis. MS/MS spectra were searched against the above 220,000 EST sequences available in the public database for Crassostrea. Using this approach, we were able to identify partial or full-length sequence transcripts that encode eight novel shell matrix proteins.

Characterization of the major plasma protein of the eastern oyster, Crassostrea virginica, and a proposed role in host defense

The major plasma protein of the eastern oyster, Crassostrea virginica, was purified, characterized and named dominin. SDS-PAGE analyses revealed that dominin consistently made up more than 40% of eastern oyster plasma and extrapallial fluid proteins. Three different forms of dominin were observed under non-reducing conditions. PCR and RACE primers designed from partial amino acid sequences obtained by tandem mass spectrometry of purified dominin identified 720bp of complete cDNA encoding 192 amino acid residues. Based on the deduced amino acid sequence of mature dominin, its molecular mass was calculated to be 19,389Da and was lower than the molecular mass of purified dominin measured by MALDI. This difference is likely due to post-translational modifications of dominin as the purified protein was found to be glycolysated, phosphorylated and likely sulfated. The amino acid sequence showed high similarity to the major plasma protein of the Pacific oyster (Crassostrea gigas), cavortin, and of the green-lipped mussel (Perna canaliculus), pernin, and to a recently described protein labeled as an extracellular superoxide dismutase from the Sydney rock oyster Saccostrea glomerata. While dominin was found to possess a Cu/Zn superoxide dismutase (SOD) domain, the domain was not completely conserved which explained why purified dominin lacked SOD activity. Dominin mRNA was detected in hemocytes by in situ hybridization and its expression measured by quantitative real time RT-PCR was significantly higher in winter than summer. Although the function(s) of dominin and homologous proteins is uncertain, the reported ability of cavortin to sequester iron and possibly limit the availability of this essential metal to pathogens suggests a potential role in host defense for this group of dominant plasma proteins. Other possible functions of dominin in antioxidation, wound repair, metal transport and shell mineralization are discussed leading us to conclude that dominin is likely a multifunctional protein.

Soft-Part Preservation in a Linguliform Brachiopod from the Lower Cambrian Wulongqing Formation (Guanshan Fauna) of Yunnan, South China

Linguliform brachiopods were important components of early Cambrian benthic communities. However, exceptionally preserved soft parts in Cambrian linguliform brachiopods are extremely sparse, and the most important findings are from the early Cambrian Chengjiang Konservat Lagerstatte of Kunming, southern China. Here we describe the first record of preserved soft-part anatomy in a linguli form brachiopod from the early Cambrian Guanshan fauna (Wu longging Formation, Palaeolenus Zone); a unit which is considerably younger than the Chengjiang fauna. The well preserved soft anatomy include linguliform pedicles, marginal setae and, in a few cases, an intact lophophore imprint. The pedicle has pronounced surface annulations, with its proximal-most part enclosing the apex of the ventral pseudointerarea; the pedicle is up to 51 mm long, corresponding to more than 4 times the sagittal length of the shell, and 12% of the maximum valve width. In details of their preservation, these new fossils exhibit striking similarities with the linguliforms from the older Chengjiang fauna, and all specimens are preserved in a compressed state as flattened impressions. The new linguliform has an elongate oval to subtriangular shell and an elongate triangular ventral pseudointerarea; the pedicle emerged from an apical foramen through a poorly preserved internal pedicle tube. The new linguliform is most similar to the mostly organic-shelled siphonotretoid-like brachiopod Acanthotretella spinosa, recently described from the classic middle Cambrian Burgess Shale Konservat Lagerstatte, British Columbia, Canada. The new species Acanthotretella decaius sp. nov. is described; it differs from A. spinosa in having a slightly thicker pedicle, and a larger and more rigid, probably partly mineralised shell, indicating that the mostly organic shell of A. spinosa may represent a secondary reduction of shell mineralisation. However, the spine-like setae of the new species are unfortunately poorly preserved only at the margin of the shell, but the new species is referred tentatively to the Superfamily Siphonotretoidea. The occurrence of A. decaius in the Guanshan fauna is the first lower Cambrian (Series 2, early Stage 4) record of both Acanthotretella and siphonotretoids, and it represents the first description of a lophophore and digestive tract from the siphonotretoid lineage.

Magnesium-aspartate-based crystallization switch inspired from shell molt of crustacean

Many animals such as crustacean periodically undergo cyclic molt of the exoskeleton. During this process, amorphous calcium mineral phases are biologically stabilized by magnesium and are reserved for the subsequent rapid formation of new shell tissue. However, it is a mystery how living organisms can regulate the transition of the precursor phases precisely. We reveal that the shell mineralization from the magnesium stabilized precursors is associated with the presence of Asp-rich proteins. It is suggested that a cooperative effect of magnesium and Asp-rich compound can result into a crystallization switch in biomineralization. Our in vitro experiments confirm that magnesium increases the lifetime of amorphous calcium carbonate and calcium phosphate in solution so that the crystallization can be temporarily switched off. Although Asp monomer alone inhibits the crystallization of pure amorphous calcium minerals, it actually reduces the stability of the magnesium-stabilized precursors to switch on the transformation from the amorphous to crystallized phases. These modification effects on crystallization kinetics can be understood by an Asp-enhanced magnesium desolvation model. The interesting magnesium-Asp-based switch is a biologically inspired lesson from nature, which can be developed into an advanced strategy to control material fabrications.

The Influence of Hydrostatic Pressure on Shell Mineralization ofAnodonta cygnea: A Comparative Study with a Hydrothermal Vent BivalveBathymodiolus azoricus

ABSTRACT The objective of this study was to determine at what level the shell mineralization of Anodonta cygnea, a shallow freshwater bivalve, is influenced by external physical—chemical factors, mainly concerning the habit and microstructure of the calcium carbonate crystals. A detailed examination of the inner shell layers of A. cygnea was carried out by scanning electron microscopy in animals living under natural environment conditions and after being exposed to artificially high hydrostatic pressure. Groups of 6 animals were exposed to different hydrostatic pressure (10, 20, 40, or 80 bar) in a hyperbaric chamber for 10 days. In general, we noted that the high pressure induced strong changes in the microstructure of all regions of the shell inner layer in A. cygnea, probably by altering organic matrix deposition, under every hyperbaric value. In fact, observations of the prismatic layer showed some significant alterations, presenting fibrous spherulitic crystalline arrangements instead of the nondenti...

Ultrastructure of avian eggshell during resorption following egg fertilization

For skeletal mineralization, the avian embryo mobilizes calcium from its calcitic eggshell. This occurs through dissolution of specific interior regions of the shell in a process that also weakens the shell to allow hatching. Here, we have examined eggshell ultrastructure during dissolution occurring between laying of a fertilized egg (with incubation) and hatching of the chick (Gallus gallus). We have focused on changes in shell mammillae where the majority of dissolution takes place. Using scanning electron microscopy, we describe differences in matrix-mineral structure and relationships not observed in unfertilized eggs (unresorbed eggshell). We document changes in the calcium reserve body - an essential sub-compartment of mammillae - consistent with it being an early, primary source of calcium essential for embryonic skeletal growth. Dissolution events occurring in the calcium reserve sac and in the base plate of the calcium reserve body, and similar changes in surrounding bulk mammillae structure, all correlate with advancing skeletal embryonic calcification. The changes in mammillae sub-structures can generally be characterized as mineral dissolutions revealing fine surface topographies on remaining mineral surfaces and the exposure of an extensive, intracrystalline (occluded) organic matrix network. We propose that this mineral-occluded network regulates how shell mineral is dissolved by providing dissolution channels facilitating calcium release for the embryonic skeleton.

Early Cambrian “Soft-Shelled” Brachiopods as Possible Stem-Group Phoronids

Brachiopods and phoronids are widely recognised as closely related lophophorate phyla. but the lack of morphological intermediates linking the bivalved bodyplan of brachiopods with tubular phoronids has frustrated precise phylogenetic placement. Here we describe Lingulosacculus nuda gen. et sp. nov., a new soft-shelled brachiopod from the Early Cambrian Mural Formation of western Alberta which provides a plausible candidate for a phoronid stem-group within (paraphyletic) Brachiopoda. In addition to its non-biomineralised shell, L. nuda had a ventral valve with an exceptionally long, pocket-like extension (pseudointerarea) that Would have allowed the transformation of criss-crossing brachiopod-type musculature to the longitudinal arrangement typical of phoronids. Soft-shelled linguliform brachiopods have previously been reported from both the Chengjiang and Burgess Shale Lagerstatten which, together with L. nuda. probably represent two independent losses of shell mineralisation in brachiopods.

Identification of Some Active Proteins in the Process of Hen Eggshell Formation

The hen eggshell is formed in a three-stage sequential process, namely, the initial stage (nucleation of calcite crystals), the active growth phase (linear deposition), and the terminal stage (inhibition of crystal formation). During these phases, different proteins are sequentially expressed in the uterine fluid. Some of them are thought to regulate the shell mineralization and particularly crystal growth. To identify proteins that are actively involved in this process, we have analyzed and compared the effects on CaCO3 precipitation in vitro of some commercial egg white proteins, some noncommercial purified fractions of the eggshell organic matrix and, also of uterine fluids extracted from the hen uterus during each one of the stages of calcification. Uterine fluids strongly increased the nucleation density with respect to commercial proteins and purified fractions of the shell. A few identified acidic proteins (ovocleidin-17, ovocalyxin-32, osteopontin and ovocleidin-116) showed a strong affinity for the CaCO3 surfaces and were selectively removed from the solution during its precipitation. These proteins may have an active role on CaCO3 growth, aggregation, and inhibition. Other proteins, with very different isoelectric points, seem to regulate the chemical environment in which the precipitation takes place, that is, by buffering the pH favoring crystal growth as the couple ovocleidin-17 and ovocalyxin-21.

Effects of Cd2+ on the calcium metabolism and shell mineralization of bivalve Anodonta cygnea

The survival of freshwater mussels is affected by cadmium ions because they accumulate in tissues and fluids and displace calcium ions in transport and regulation mechanisms. A preliminary study of the freshwater bivalve Anodonta cygnea under enriched Ca2+ (2 mM) water for different periods (3, 4, and 18 days), showed significant increase in calcium levels (p < 0.05) in the ventricular fluid with concentration proportional to time of exposure. Groups of A. cygnea were then exposed to different treatments for 4 days: Group 1 to Ca2+ (2 mM) enriched water as a control; Group 2 to a sub-lethal concentration (10−6 M) of Cd2+; Group 3 to an injection of vitamin D (1340 IU mL−1); Group 4 to an injection of SEA0400 (950 µg mL−1), a sodium/calcium exchanger (NCX) inhibitor. Fluid samples from different compartments of the animals were analyzed for Ca2+ and Cd2+ composition as well as for other ions relevant to the osmoregulation (Na+, Mg2+, K+, and Cl−) and their osmolarity. The treatment groups had significantly higher calcium concentrations in their ventricular fluid (p < 0.05) under Cd2+ and vitamin D, also in pericardium fluid under Cd2+, vitamin D, and SEA0400. We infer a specific transport mechanism from the intestinal to the ventricular fluid that may be induced by vitamin D. A general internal acidosis by Cd2+, releasing calcium from the calcareous concretions and a specific inhibition of calcium resorption, by the SEA0400, from the pericardium towards the ventricle is discussed. Cd2+ incubation significantly augmented (p < 0.05) the cadmium contents of all experimental fluids and tissues. Scanning electron microscope (SEM) imaging of the border regions of the shell showed clear ultrastructural changes in respone to Cd2+ incubation, suggesting a direct influence of this ion on the shell biomineralization mechanisms.

Shell repair process in the green ormer Haliotis tuberculata: A histological and microstructural study

In the present paper, juvenile and adult shells of the green ormer Haliotis tuberculata (‘Oreille de Saint-Pierre’) were perforated in a zone close to the shell edge and the shell repair process was followed at two levels: (1) by observing the histology of the calcifying mantle in the repair zone and (2) by analyzing with SEM the microstructure of the shell repair zone. Histological data clearly show the presence of calcium carbonate granules into the connective tissues, but not in the epithelial cells. This suggests that calcium carbonate granules are synthesized by sub-epithelial cells and actively transported through the epithelium to the repair zone, via a process which may be similar to that described by Mount et al. [Mount, A.S., Wheeler, A.P., Paradkar, R.P., Snider, D., 2004. Hemocyte-mediated shell mineralization in the eastern oyster. Science 304, 297–300]. Furthermore, SEM observations show that the repair zone exhibits different stratified microstructures (spherulitic, thin prismatic, blocklike, sub-nacreous, nacreous, foliated-like), some of which are not continuous ( i. e. lenticular) along the repair zone. This suggests a complex secreting regime of the calcifying mantle and an elaborate geometry of the epithelium involved in shell repair.

Effects of increased seawater pCO2 on early development of the oyster Crassostrea gigas

AB Aquatic Biology Contact the journal Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections AB 1:91-98 (2007) - DOI: https://doi.org/10.3354/ab00009 Effects of increased seawater pCO2 on early development of the oyster Crassostrea gigas Haruko Kurihara*, Shoji Kato, Atsushi Ishimatsu Institute for East China Sea Research, Nagasaki University, 1551-7 Tairamachi, Nagasaki, 851-2213, Japan *Email: harukoku@e-mail.jp ABSTRACT: This study demonstrated that the increased partial pressure of CO2 (pCO2) in seawater and the attendant acidification that are projected to occur by the year 2300 will severely impact the early development of the oyster Crassostrea gigas. Eggs of the oyster were artificially fertilized and incubated for 48 h in seawater acidified to pH 7.4 by equilibrating it with CO2-enriched air (CO2 group), and the larval morphology and degree of shell mineralization were compared with the control treatment (air-equilibrated seawater). Only 5% of the CO2 group developed into normal ‘D-shaped’ veliger larvae as compared with 68% in the control group, although no difference was observed between the groups up to the trochophore stage. Thus, during embryogenesis, the calcification process appears to be particularly affected by low pH and/or the low CaCO3 saturation state of high-CO2 seawater. Veliger larvae with fully mineralized shells accounted for 30% of the CO2-group larvae, compared with 72% in the control (p < 0.005). Shell mineralization was completely inhibited in 45% of the CO2-group larvae, but only in 16% of the control (p < 0.05). Normal D-shaped veligers of the control group exhibited increased shell length and height between 24 and 48 h after fertilization, while the few D-shaped veligers of the CO2 group showed no shell growth during the same period. Our results suggest that future ocean acidification will have deleterious impacts on the early development of marine benthic calcifying organisms. KEY WORDS: Carbon dioxide · pH · Crassostrea gigas · Calcification · Larval development · Marine bivalves · Calcium saturation · Ocean acidification Full text in pdf format PreviousCite this article as: Kurihara H, Kato S, Ishimatsu A (2007) Effects of increased seawater pCO2 on early development of the oyster Crassostrea gigas. Aquat Biol 1:91-98. https://doi.org/10.3354/ab00009 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AB Vol. 1, No. 1. Online publication date: October 09, 2007 Print ISSN: 1864-7782; Online ISSN: 1864-7790 Copyright © 2007 Inter-Research.

A Novel Extrapallial Fluid Protein Controls the Morphology of Nacre Lamellae in the Pearl Oyster, Pinctada fucata

Mollusk shell nacre is known for its superior mechanical properties and precisely controlled biomineralization process. However, the question of how mollusks control the morphology of nacre lamellae remains unresolved. Here, a novel 38-kDa extrapallial fluid (EPF) protein, named amorphous calcium carbonate-binding protein (ACCBP), may partially answer this question. Although sequence analysis indicated ACCBP is a member of the acetylcholine-binding protein family, it is actively involved in the shell mineralization process. In vitro, ACCBP can inhibit the growth of calcite and induce the formation of amorphous calcium carbonate. When ACCBP functions were restrained in vivo, the nacre lamellae grew in a screw-dislocation pattern, and low crystallinity CaCO(3) precipitated from the EPF. Crystal binding experiments further revealed that ACCBP could recognize different CaCO(3) crystal phases and crystal faces. With this capacity, ACCBP could modify the morphology of nacre lamellae by inhibiting the growth of undesired aragonite crystal faces and meanwhile maintain the stability of CaCO(3)-supersaturated body fluid by ceasing the nucleation and growth of calcite. Furthermore, the crystal growth inhibition capacity of ACCBP was proved to be directly related to its acetylcholine-binding site. Our results suggest that a "safeguard mechanism" of undesired crystal growth is necessary for shell microstructure formation.