| 1. |
- Clark, M. S., et al.
(författare)
-
Deciphering mollusc shell production: the roles of genetic mechanisms through to ecology, aquaculture and biomimetics
- 2020
-
Ingår i: Biological Reviews. - : Wiley. - 1464-7931 .- 1469-185X. ; 95:6, s. 1812-37
-
Tidskriftsartikel (refereegranskat)abstract
- Most molluscs possess shells, constructed from a vast array of microstructures and architectures. The fully formed shell is composed of calcite or aragonite. These CaCO(3)crystals form complex biocomposites with proteins, which although typically less than 5% of total shell mass, play significant roles in determining shell microstructure. Despite much research effort, large knowledge gaps remain in how molluscs construct and maintain their shells, and how they produce such a great diversity of forms. Here we synthesize results on how shell shape, microstructure, composition and organic content vary among, and within, species in response to numerous biotic and abiotic factors. At the local level, temperature, food supply and predation cues significantly affect shell morphology, whilst salinity has a much stronger influence across latitudes. Moreover, we emphasize how advances in genomic technologies [e.g. restriction site-associated DNA sequencing (RAD-Seq) and epigenetics] allow detailed examinations of whether morphological changes result from phenotypic plasticity or genetic adaptation, or a combination of these. RAD-Seq has already identified single nucleotide polymorphisms associated with temperature and aquaculture practices, whilst epigenetic processes have been shown significantly to modify shell construction to local conditions in, for example, Antarctica and New Zealand. We also synthesize results on the costs of shell construction and explore how these affect energetic trade-offs in animal metabolism. The cellular costs are still debated, with CaCO(3)precipitation estimates ranging from 1-2 J/mg to 17-55 J/mg depending on experimental and environmental conditions. However, organic components are more expensive (similar to 29 J/mg) and recent data indicate transmembrane calcium ion transporters can involve considerable costs. This review emphasizes the role that molecular analyses have played in demonstrating multiple evolutionary origins of biomineralization genes. Although these are characterized by lineage-specific proteins and unique combinations of co-opted genes, a small set of protein domains have been identified as a conserved biomineralization tool box. We further highlight the use of sequence data sets in providing candidate genes forin situlocalization and protein function studies. The former has elucidated gene expression modularity in mantle tissue, improving understanding of the diversity of shell morphology synthesis. RNA interference (RNAi) and clustered regularly interspersed short palindromic repeats - CRISPR-associated protein 9 (CRISPR-Cas9) experiments have provided proof of concept for use in the functional investigation of mollusc gene sequences, showing for example that Pif (aragonite-binding) protein plays a significant role in structured nacre crystal growth and that theLsdia1gene sets shell chirality inLymnaea stagnalis. Much research has focused on the impacts of ocean acidification on molluscs. Initial studies were predominantly pessimistic for future molluscan biodiversity. However, more sophisticated experiments incorporating selective breeding and multiple generations are identifying subtle effects and that variability within mollusc genomes has potential for adaption to future conditions. Furthermore, we highlight recent historical studies based on museum collections that demonstrate a greater resilience of molluscs to climate change compared with experimental data. The future of mollusc research lies not solely with ecological investigations into biodiversity, and this review synthesizes knowledge across disciplines to understand biomineralization. It spans research ranging from evolution and development, through predictions of biodiversity prospects and future-proofing of aquaculture to identifying new biomimetic opportunities and societal benefits from recycling shell products.
|
|
| 2. |
- Sillanpää, Kirsikka, et al.
(författare)
-
Calcium transfer across the outer mantle epithelium in the Pacific oyster, Crassostrea gigas
- 2018
-
Ingår i: Proceedings of the Royal Society B: Biological Sciences. - : The Royal Society. - 0962-8452 .- 1471-2954. ; 285:1891
-
Tidskriftsartikel (refereegranskat)abstract
- Calcium transport is essential for bivalves to be able to build and maintain their shells. Ionized calcium (Ca2þ) is taken up from the environment and eventually transported through the outer mantle epithelium (OME) to the shell growth area. However, the mechanisms behind this process are poorly understood. The objective of the present study was to characterize the Ca2þ transfer performed by the OME of the Pacific oyster, Crassostrea gigas, as well as to develop an Ussing chamber technique for the functional assessment of transport activities in epithelia of marine bivalves. Kinetic studies revealed that the Ca2þ transfer across the OME consists of one saturable and one linear component, of which the saturable component fits best to Michaelis – Menten kinetics and is characterized by a Km of 6.2 mM and a Vmax of 3.3 nM min21. The transcellular transfer of Ca2þ accounts for approximately 60% of the total Ca2þ transfer across the OME of C. gigas at environmental Ca2þ concentrations. The use of the pharmacological inhibitors: verapamil, ouabain and caloxin 1a1 revealed that voltage-gated Ca2þ-channels, plasma-membrane Ca2þ-ATPase and Naþ/Ca2þ-exchanger all participate in the transcellular Ca2þ transfer across the OME and a model for this Ca2þ transfer is presented and discussed. © 2018 The Author(s) Published by the Royal Society. All rights reserved.
|
|
| 3. |
- Sillanpää, Kirsikka
(författare)
-
Calcium transport in the Pacific oyster, Crassostrea gigas - in a changing environment
- 2019
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Pacific oyster, Crassostrea gigas, is globally one of the most important farmed bivalve species. A prominent features of the C. gigas is the thick CaCO3 shell covering the body of the animal and protecting it from the environment. To be able to produce the shell, the oysters need to take up calcium from the environment and transport it to the shell forming area. The mantle tissue, separating the rest of the body from the shell, is suggested to be of central importance for both uptake of calcium and its transfer to the shell. The final part in this route is the transfer of the ion across the outer mantle epithelium (OME). The Ca has been suggested to be transferred across the OME in one or more of the following forms: as ionic calcium (Ca2+), as calcium bound to proteins or inorganic ligands, as CaCO3 inside vesicles or cells in the hemolymph. The uptake of Ca and other ions for the shell formation, as well as the conditions affecting the calcification process, are dependent on external conditions such as salinity, temperature and pH. As climate change has predicted to change these conditions in the future, also the shell formation of oysters might be affected. In this thesis, the uptake and transport of calcium from the environment to the shell forming area in C. gigas were investigated. Calcium uptake and transport in the hemolymph were analysed by exposing the oysters to water containing radioactive calcium after shell regeneration had been induced through an artificial cut, to accelerate shell formation. The uptake and transport of calcium in the different hemolymph fractions and mantle tissue were then followed. The transfer of calcium ions across the OME was investigated in vitro using live OME mounted in specialized Ussing chambers. The kinetics of the Ca2+ transport was assessed as were the effects of pharmacological tools inhibiting selected potential Ca2+ transporters and channels. Additionally, the mantle genome was searched for these potential ion transporters and channels. The expression of the proteins as well as their cellular localisation in the OME, was confirmed by immunohistochemistry and western blot. Finally, effects of a dilute environmental salinity on the OME ion transfer as well as on the mRNA expression of potential Ca2+ transporters and channels were examined In C. gigas calcium was taken up from the environment and transported in the hemolymph mostly as Ca2+. The transfer of Ca2+ across the OME consisted of a passive, paracellular component and a transcellular, active transport component. A combination of physiological and functional studies, transcriptome analysis and protein expression analyses through immunological methods made it possible to postulate a model for Ca transfer across the OME of C. gigas. The Ca was transferred following two pathway: 1) 60% was transcellularly transported and entered the OME cells through basally located voltage-gated Ca channels (VGCCs) and was then excreted across the apical membrane by Ca2+-ATPases (PMCA) and Na+/Ca2+-exchangers (NCX), the latter using the Na+ gradient created by a basal NKAs to function. 2) the remaining 40% was diffusing across the OME through the paracellular pathway. Ionic Ca2+ transfer, total active ion transport and paracellular permeability all decreased when C. gigas were exposed to diluted seawater (50%). The pattern of changes in mRNA expression of Ca transporters and channels in the OME cells suggest that the cells are trying to compensate for the decreased Ca levels in the diluted seawater. Expression of intracellular Ca-ATPases (SERCAs), transporting Ca2+ into intracellular stores decreases, while membrane bound Ca2+ channels and NCX mRNA expression increases. These changes suggest that the cells strive to maintain a high enough intracellular Ca2+ concentration to achieve a sufficient Ca2+ flow across the OME for shell growth. However, as the Ca2+ transfer across the OME decreased when exposed to 50 % seawater, these compensatory mechanisms were not sufficient. Overall, these results indicate that the oyster C. gigas may face problems with shell calcification in areas where the salinity of the seawater have been predicted to decreaseas a result of current climate changes.
|
|
| 4. |
- Sillanpää, Kirsikka, et al.
(författare)
-
Dilution of Seawater Affects the Ca2+ Transport in the Outer Mantle Epithelium of Crassostrea gigas
- 2020
-
Ingår i: Frontiers in Physiology. - : Frontiers Media SA. - 1664-042X. ; 11:1
-
Tidskriftsartikel (refereegranskat)abstract
- Varying salinities of coastal waters are likely to affect the physiology and ion transport capabilities of calcifying marine organisms such as bivalves. To investigate the physiological effect of decreased environmental salinity in bivalves, adult oysters (Crassostrea gigas) were exposed for 14 days to 50% seawater (14) and the effects on mantle ion transport, electrophysiology and the expression of Ca2+ transporters and channels relative to animals maintained in full strength sea water (28) was evaluated. Exposure of oysters to a salinity of 14 decreased the active mantle transepithelial ion transport and specifically affected Ca2+ transfer. Gene expression of the Na+/K+-ATPase and the sarco(endo)plasmic reticulum Ca2+-ATPase was decreased whereas the expression of the T-type voltage-gated Ca channel and the Na+/Ca2+-exchanger increased compared to animals maintained in full SW. The results indicate that decreased environmental salinities will most likely affect not only osmoregulation but also bivalve biomineralization and shell formation.
|
|
