Calcium transport in the Pacific oyster, Crassostrea gigas - in a changing environment

• Main Author: Sillanpää, Kirsikka
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: 2019
• Subjects: Climate changes; Ussing chambers; Calcium uptake; Sodium/potassium ATPase; Calcium ATPase; Sodium/calcium exchanger; Calcium channel; Hemocytes; Mantle epithelium; Crassostrea gigas; Pacific oyster
• Online Access: http://hdl.handle.net/2077/61703

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 ...