Functional capacities of gill mitochondria in oysterCrassostrea gigasduring an emersion/immersion tidal cycle

Abstract

-Sessile animals that live on the foreshore undergo tidal cycles, and have to face variations in physical and chemical parameters such as oxygen concentration. During emersion, availability of dissolved oxygen can be lowered for bivalves, which have only a small reserve of seawater inside their closed shell. Differences in oxygen concentration are thus expected to lead to modifications of the metabolism, including changes in mitochondrial activity. Previous studies investigated air exposure under extreme conditions, which do not always reflect environmental conditions these invertebrates have to cope with. In this study, oxidative capacities of gill mitochondria of the oyster Crassostrea gigas were studied during a tidal cycle period, by comparing oysters collected after emersion and immersion. Only minor differences were found in state 3 (oxidative phosphorylation) or state 4 (non-phosphorylating oxygen consumption) rates between the two conditions. Similarly, no difference was observed in cytochrome c oxidase activity or in oxygen consumption related to maximal electron flux through complexes I-IV, II-IV and IV. While capacities of substrate oxidation were maintained in both emersion and immersion conditions, capacity of mitochondria to produce adenosine triphosphate (ATP) was significantly lower in oysters sampled during emersion. These results suggest that although C. gigas could maintain aerobic metabolism during emersion period within a tidal cycle in its environment, energy producing mechanisms are affected.

Laboratory conditioning modifies properties of gills mitochondria from the Pacific oyster Crassostrea gigas

“…Procedures for mitochondrial isolation are detailed in Dudognon et al (2013). Oxygen consumption was measured immediately on the fresh mitochondrial preparations.…”

“…Cytochrome c oxidase was measured in mitochondrial preparations, and citrate synthase (CS) activity was measured in gill extracts according to Dudognon et al (2013Dudognon et al ( , 2014, respectively.…”

“…For marine bivalves, changes in abiotic conditions, such as temperature, oxygenation, salinity and desiccation, lead to regulated physiological adjustments that can affect growth and reproduction. At the cellular level, changes in mitochondrial function and membrane composition in response to abiotic factors have been demonstrated in bivalves (Glémet and Ballantyne 1995;Gillis and Ballantyne 1999;Guderley 2004;Sussarellu et al 2013;Dudognon et al 2013). This ability to adjust mitochondrial structure and function is thought to be critical in controlling energy production under changing environmental conditions (Guderley 2004;Bremer and Moyes 2011).…”

Assessment of Metabolism of the Eastern Oyster and Eastern Elliptio Using NMR Spectroscopy

“…The study of the metabolic profile of those marine organisms could be particularly useful for understanding changes in physiology, pharmacology and toxicology. 4 Organ specific metabolic fingerprints can establish time dependent assessments necessary for interpreting functional adaptations to environmental and nutritional challenges. Traditionally radioactive tracers have been used for such studies.…”

“…4,11 Oysters also constitute an useful model because (i) the oysters have well separated organs with certain functions resulting in distinct metabolic profiles, (ii) its organs are lipid-rich making them easily distinguishable with T2-weighted MRI, (iii) oysters are sessile creatures and easy to immobilize during data accumulation allowing long acquisition times for high resolution MRI images without image blurring effects. 8 Its relatively few organs are easily delineated in the MR image and there is sufficient understanding of their functions based on classical assays to support interpretation of NMR results.…”