Physiological mechanisms of shell microstructural regulation in Japanese pearl oyster under hypoxic stress: Insights into molluscan resilience against environmental changes

Investigating the anomalous expression of nacre, one of the most common microstructures of mollusks, as an environmental archive and its genomic background provides novel insights into biomineralization. In this study, we aimed to elucidate the physiological responses of the Japanese pearl oyster, Pinctada fucata, under hypoxia, focusing on shell microstructure plasticity. We conducted RNA-seq analysis in specimens from different depths with different oxygen concentrations and observed changes in shell microstructures. We found differences in shell microstructure and distinct gene expression profiles under hypoxia and normoxia. Several shell matrix protein genes were downregulated under hypoxia, suggesting their role in shell formation. We estimated the dissolved oxygen threshold affecting the physiological resistance of P. fucata to microstructural alterations. These results indicate that molluscan shell microstructures are under genetic control in response to environmental stressors. Our findings regarding the anomalous expression of nacre provide insights into the response of biomineralization in mollusks to hypoxia, and contribute to the sustainable use of pearl aquaculture resources.