The Xiamen Symposium on Marine Environmental Sciences (XMAS 2025)

The bivalve planktonic development is a critical phase during which larvae must secrete the first calcium carbonate shell, the prodissoconch I (PD I). As the PD I formation is in close contact with seawater, this process can be negatively affected by adverse seawater carbonate chemistry, such as elicited by ocean acidification. Larval shell formation is a bottleneck in bivalve development that has been associated with increased mortality due to environmental stress. It is hypothesized that bivalve larvae can regulate shell formation and environmental change influence through biologically controlled biomineralization that involves a complex extracellular shell proteome. However, the plasticity of larval shell proteome as an adaptive response during PD I formation is unknown. We assessed the PD I shell proteome of Magallana hongkongensis (Lam & B. Morton, 2003, Hong Kong oyster) under adverse carbonate chemistry (pH 7.4) to understand the regulatory capacity of larval shell formation. Our results revealed that larvae can upregulate several calcium-binding proteins, downregulate proton-generating processes, and putative calcification inhibitors. Inter-specific comparisons show that the larval shell proteome fraction of M. hongkongensis is lower but more diverse than the mussel Mytilus edulis which displays higher sensitivity to similar conditions. However, the oyster larval shell protein redundancy decreases in adverse carbonate chemistry, indicating a potential trade-off. Our data also suggest that direct cellular control and biologically induced mechanisms may be involved in PD I formation. This study provides the first glimpse into bivalve larval shell plasticity at the shell proteomic level and highlights favorable traits that can inform aquaculture and conservation decision-making.

Bivalve larval shell, Oyster, Shell protein, Biomineralization, Development and Evolution, Ocean acidification