Microstructure Organization and Composition of Argopecten purpuratus Scallop Shell

The scallop Argopecten purpuratus is distributed alongside the coast of Peru and Chile, representing a key species in the aquaculture industry, with significant socioeconomic importance due to its high level of worldwide exports. While several studies have addressed how this species responds to environmental changes aiming to increase industry relevant traits like growth, its shell microstructure has not yet been well described. This aspect is key for understanding how potential environmental changes, such as ocean acidification, may affect the species. In this study, we show that A. purpuratus shell has a three-layered structure. The outer layer is made of granular calcite crystals, followed by a second layer underneath composed of small platy crystals arranged in packs with coherent crystallographic orientation, which gives the impression of large grains under EBSD. The third and thickest layer consists of foliated calcite arranged in sheets with alternating directions. This general scheme is altered towards the dorsal shell side, with the presence of the prismatic aragonitic myostracum intersecting those layers, and the addition of a complex cross-foliated layer underneath. Overall, this study provides key data on the shell microstructure of A. purpuratus , forming a foundation for future studies focused on this vital structure for the organism´s survival, particularly in the context of ongoing current climate change.