Influence of thermal variability on biomineralization-related traits in the tropical scallop Nodipecten subnodosus

Marine bivalves rely on physiological and structural mechanisms to cope with environmental variability, yet shell formation responses to thermal fluctuations remain poorly understood. This study evaluated shell development and biomineralization-related responses in juvenile lion’s paw scallops, Nodipecten subnodosus, derived from Laguna Ojo de Liebre (LOL) and Bahía de Los Ángeles (BA). Juveniles were exposed for 15 days to constant temperature, regular thermal oscillations, or chaotic thermal oscillations. Shell responses were assessed using shell index (SI), expression of a putative mucin-related transcript, and qualitative scanning electron microscopy. Tank-level analysis detected a significant overall effect of source population on SI, whereas neither thermal regime nor its interaction with source population was statistically significant. A model-estimated contrast showed that BA scallops had a higher SI than LOL scallops under the chaotic regime; however, this difference does not demonstrate that chaotic oscillations directly reduced shell deposition. Expression of the putative mucin-related transcript did not differ significantly in the comparisons evaluated. Apparent alterations in outer and inner shell structures morphologically consistent with calcitic and aragonitic organisation were observed under both oscillatory regimes. Overall, SI, transcript expression, and shell microstructure showed non-parallel responses, indicating that these endpoints capture complementary aspects of shell formation under thermal variability.