The Ca2+ channel and calmodulin regulate the settlement and metamorphosis of the mussel Mytilus galloprovincialis induced by CaCl2, epinephrine and bioflim

The settlement and metamorphosis (SM) of marine bivalves represents a critical developmental transition from the planktonic larval stage to the sedentary adult stage. In this study, we evaluated the inductive efficiency of calcium ions (Ca²⁺), epinephrine (EPI), and bacterial biofilms on larval SM of Mytilus galloprovincialis, as well as the inhibitory efficiency of Ca²⁺ channel blockers (Zn²⁺, Ni²⁺, verapamil) and the calmodulin (CaM) inhibitor N-(6-aminohexyl)-5-chloro-1-naphthalene sulfonamide (W-7). Our results showed that the optimal concentrations of Ca²⁺ and EPI for promoting M. galloprovincialis SM were 50 mM and 10 μM, respectively, and both inducers exhibited bell-shaped concentration response curves. A 20-day-old biofilm also effectively induced SM in M. galloprovincialis. Furthermore, ZnCl2, NiCl2, verapamil, and W-7 significantly reduced SM rates induced by Ca2+, EPI, or biofilm. As inhibitor concentrations increased, SM rates dropped sharply; at specific concentrations (e.g., 10μM VER, 100 μM ZnCl2), SM was nearly eliminated. Collectively, these findings reveal that M. galloprovincialis SM is a tightly coordinated physiological process, mediated by the integration of external inductive cues and intracellular Ca²⁺-dependent signaling cascades involving transient receptor potential melastatin 7 (TRPM7) channels, L-type voltage-gated Ca²⁺ channels (VGCCs), and calmodulin (CaM). This research provides insights to optimize aquaculture yields (via targeted SM promotion), supports the development of eco-friendly biofouling management strategies (via SM inhibition), and offers a theoretical basis for bivalve population restoration in ecological conservation. Despite these contributions, future studies should address key knowledge gaps: (1) applying comparative transcriptomics or proteomics to directly identify SM-related genes and proteins, to clarify the molecular underpinnings of the observed regulatory effects; and (2) conducting mesocosm-scale and long-term field experiments to validate the practical utility of these inducers and inhibitors under natural or aquaculture-relevant conditions.