Exogenous adenosine promotes barnacle (Amphibalanus amphitrite) cyprid settlement through molecular signaling and improved adhesive mechanics.

Marine biofouling caused by barnacle gregarious settlement poses significant challenges to various industries and ecosystems, such as increased drag on ship hulls, elevated fuel consumption, and heightened maintenance costs. While natural chemical cues are instrumental in driving barnacle settlement, the underlying mechanisms remain incompletely understood. In this work, we investigated the effects of adenosine (Ado), a settlement pheromone of Amphibalanus amphitrite cyprids, on cyprid exploration behavior, nano-mechanical properties of footprints, and gene expression using atomic force microscopy (AFM) and omics analysis. Results indicate that Ado significantly increases the settlement rate and exploration frequency of cyprids, and enhances the expression of the settlement-inducing protein complex (SIPC, which attracts other cyprids to settle in a gregarious manner). AFM results reveal that Ado-treated cyprids exhibit enhanced adhesion, self-healing, elasticity, and mechanical strength in their footprints, which may help them resist the shear forces from seawater. Transcriptome analysis suggests that Ado triggers the up-regulation of the transcription factors FTZ-F1 and Hr39, which may activate the 20E hormonal signaling pathway and promote the settlement process. Furthermore, Ado up-regulates the cement protein genes of CP19K-like4 and CP100K, which are involved in the initial adhesion process. These findings provide valuable insights into the role of pheromones in promoting barnacle settlement and offer a deeper understanding of the mechanisms driving this behavior.