Antho-RFamide effect on light production in the bioluminescent sea pen Pennatula phosphorea (Octocorallia, Pennatulacea)

Bioluminescence in anthozoans is a rapid and coordinated response that relies on nervous control, yet the neurochemical mechanisms underlying light production remain poorly understood. In the sea pen Pennatula phosphorea, mechanical stimulation elicits propagating waves of green light often coupled with muscular contraction, suggesting tight integration between neural, muscular and luminous systems. Here, we investigated the presence and role of RFamide neuropeptides in the control of bioluminescence in P. phosphorea by combining transcriptomic analysis and pharmacological experiments. We identified Antho-RFamide-like precursor sequences in the P. phosphorea transcriptome, characterized by repeated conserved RFamide motifs typical of anthozoan neuropeptide precursors. Phylogenetic analysis revealed a clear differentiation between octocorallian and hexacorallian Antho-RFamide precursor sequences, while highlighting substantial variation in motif repetition number across anthozoan species. Pharmacological assays demonstrated that Antho-RFamide can trigger light emission, providing direct evidence for its involvement in luminescence control. These results support a model in which Antho-RFamide acts as an ancestral neuropeptidergic component of the bioluminescence response, operating alongside catecholaminergic pathways to regulate light emission. We further propose that variation in Antho-RFamide precursor architecture may influence neuropeptide signaling capacity and contribute to functional diversification of the neuropeptide role, including luminescence control within luminous anthozoans. By providing the first functional evidence linking neuropeptide signaling to light production in a sea pen species, this study identified a previously unrecognized role of RFamide peptides in the control of bioluminescence and revealed a complex, multi-layered neurochemical regulatory system underlying light emission in anthozoans.