Photoperiod mediated transcriptomic regulation of spawning in Octopus mimus

Background: The reproductive cycle of Octopus mimus is regulated by environmental and hormonal factors, with photoperiod playing a key role in spawning induction and reproductive maturation. Understanding its underlying molecular mechanisms is essential for developing strategies to enhance controlled reproduction in aquaculture. Methods: We analyzed the expression of genes involved in the photoperiod-activated spawning induction cascade in the optic lobe and its downstream effects on the oviducal gland by performing transcriptomic analyses on females exposed to continuous light (24-0), which inhibits reproductive development, and a natural photoperiod, which induces spawning. mRNA sequencing (RNA-Seq), quality control, gene annotation, and differential expression analyses were conducted using edgeR. Results: Spawning was completely inhibited under constant light, while 80% of control females spawned. Expression profiling revealed 89 downregulated and 34 upregulated genes in the optic lobe, and 178 downregulated and 237 upregulated genes in the oviducal gland, including key orthologs such as FMRFamide and myomodulin. Conclusions: These results show that the optic lobe integrates photoperiodic cues that modulate reproductive activation via a neuroendocrine cascade and coordinates spawning regulation through the oviducal gland, providing insights for improving reproductive control in aquaculture systems.