Pigmented region transcriptomics identifies molecular pathways potentially associated with microbial transport in the...

In certain cephalopods, the female-specific accessory nidamental gland (ANG) harbors dense microbial communities that are transported to the nidamental gland, incorporated into glandular secretions, and delivered to egg capsules to protect embryos. In mature females, the ANG shows pigmented regions with distinct microbiomes, though host responses remain unclear. Transcriptomic analyses of these pigmented regions in the ANG of mature female bigfin reef squid (Sepioteuthis lessoniana) revealed reduced protein synthesis and enhanced fluid/ionic homeostasis, along with enrichment of muscle contraction-related processes, suggesting potential mechanisms associated with microbial transport. Weighted gene co-expression network analysis (WGCNA) identified blue and royalblue modules linked to individual variation and pigment color; the blue module was enriched in cell cycle and protein synthesis-associated processes, while the royalblue module was involved in energy metabolism, fluid/ionic homeostasis, and host-microbiome interaction-associated processes. These results suggest that pigment-associated ANG microenvironments regulate local metabolism, with the host maintaining homeostasis and potentially supporting processes associated with microbial transfer toward the nidamental gland.