Integrated morphological and transcriptomic analysis of sucker development in Octopus minor.

Coleoid cephalopods are excellent models for evolutionary and developmental studies due to their centralized nervous system, short life span, and sophisticated sense organs. Arm suckers, essential for predation, manipulation, and locomotion, have been studied in Decapodiformes, but little is known at the cellular and molecular levels. Here, we investigated sucker development in Octopus minor from the embryo to the juvenile stage using morphological, histological, immunostaining, scanning electron microscopy (SEM), in situ hybridization, and transcriptomic analyses. SEM revealed that suckers initially form symmetrically and later become asymmetrical through an embedding process. Histology showed progressive structural differentiation, while immunostaining with acetylated α-tubulin and phalloidin visualized nerve fiber and muscle development. Transcriptome profiling of embryonic stages 12, 14, and 20 identified 2,349 differentially expressed genes (DEGs) linked to arm and muscle development. Among them, Omi-Gata4, Omi-Mef2A, and WNT signaling molecules (Omi-Fzd9, Omi-Wnt2, Omi-Wnt5) exhibited increased expression in arms and developing suckers, consistent with in situ hybridization results. These findings suggest that WNT signaling contributes to sucker muscle development in O. minor, paralleling its conserved role in vertebrates. This study provides new insights into the embryonic morphogenesis of arms and suckers, highlighting the molecular and cellular mechanisms that shape cephalopod appendages.