Genome-wide identification and transcriptomic analysis of putative olfactory genes in Pomacea canaliculata.

Chemosensation plays a pivotal role in foraging, mate recognition, and environmental adaptation for the invasive apple snail Pomacea canaliculata. However, the molecular foundations and ontogenetic dynamics of its olfactory system remain insufficiently characterized. In this study, we identified putative olfactory genes from whole-genome data and profiled their expression in nine different tissues, and also in cephalic tentacle tissues at four developmental stages. A total of 178 candidate olfactory-related genes were identified, including 90 olfactory receptors (ORs), 32 ionotropic receptors/ionotropic glutamate receptors (IRs/iGluRs), 16 lipocalins, 20 Niemann-Pick type C2 proteins (NPC2s), 4 sensory neuron membrane proteins (SNMPs), and 16 degenerin/epithelial sodium channels (DEG/ENaCs). Tissue expression analysis revealed strong chemosensory organ specificity, with the highest number of highly expressed genes detected in the left cephalic tentacle, followed by the osphradium. Notably, pronounced left-right cephalic tentacle asymmetry was observed, with generally lower expression levels in the right cephalic tentacle, suggesting potential functional specialization of bilateral sensory organs. During developmental progression, over half of the ORs and IRs/iGluRs peaked at the fully mature stage, whereas a secondary expression peak was observed in juvenile individuals. An integrated examination of genes demonstrating high expression at the fully mature stage and in the left cephalic tentacle identified ten candidate genes, including five ORs, four IR/iGluRs, and one DEG-ENaC gene. This study systematically profiles putative olfactory genes across tissues and developmental stages in P. canaliculata, providing foundational insights into its chemosensation processes and providing a molecular resource for future studies of chemosensory function in this invasive species.