Characterization of morphological development and olfactory receptor genes in the olfactory system of red-eared slider (Trachemys scripta elegans).

Previous behavioral studies have confirmed that the globally invasive red-eared slider (Trachemys scripta elegans) exhibits acute chemical sensitivity and a preference for heterosexual odor cues. However, the integrated developmental characteristics of its olfactory system and the key genes responsible for this specific chemical perception remain limited. We systematically analyzed the morphological structures of the nasal cavity and olfactory bulb across three developmental stages (juvenile, subadult, and adult), characterized the olfactory receptor (OR) gene repertoire, and identified differential expression patterns of key OR-related signaling molecules. Morphometric analysis revealed that the olfactory region consistently occupied over 58% of the total nasal cavity volume across all groups, indicating a central ecological role for olfaction throughout the life cycle. Genomic data showed that this species possessed 727 functional OR genes and 55 pseudogenes. This conserved and sizable genomic architecture likely underlies its chemical perception and environmental adaptation. qRT-PCR analysis demonstrated a significant developmental upregulation of olfactory marker protein (OMP), indicating continuous refinement of the olfactory neural circuitry. Notably, we found that the olfactory system primarily relied on the OR pathway, and multiple olfactory-related genes, including the OR genes OR52E4, OR51G1, OR51G2, OR52R1, OR52P1 as well as V2R, were specifically upregulated in adult males, implying their potential involvement in recognizing male-specific chemical cues, such as those used in courtship. However, the precise functions of these genes require further validation. In summary, the findings lay a solid foundation for elucidating the functional differentiation and ligand recognition mechanisms of chemosensory receptor genes in T. s. elegans.