Olfactory detection of ursodeoxycholic acid (UDCA) in large yellow croaker ( <i>Larimichthys crocea</i> ): responses, pathways and receptor functions

Olfactory communication plays a critical role in fish behavior and physiology, particularly in environments where visual and auditory signals are constrained. Bile acids, dual-function molecules serving as digestive agents and olfactory signals, are potent olfactory cues in aquatic ecosystems. The present study investigated the role of ursodeoxycholic acid (UDCA) as an olfactory attractant in large yellow croaker (Larimichthys crocea), an endangered species. Electrophysiological recordings demonstrated that UDCA elicits strong, concentration-dependent olfactory responses with a detection threshold of 10-12 mol l-1. Behavioral assays revealed UDCA-induced attraction exceeding that of other structurally similar bile acids, demonstrating significantly higher potency (P<0.05). Transcriptome analysis and pharmacological treatments revealed functional associations in UDCA detection. V2R1 upregulation and PLC pathway engagement (day 3) preceded delayed induction of OR11A1, TAAR13C-10 and OR52L2 with cAMP signaling (day 7), suggesting phased receptor involvement. Functional receptor expression assays confirmed that V2R1 mediates UDCA-induced calcium signaling, whereas OR11A1, TAAR13C-10 and OR52L2 respond through cAMP signaling. The present study provides a comprehensive understanding of UDCA chemosensation, linking receptor function, signaling pathways and behavioral responses. These findings enhance our understanding of fish olfactory systems and offer potential applications for species conservation and sustainable fisheries management.