Background: Olfaction plays a central role in mating, spawning, obtaining food and escaping predators, which is essential for survival and reproduction of animals. The nature of the olfactory perception in crabs, which is a major group of crustaceans, has remained elusive.
Objective: This project aims to explore the molecular mechanism of olfaction in crabs and further improve our understanding of olfactory perception in crustaceans.
Methods: The olfactory receptors and ingestion-related gene expression in Eriocheir japonica sinensis were studied by transcriptomic techniques. The de novo assembly, annotation and functional evaluation were performed with bioinformatics tools.
Results: A series of chemosensory receptors associated with olfaction were identified including 33 EsIRs, 24 EsIGluRs, 58 EsVIGluRs, 1 EsOR and 1 EsGC-D. We found IRs were key odorant receptors demonstrating a specific species evolutionary trend in crustaceans. Furthermore, we identified ORs in E. j. sinensis and Litopenaeus vannamei. The incomplete EsOR and LvOR1 structures implied that ORs exist in crustaceans, and may have been degenerated or even lost in the olfactory evolutionary process. In addition, comparative transcriptome analysises demonstrated two possible olfactory transduction pathways of E. j. sinensis: the cGMP-mediated olfactory pathway related to vegetable odor molecules and the cAMP-mediated olfactory pathway related to meat odor molecules. The above results were consistent with its omnivorous ingestion of E. j. sinensis.
Conclusions: Our study revealed the unique olfactory molecular mechanism of omnivorous crabs and provided valuable information for further functional research on the chemoreception mechanisms in crustaceans.
Keywords: Antennules; Chinese mitten crab; Molecular mechanism; Olfaction; Transcriptome sequencing.