| Babylonia areolata,which is affiliated with the order mollusca Gastropoda,is of great economic value because of its many advantages,such as resistance to low oxygen,short breeding cycles,rapid growth and yield.Less research is currently available on the olfactory organs of B.areolata and the molecular mechanisms of their sensation.In this experiment,we investigated the effect of excision of olfactory organs on the feeding behavior of the B.areolata,and studied the microscopic and submicroscopic structures of tentacles and rhinophore by light and electron microscopy.Finally,q RT-PCR was used to analyze the distribution characteristics and expression of 13 candidate olfactory genes in tissues such as tentacles,rhinophore,mantle,gonads,gastrointestinal tract,liver pancreas and foot.The main results and conclusions were as follows:1.The removal of both tentacles and rhinophore affected the foraging behavior of the B.areolata,demonstrating that tentacles and water pipes play an important role in the feeding behavior of the B.areolata.B.areolata tentacles and rhinophore are covered with papillae,the surface layer is covered with microvilli,and the tip has cilia,the direction of cilia in tentacles is disordered,but the direction of cilia in rhinophore is more consistent;The antennae and rhinophore are important receptors,both with tactile and olfactory functions,and possess a special sensory epithelium,which is composed of three main types of cells: sensory cells,supporting cells and gland cells.In contrast to the single-layered columnar epithelium of tentacles,rhinophore have pseudo-complex ciliated columnar epithelium,and the two have large structural and functional differences,providing a theoretical basis for the identification of olfactory genes in shells.2.The 41 155 058 clean reads of tentacles and 46 464 642 clean reads of rhinophore were obtained and 89 091 unigenes were spliced,which were then compared to the protein database Nr using Blastx for Unigene sequences,yielding the highest similarity to Pomacea canaliculate.Followed by Aplysia californica and Elysia chlorotica,et al.Comparison by KOG database had 1785 genes functionally classified as signal transduction mechanisms.Comparison by the KEGG database yielded 57 genes as olfactory transduction metabolic pathways.Based on the Nr annotation information we used Blast2 GO software to get GO functional annotation,410 genes were G protein-coupled receptor signaling pathway involved in biological processes,19 genes were olfactory receptor active molecular functions.A total of 13 olfactory genes were screened and named as Baa OR1～Baa OR13.3.The distribution characteristics and expression of 13 candidate olfactory genes in tissues of B.areolata such as t tentacles,rhinophore,mantle,gonads,gastrointestinal tract,liver pancreas and foot,and speculation on the possible functions of Baa ORs in the chemical signal sensing process of B.areolata.Baa OR13 is specifically highly expressed in the tentacles,presumably with the primary function of detecting compounds that produce olfactory odors,thereby triggering nerve impulses that transmit information about the odor to the central nervous system;Baa OR6 and Baa OR8 are relatively highly expressed in gonads,and their functions are presumed to be mainly for spermatozoa to recognize their surroundings and achieve directional swimming toward the oocyte;Baa OR3,Baa OR9 and Baa OR10 are relatively highly expressed in the foot and have wound healing effects;Baa OR1,Baa OR7 and Baa OR12 have relatively high expression in Liver pancreas and are presumed to have a role in regulating lipid metabolism;Baa OR2,Baa OR4 and Baa OR11 are relatively highly expressed in the gastrointestinal tract and may have a role in regulating intestinal motility and digestion in the gastrointestinal tract.This study lays the molecular foundation for exploring the function of the olfactory receptor gene of the B.areolata and studying the mechanism of olfactory sensation in shellfish in depth. |
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