Central Projections Of Antennal And Labial Palp Seneory Neurons And 3D Atlas Of The Antennal Lobe Glomerulis In Corcyra Cephalonica

The brain is the center for regulating insect behavior,and the antennal lobe is an important part of the insect brain for processing olfactory information.When the sensory neurons in the antennae or labial palps perceive external stimuli,they transmit these signals along the axons to the brain,where the input information is processed and integrated by the antennal lobes inside the brain,leading to specific behavioral commands,such as foraging,locating hosts,identifying mates,selecting egg-laying sites,and avoiding dangerous.Therefore,studying the projection pathways of insect antennal and labial palp neurons and the anatomical structure of the antennal lobe of the brain can provide an anatomical basis for analyzing the information processing mechanism of the central nervous system of insects,which can help to guide the development of green control technologies at the olfactory level.The rice moth（Corcyra cephalonica）belongs to the family Galleriinae of Lepidoptera and is a widespread and destructive storage pest that can damage a variety of stored products and processed foods,and has long threatened the development of food security and food processing industries.Till now,there are relatively few studies on the structural functions of the central brain and the regulatory mechanisms of the nervous system in storage pests.In this study,we used laser confocal microscopy,immunohistochemical fluorescence staining and labeling methods,and computerized three-dimensional reconstruction techniques to clarify the projection pathways of sensory neurons in the brain of the antennae and labial palp of female and male adult rice moths,and to reconstruct the three-dimensional structure of the antennal lobes.The main results of this study are as bellow:（1）There are three main projection pathways of antennal sensory neurons in the brain of rice moths,namely,antennal lobe projections,antennal mechanosensory and motor center projections,and gnathal ganglion projections.The tracer analysis of the neural projection pathways within the unilateral tentacles of rice moths using tentacle backfill staining showed that after entering the midbrain,a large number of nerve endings of rice moth tentacle sensory neurons terminated in the ipsilateral antennal lobes and antennal mechanosensory and motor centers,with some nerve fibers projecting to the gnathal ganglion and very few nerve fibers projecting to the forebrain.Both female and male adults projected unilaterally,with no significant differences in projection areas.This multiple projection pattern may play an important role in the integration of olfactory information transmission,antennal motor regulation,foraging and learning activities in rice moths.（2）There are three projection pathways for the sensory neurons of the labial palp,namely,the antennal lobe projection,the antennal mechanosensory and motor center projection,and the gnathal ganglion projection.The tracing analysis of the unilateral neural projection pathway within the lower labial whiskers of the rice moth,using lower labial whisker backfill staining,showed that the lower labial whisker neurons of the rice moth first entered the gnathal ganglion,then passed through the antennal mechanosensory and motor centers,and finally terminated in the peripheral olfactory bulb of the antennal lobe.The male moths project unilaterally,while females project bilaterally and specifically to a single olfactory bulb located ventrally in the antennal lobe-labial-palp pit organ glomerulus（LPOG）.This multiple projection pattern may be related to the feeding behavior of rice moths,while the difference between males and females may be related to the perception of CO₂concentration in the external environment by females,which in turn affects their choice of oviposition sites.（3）The rice moth adults have sexual dimorphism in their antennal lobes.Three-dimensional reconstruction and identification of the antennal lobes of female and male moths using Amira 5.4.0 showed that males had 52 olfactory glomeruli with a surface area of531278.0±47631.0μm²and a volume of 19332299.6±669415.0μm³（mean±SD,n=5）and an expanded fibrillar The female had 41 olfactory glomeruli with a surface area of935078.6±134713.0μm²and a volume of 9436276.7±747304.7μm³（mean±SD,n=5）,and a specific glomerulus,LPOG,on the ventral side of the antennal lobe,with a surface area of 34606.4±2020.7μm²and a volume of 38033.6±669415.0μm³（mean±SD,n=5）.In conclusion,the study of the neural projection pathways of the antennal and labial palp and the three-dimensional reconstructed structures of the antennal lobes of rice moths can provide a structural basis and a theoretical basis for the in-depth study of the olfactory mechanism of rice moths,provide an anatomical reference for the study of the brain structure of other lepidopteran insects,especially storage pests,and lay the foundation for the prevention and control of rice moth populations by regulating their feeding or egg-laying behaviors in the future,and have potential value for the prevention and control of rice moths and other storage pests.It has indirect potential value for the prevention and control of rice moths and other storage pests.