Anatomical Structure Of The Central Nervous System Of Apolygus Lucorum(Hemiptera:miridae) And Antennal Pathways In The Central Nervous System

The mirid bug Apolygus lucorum(Meyer-Dur)(Hemiptera:Miridae)has become an important pest of cotton and fruit trees in the recent decades in China.The outbreak of A.lucorum was facilitated by the long-term adoption of transgenic Bacillus thuringiensis cotton in the large area in China.It is difficult to control the pest of A.lucorum,since it has the capacities of migration,diapause,rapid response,and high mobility among hosts in different seasons.The central nervous system of insect is an important center for regulating the behavioral and physiological activities.Therefore,it would be helpful to develop effective and green management techniques by investigating on the anatomical structures of the central nervous system and the neural basis that underlying the behavioral and physiological activities.The anatomical structure of the central nervous system of A.lucorum,however,has not been reported yet.In this study,immunohistochemistry,filling staining,confocal laster scanning microscopy,graphic processing,and three dimensional reconstruction were used to(1)examine the anatomical organization of the central nervous system of A.lucorum,(2)make the three dimensional reconstruction,(3)analyze the shape,volume,composition of each structure and their spatial relationship,(4)trace the pathway of the antennal sensory axons in the central nervous system.The main results are as follows:(1)The central nervous system of A.lucorum is composed of brain,gnathal ganglion,prothoracic ganglion,and the posterior ganglion.They are located in the head and thorax of A.lucorum.The brain is located between two compound eyes,dorso-posteriorly of head capsule,and above the esophagus.The gnathal ganglion is located ventral side of the body,under the esophagus.The prothoracic ganglion is located posteriorly to the gnathal ganglion.Brain,gnathal ganglion and the prothoracic ganglion are fused together forming a complex.The posterior ganglion is located in mesothorax,near the mesosternum,and linked to the prothoracic ganglion by a paired connective.There is no ganglion in the abdomen.Except the prothoracic ganglion,the ganglia of the central nervous system are high fused with several neuromeres.The brain of A.lucorum is constituted by 3 neuromeres:protocerebrum,deutocerebrum and tritocerebrum.The gnathal ganglion is composed of mandibular,'maxillary and labial neuromeres.The posterior ganglion is composed of mesothorax ganglion,metathorax ganglion and abdominal ganglion,while the abdominal ganglion is also composed of several abdominal neuromeres.All abdominal neuromeres form two parts:the anterior one and the posterior one which was name the terminal abdominal ganglion.In the front one,some structures like zipper and spiny trunk could be identified.The shape and location of the central nervous system is similar between female and male,but the volume is different.The volume of the central nervous system in female was bigger than that in male,which is corresponding to the volume of the body.In addition,the abdominal ganglion was also different in shape and volume between the male and female,which may be related to the difference of the shape and function of the reproductive organs in both sexes.(2)The structure of brain of A.lucorum is similar to that of other insects.The brain is composed of 3 constitutes:protocerebrum,deutocerebrum and tritocerebrum.In protocerebrum,several neuropils with clear boundary like optic lobes,mushroom bodies,central complex were distinguished.In deutocerebrum,two distinct neuropils,antennal lobe and antennal mechanosensory and motor center were identified.The tritocerebrum located ventrally,around the esophagus had very obvious boundary with the protocerebrum and deutocerebrum.Besides neuropils mentioned above,some structures like anterior optic tubercle,posterior optic tubercle,lateral accessory lobes were merger into midbrain with the large part of the unstructured protocerebrum.The relative volume of the midbrain to the whole brain is about 46%.(3)By means of neuronal backfills,histology,confocal microscopy,and three-dimensional reconstruction,we have studied the projection patterns of antennal sensory neurons in the central nervous system of this mirid and made the three-dimensional reconstruction model of the antennal lobe.The axons of the sensory neurons projected into the brain via the ipsilateral antennal nerve,and descended further into the gnathal ganglion,prothoracic ganglion,mesothoracic ganglion,and metathoracic ganglion,and reached as far as to the abdominal ganglion.These antennal pathways implied that the antenna have multiple functions.The antennal sensory axons were mainly project to the antennal lobe,which suggested that olfaction was the main function of the antenna of A.lucorum.The three-dimensional map of the antennal lobe of A.lucorum was established and 80 glomeruli were identified in the antennal lobe.