The morphology of the antennal lobe of Ambrostoma quadriimpressum(Coleoptera:Chrysomelidae)

The structure of the primary olfactory brain center was studied in male and female adult Ambrostoma quadriimpressum by means of a series of histological sections labeled using the reduced-silver-stain technique.The antennal lobe was elliptical,and the total number of glomeruli was approximately 50 in the antennal lobe in both sexes.There was no sexual dimorphism with respect to the size of the antennal lobe or the number and shape of glomeruli.

Glomerular organization in the antennal lobe of the oriental armyworm Mythimna separata

In insects,the number and specificity of antennal lobe glomeruli often reflect the number and diversity of expressed chemosensory genes,which are linked to its ecological niche and specific olfactory needs.The oriental armyworm,Mythimna separata,is an important and common lepidopteran pest of cereal crops.Given its reliance on the olfactory system for crucial behaviors,understanding the evolutionary potential of this system requires a thorough characterization of the anatomical structure of the primary olfactory center.Here,we systematically identified all antennal lobe glomeruli of M.separata based on synaptic antibody immunostaining and mass staining of the olfactory sensory neurons.A total of 69 glomeruli were identified in females and 65 in males,and an intuitive nomenclature based on glomerular positions was applied.Our findings uncovered some sex-specific glomeruli in this species.There were ten female-specific glomeruli and three male-specific glomeruli,except for the macroglomerular complex(MGC)units,with a notable observation that the female labial pit organ glomerulus was larger than its male counterpart.Additionally,we identified four antennal-lobe tracts(ALTs)and retrograde labeling from the calyx revealed that all glomeruli were innervated by the medial ALT projection neurons.The comparison of the olfactory system structures between M.separata and sympatric moths supports their evolutionary convergence in noctuid moths.These results collectively lay the foundation for future studies on olfactory processing in M.separata.

Three-dimensional structure of the antennal lobe in the Southern house mosquito Culex quinquefasciatus

The Southern house mosquito Culex quinquefasciatus relies on its olfactory system to locate the human hosts for blood meals,by which several deadly diseases are transmitted.Olfactory sensory neurons(OSNs)housed in the sensilla on the olfactory appendages send their axons into the antennal lobes(ALs),the primary olfactory center in the brain,where the OSNs expressing the same olfactory receptors converge upon the same spherical structures known as glomeruli in the AL.The structure of the antennal lobe,that is,the spatial organization of the glomeruli,governs the insect's odor identification and discrimination.Drosophila studies have demonstrated the specific connections between receptors and glomeruli based on the 3D structure of the antennal lobe,deepening our understanding of the relationships between glomerular activities and behaviors,but as yet the structure of the Cx.quinquefasciatus antennal lobe remains unknown.We therefore constructed a 3D model of the Cx.quinquefasciatus antennal lobe using nc82 antibody staining,identifying 62 and 44 glomeruli in the female and male mosquito antennal lobe,respectively,with a significant sexual dimorphism in terms of the antennal lobe volume and glomerulus number.These results demonstrate the structural basis of mosquito odor coding and provide a platform for future studies of the mosquito olfactory signal processing mechanism.