Organisation of the thoracic ganglia of the adult sphinx moth Manduca sexta (Insecta, Lepidoptera)

Abstract

The present work describes the neuroanatomy of the thoracic ganglia in the adult sphinx moth Manduca sexta from transverse, horizontal and sagittal sections in order to provide a basis for a more precise description of identified neurons and their connections within the thoracic ganglia. The prothoracic ganglion of M. sexta derives from a single neuromere, whereas the pterothoracic ganglion results from the fusion of the meso- and metathoracic and the first and second abdominal neuromeres. Each hemiganglion contains nine longitudinal tracts (MDT, LDT, DMT, DIT, VLT, VIT, LVT, MVT and VMT) and six dorsal (DC I–VI) and five ventral commissures (VC I, dVCL II, vVCL II, SMC and PVC). Additionally there are vertical or oblique tracts such as the T-tract, C-tract or I-tract. The ring tract could not be found, LDT, DIT, DMT and MVT1 are compact and well defined, whereas VMT and MVT and also VLT and VIT are difficult to separate in many sections. MDT and especially LVT are quite inconspicuous in transverse sections. In horizontal or sagittal sections it is much easier to identify these tracts. As in Locusta migratoria and Carausius morosus, the second dorsal commissure (DC II) is subdivided. DC IV and DC V are difficult to separate in all cutting planes. The results are compared with published data of other insects. The present work supports the hypothesis of a common basic pattern of all insect ganglia.