Topographic anatomy of ascending and descending neurons of the supraesophageal, meso- and metathoracic ganglia in paleo- and neopterous insects

Abstract

Topographic anatomy of ascending (AN) and descending (DN) neurons of the supraesophageal and thoracic ganglia in the nervous system of winged insects (Pterygota) - representatives of infraclasses Plaeoptera (Odonata, Aeschna grandis, dragonfly) and Neoptera (Blattoptera, Periplaneta americana, cockroach) was studied. These insects are different in ecological niches, lifestyles, sets of behavioral complexes, levels of locomotor system development, evolutionary age and systematic position. Neuronal bodies and processes of ANs and DNs were stained with nickel chloride (NiC2), their topography was studied on total prerapations of the supraesophageal and thoracic ganglia. Unlike cockroaches, in dragon- fly protocerebrum DNs sending their processes to ocelli were found. Dragonfly DN processes show a spe- cific type of arborization in thoracic ganglia, with collaterals directed both ipsi- and contralaterally. In cockroaches collaterals of DN processes are arranged ipsilaterally. AN bodies in meso- and metathoracic ganglia of dragonfly lie both ipsi- and contralaterally in respect to the ascending process whereas in cock- roaches AN bodies in the same ganglia are predominantly localized contralaterally. Substantial differences in allocation of DNs and ANs in insects dissimilar in locomotor manner reflect a different extent of supraesophageal ganglion control over activity of segmental centers. It seems related to neither the evolu- tionary age of insects, nor the antiquity of origin, nor their systematic position. Probably, a different de- gree of locomotion control depends on the way of getting food - catching prey in air by <<paleopterous>> dragonflies unlike <<simple>> maneuverable walking or running across a solid substrate by <<neopterous>> cockroaches.