Gr. Steffens et W. Kutsch, HOMONOMIES WITHIN THE VENTRAL MUSCLE SYSTEM AND THE ASSOCIATED MOTONEURONS IN THE LOCUST, SCHISTOCERCA-GREGARIA (INSECTA, CAELIFERA), Zoomorphology, 115(3), 1995, pp. 133-150
To understand the segmental reiteration of an insect, the serially arr
anged neuromuscular system of the locust, Schistocerca gregaria, is st
udied. The ventral muscle system is chosen and its motoneuronal supply
is described in the thoracic and pregenital segments. In general, rep
etitively arranged, similar sets of motoneurons (MNs) supply the ventr
al muscles of these segments. Common criteria of both topology of musc
les and neural features (nerve branches and motoneuronal supply) sugge
st possible homonomies of the ventral longitudinal muscles and ventral
diaphragm of the thoracic and abdominal system. Based on a segment-by
-segment analysis, muscle topology and motor supply match, in most ins
tances. There are, however, cases where such a parallelism is missing.
In a particular case the supply of apparently homonomous muscles shif
ts from one set of MNs to another. In another case, putatively equival
ent MNs of different ganglia supply morphologically different muscle s
tructures in the adult animal. Therefore, it becomes apparent that mus
cles and their supplying MNs are, in principle, independent elements w
hich might be subjected autonomously to ontogenetic processes. As a co
nsequence, in the search for the basic segmental Bauplan depending on
homonomous structures, muscles and MNs have to be regarded as separate
entities.