Homologous structures, exemplified by motoneurones of Mandibulata

Abstract

Studies of identified neurones at a distinct place within a species are required to understand how far variability or plasticity exert an influence on an individual structure. Primarily, such a study is independent of whether different profiles are attributed to genetic or epigenetic programs. Finally, the basic structure of the element in question should be constructed. This crucial structure, then, can be used for several approaches, which are based on the concept of the identified neurone: (1) Ontogenetical studies: addressing the question of when during ontogeny is this neurone present in its final (adult) form? (2) Homonomy (“serial homology”): addressing the question as to how far this element is reiterated along a segmented body. And, how far will the same genetic program be modified depending on the function of different segments? (3) Homology (in its classical sense): addressing the question, how far can a specific element be characterized in different species, thereby considering the different systematic levels of the animal kingdom? Is there a basic “Bauplan” of the nervous system that is valid for the various groups of Insecta, Tracheata, Mandibulata, Arthropoda?