DEVELOPMENT OF LOCUSTATACHYKININ IMMUNOPOSITIVE NEURONS IN THE CENTRAL COMPLEX OF THE BEETLE TENEBRIO-MOLITOR

Locustatachykinin-immunoreactive (LomTK-IR) interneurons were found to be associated with the central complex, a prominent neuropil region o f the insect brain. The structures and development of this set of brai n interneurons was studied from the embryo onward in the beetle Tenebr io molitor, showing individual neurons that persist from the late embr yo to the adult stage. Their essential structural characteristics were already present in the late embryo, but distinct parts of their arbor ization patterns became newly formed throughout development. Using a c ombination of immunohistochemistry and single-cell injection, we demon strated minute structural changes, allowing a characterization of stru ctural plasticity of identifiable, persistent, neuropeptidergic neuron s throughout ontogenesis. Furthermore, this study has provided new inf ormation about basic principles of central brain neuroanatomy and the development of a distinct midbrain region of the insect brain, the cen tral complex. The development of its basic connections, the connection s between the fan-shaped body and the protocerebral bridge, and the co mpartmentation of these neuropil regions were shown, using LomTK-IR ne urons as marker structures. These basic features of the central comple x-associated LomTK-immunopositive neurons were formed in the embryonic brain, whereas in metamorphosis, reorganization of these persistent i nterneurons was restricted to the formation of a precisely defined pro jection of their side branches. (C) 1996 Wiley-Liss, Inc.