Neuronal fiber tracts connecting the brain and ventral nerve cord of the early Drosophila larva

Abstract

Using a combination of dye injections, clonal labeling, and molecular markers we have reconstructed the axonal connections between brain and ventral nerve cord of the first instar Drosophila larva. Out of the approximately 1400 neurons that form the early larval brain hemisphere, less than 50 cells have axons descending into the ventral nerve cord. Descending neurons fall into four topologically defined clusters located in the antero-medial, antero-lateral, dorsal, and baso-posterior brain, respectively. The antero-lateral cluster represents a lineage derived from a single neuroblast. Terminations of descending neurons are almost exclusively found in the anterior part of the ventral nerve cord, represented by the gnathal and thoracic neuromeres. This region also contains small numbers of neurons with axons ascending into the brain. Terminals of the ascending axons are found in the same basal brain regions that also contain descending neurons. We have mapped ascending and descending axons to the previously described scaffold of longitudinal fiber tracts that interconnect different neuromeres of the ventral nerve cord and the brain. This work provides a structural framework for functional and genetic studies addressing the control of Drosophila larval behavior by brain circuits.

Information flow through neural circuits for pheromone orientation

“…Insects have several hundred DNs that connect the brain and ventral nerve cord [31][32][33] . We performed backfill labelling from the cut end of the neck connective, and the cell bodies of approximately half of the DNs were located in the supraesophageal ganglion (Fig.…”

“…Descending pathway through the LAL is likely to be common across insects [15][16][17][18][31][32][33] . Our results not only demonstrate an example of a series of neural circuits dedicated for moth olfactory navigation, but also provide insights into the general design of neural circuits for sensory-motor control in insects.…”

Associative learning between odorants and mechanosensory punishment in larval Drosophila

“…This seems timely as mechanosensation is rather well analysed (Jarman, 2002;Kernan, 2007;Lumpkin et al, 2010;Yin and Kuebler, 2010;Wu et al, 2011), including attempts to identify firstand second-order interneurons (Smith and Shepherd, 1996;Diegelmann et al, 2008;Cardona et al, 2009). Also, from a practical point of view, temporal control over mechanosensory stimulation can be much finer grained than is the case for gustatory reinforcement in the larva, where tastants have to be added to the substrate and therefore changes in substrate necessarily involve translocation of the animals.…”

Development of the anterior visual input pathway to the Drosophila central complex

“…The LAL has been long recognized as a major output region of the protocerebrum that projects towards motor centers in the subesophageal and thoracic ganglia (Namiki & Kanzaki, ). Long projection neurons with arborizations in the LAL can be backfilled when applying tracer molecules to the VNC (Cardona, Larsen, & Hartenstein, ). In the adult brain, neurons of lineage DALd possess the exact same structure (Wong et al, ), and we speculate that primary neurons of the DALd lineage have a similar projection (Figure a, b).…”