Commissural organisation and brain segmentation in insects

TY - CHAP

T1 - Commissural organisation and brain segmentation in insects

AU - Boyan, George

AU - Williams, L

AU - Hirth, Frank

PY - 2007/1/1

Y1 - 2007/1/1

N2 - Recent molecular data obtained in grasshopper and Drosophila suggest that the anterior insect brain comprises three neuromeres: (1) the protocerebrum (PC); (2) the deutocerebrum (DC); and (3) the tritocerebrum (TC). In contrast to embryonic neuromeres in the ventral nerve cord (VNC) each of which possess two commissures, the PC and TC only possess one, while the DC does not appear to possess a commissure at all. A reason for this asymmetry is likely to be the presence of the stomodeum, which exerts a profound influence not only on the gross morphology of the developing brain, but also, as an inductive factor, on its axon scaffold. Immunocytochemical and anatomical studies in embryonic and adult grasshopper and Drosophila suggest that deutocerebral neurons project commissural axons across the midline in association with both the protocerebral and tritocerebral commissures (TCC). This implies that the foregut bisects the brain topologically within the DC itself and not, as traditionally thought, between the DC and the TC. Genetic experiments in Drosophila appear to confirm these anatomical observations and provide evidence for different regulatory mechanisms being responsible for commissure formation in the anterior insect brain as opposed to the VNC.

AB - Recent molecular data obtained in grasshopper and Drosophila suggest that the anterior insect brain comprises three neuromeres: (1) the protocerebrum (PC); (2) the deutocerebrum (DC); and (3) the tritocerebrum (TC). In contrast to embryonic neuromeres in the ventral nerve cord (VNC) each of which possess two commissures, the PC and TC only possess one, while the DC does not appear to possess a commissure at all. A reason for this asymmetry is likely to be the presence of the stomodeum, which exerts a profound influence not only on the gross morphology of the developing brain, but also, as an inductive factor, on its axon scaffold. Immunocytochemical and anatomical studies in embryonic and adult grasshopper and Drosophila suggest that deutocerebral neurons project commissural axons across the midline in association with both the protocerebral and tritocerebral commissures (TCC). This implies that the foregut bisects the brain topologically within the DC itself and not, as traditionally thought, between the DC and the TC. Genetic experiments in Drosophila appear to confirm these anatomical observations and provide evidence for different regulatory mechanisms being responsible for commissure formation in the anterior insect brain as opposed to the VNC.

U2 - 10.1016/B0-12-370878-8/00150-6

DO - 10.1016/B0-12-370878-8/00150-6

M3 - Chapter

SN - 978-0-12-370878-6

VL - 1

SP - 349

EP - 359

BT - Evolution of Nervous Systems

A2 - Bullock, TH

A2 - Krubitzer, L

A2 - Preuss, T

A2 - Rubenstein, J

A2 - Strausfeld, N

A2 - Streidter, G

PB - Elsevier publishing company

CY - London, San Diego

ER -