The evolution of arthropod segmentation: insights from comparisons of gene expression patterns.

The comparison of gene expression patterns in a number of insect and crustacean species has led to some insight into the evolution of arthropod patterning mechanisms. These studies have revealed the fundamental nature of the parasegment in a number of organisms, shown that segments can be generated sequentially at the molecular level, and suggested that pair-rule pre-patterning might not be shared by all insects.