Insect evolution: filling in the gaps Available to Purchase

In the long germband insect Drosophila, all of the body segments are specified simultaneously, but most insects undergo `short' or `intermediate' germ segmentation in which the anterior and posterior segments are specified at different times. In Drosophila, gap genes both specify, and provide identity to, several contiguous segments, so what is their function in short/intermediate-germband insects? On p. 835, Paul Liu and Nipam Patel report that the homolog of the Drosophila gap gene giant in Oncopeltus fasciatus (an intermediate germband insect) is a bona fide gap gene. RNAi knockdown of Oncopeltus giant, they report, results in deletion of the maxillary and labial segments and of the first four abdominal segments. By contrast, previous work indicates that in Tribolium castaneum, a short germband beetle, giant controls gnathal (jaw) segment identity, rather than its formation, and is required for the segmentation of the entire abdomen. Liu and...