|
Figure 1
Short
germ band insects. (A) The posterior proliferation zone of the Petrobius,
a wingless thysanuran. The germ band gives rise to the anterior head, while
the posterior proliferation zone (dark stipples) continues to divide to
provide cells for the posterior head, thorax, and abdominal segments. (B)
In situ hybridization of engrailed shows the segmentation of the
short germ band beetle, Tribolium. The left shows an early stage
when only the gnathal (jaw, G1) segment has been laid down by the posterior
zone of proliferation. The center figure shows a later stage where thoracic
(T) and abdominal (A) segments have also been made. The right figure is
at the end of segmentation, and the brain (br) antennal segment (ant) and
intercalary (int) segment are differentiating. (A after Anderson, 1973 and
Gerhart and Kirschner, 1997; B after Sulston and Anderson, 1996). |
