Fig. 1

Thamnocephalus development and morphometric measures. a–c En protein staining in larvae with a three thoracic En stripes, b six thoracic En stripes, and c eight thoracic En stripes. Asterisks mark the first thoracic segment in each larva (the two stripes visible anterior to this are the first and second maxillary segments) and in c show the outpocketing of the segmental limb bud from the body wall. In b, c white arrow point to scanning electron micrographs of similarly staged larvae. d Thamnocephalus larva illustrating measurements used in this study (defined in “Materials and methods”): 1—body length, 2—growth zone length, 3—growth zone width “A” (width of newly added En stripe), 4—growth zone width “B”, 5—ventral trunk area, 6—ventral area of last segment, 7—ventral growth zone area, 8—last segment length. Note, the area measures are in color; length measures are given in white and denoted with an arrowhead. Scale bar = 100 μm. En expression (red). All larvae are shown with anterior to the left, ventral side up