The cellular and genetic mechanisms underlying the morphological diversity of insects
Allometric growth patterns have been extensively examined in post-embryonic stages of insects. Here, we characterized differential growth dynamics of hind legs during embryonic development of the house cricket, Acheta domesticus, and the milkweed bug, Oncopeltus fasciatus, two hemimetabolous species with a vast difference in the enlargement of the T3 legs. We found that Acheta exhibits a significant variation in size between the T2 and T3 legs only after the segments become clearly visible. In contrast, a much smaller percentage of the T3 leg enlargement occurs in Oncopeltus, and it is similar at the end of the initial (before segmentation) and final (after segmentation) stages of embryogenesis. Additionally, we determined the cellular mechanisms underlying the allometric leg growth by measuring the relative mitotic activity (RMA), a ratio of proliferating cells to total leg length. During the initial phase of embryogenesis, Acheta shows an increasing trend in RMA, however the RMA decreases in Oncopeltus as development proceeds. The mitotic activity ceases completely in both species during the final stage of development, while legs continue to