CORRELATION BETWEEN DISTAL-LESS EXPRESSION PATTERNS AND STRUCTURES OFAPPENDAGES IN DEVELOPMENT OF THE 2-SPOTTED CRICKET, GRYLLUS-BIMACULATUS

A million of insect species have been identified so far, displaying a staggering variety of adult morphologies. To elucidate mechanism how s uch insect morphologies are developed at a molecular level, we investi gated developmental process of the two-spotted crick:et, Gryllus bimac ulatus, as a typical hemimetabola, and compared with that of Drosophil a as an extensively studied typical holometabola. We analyzed expressi on patterns of homeobox genes of engrailed (en) and Distal-less (Dll) during development. In early embryos, an is expressed in the posterior compartments of body segments and developing appendages, while Dll is expressed in the distal region corresponding to the telopodite of dev eloping appendages. Interestingly, these expression patterns are very similar to those observed in Drosophila imaginal discs. In the case of Dll, we found that its expression pattern, which is similar to each o ther in various appendages at early stages, changes in progress with e longation and segmentation, depending on the type of appendages. Late expression patterns of Dll are classified into three types: Dll expres sion in the entire region of the antenna, in a distal region of the ce rcus, and in distal and middle regions of the leg, maxillary and labia l palpus, indicating that Dll expression patterns are closely related to segmentation patterns of the appendages. Furthermore, since Dll is intensely expressed in both sides of the femur-tibia articulation of t he leg, we considered that Dll is involved in positioning of articulat ion during the late appendage development. Hence, our results indicate d that although common molecules are involved in development of insect appendages, the variety of the morphologies depends on pattern and ti ming of their expressions.