Revealing a genetic circuitry governing the development of the tritocerebral head segment

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In arthropods, homologous segments can have quite diverse morphologies. One particularly diverse segment is the head segment that gives rise to the tritocerebrum and has therefore been termed the tritocerebral segment. Depending on the arthropod clade, this segment carries diverse appendages - second-antenna in crustaceans or pedipalps in chelicerates - or has lost its appendages - intercalary segment of insects and myriapods. The loss, however, is phylogenetically independent and in both cases probably an adaptation to life on land. Moreover, the tritocerebral segment represents in all euarthropods the anterior-most segment expressing a Hox gene, which is usually responsible for segment specification. Within the iBeetle genome-wide RNAi screen we want to isolate a comprehensive set of genes involved in intercalary segment development of the red flour beetle Tribolium castaneum to understand the genetic circuitry specifying this segment. Moreover, we want to use this information then as reference point to ask functional questions on the evolutionary changes that led to the diversification and convergent evolution of the tritocerebral segment within the diverse arthropod clades.