Investigating the effect of limb-patterning genes on the development of mandibular outgrowths in weevils (Coleoptera: Curculionidae)

The morphology of insect mouthparts plays an essential role in fitness and survival; as a result, diverse forms have arisen which impart advantages in utilizing alimentary resources. Prior study has investigated the role of three gap genes responsible for limb-patterning processes, Distal-less (Dll), dachshund (dac), and homeothorax (htx), in mouthpart development in the dung beetle Onthophagus taurus, yet no further work has been carried out on the impact these genes may have in other groups of insects. In this work, the development of the distinctive and apomorphic rostrum of weevils is analyzed in response to RNAi knockdowns of the Dll, dac, and htx genes through the utilization of two species: the citrus root weevil, Diaprepes abbreviatus and the rice weevil, Sitophilus oryzae. In particular, the deciduous mandibular outgrowths of the citrus root weevil are analyzed to ascertain the role gap genes play in the formation of extra-mandibular processes and rostrum development is contrasted between the two weevil species to elucidate whether pathways are shared in the formation of mouthparts  in this coleopteran lineage.