Preliminary studies on rostrum development in the rice weevil, Sitophilus oryzae (Coleoptera: Curculionidae)

The study of developmental mechanisms, including appendage formation, in insects has been relatively limited to model organisms, namely Tribolium castaneum and Drosophila melanogaster. In beetles, Tribolium has been the primary model on which to study evolutionary developmental mechanisms; however, relatively recent additions include species of Onthophagus, which have emerged as new models for examination of horn development (Moczek and Nagy 2005; Moczek et al. 2006; Moczek et al. 2007). Although weevils are one of the most specious groups of organisms on the planet (ca. 60,000 species), and countless species are significant agricultural pests, not one weevil species has been utilized in developmental studies. Because the weevil rostrum is believed to represent a key innovation that has allowed the group to undergo an extraordinary radiation, one of the most obvious and interesting topics to address in studying the evolution of this group is the formation of the rostrum and how it has differentiated throughout the major weevil lineages. Due to a scarcity in knowledge about the fundamentals of rostrum growth (beginning in the late larval stages and traversing pre-pupal stages), this study has begun by investigating and documenting the morphological development of the rostrum using the rice weevil as a model.