Gene Silencing via Embryonic RNAi in Spider Embryos.

INTRODUCTIONThe spider Cupiennius salei, commonly known as the American wandering spider, is a particularly useful laboratory model for embryological studies because of the availability of tools to study and manipulate its embryonic development. Cupiennius is used to study axis formation, segmentation, appendage development, neurogenesis, and silk production. These studies contribute to our understanding of the evolution of these processes, but they also help us to understand the origin and diversification of evolutionary novelties. Comparisons between spiders and insects can show the degree of conservation and divergence of developmental mechanisms during arthropod evolution. Any embryological feature conserved between spiders and insects is likely to represent an ancestral feature for arthropods. Comparative molecular embryological work in insects and spiders should eventually allow us to define a molecular archetype for the phylum Arthropoda. This in itself will be a necessary cornerstone for comparing the different metazoan phyla, including chordates. The discovery of RNA interference (RNAi), in which double-stranded RNA (dsRNA) suppresses the translation of homologous mRNA, has had a huge impact on evolutionary developmental biology by enabling the analysis of loss-of-function phenotypes in organisms in which classical genetic analysis is laborious or not possible. This protocol describes the application of RNAi to embryos of the spider C. salei.