Expression and function of the zinc finger transcription factor Sp6–9 in the spider Parasteatoda tepidariorum
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. This protocol describes the collection and fixation of embryos from C. salei. The fixed embryos can be stored at -20°C for prolonged periods and used for in situ hybridization, in studies of apoptosis using terminal deoxynucleotidyl-transferase-mediated dUTP-digoxigenin nick-end labeling (TUNEL), and for immunohistochemistry.