Evolution and development of spiders' spinnerets (Arachnida: Araneae)

Abstract

The spinnerets are an important synapomorphy of spiders, and together with silk they allow them to build their webs. This unique feature of spiders constitute one of the main factors responsible for the ecological success and conquest of nearly every terrestrial habitats, and their current diversity. The morphology of spinnerets is widely used in phylogenetic reconstructions and to classify important groups within Araneae. However, molecular mechanisms and genes involved in the development of the spinnerets are not clear hitherto. Thus, we will pursue two main biological questions: (i) the presence/occurrence of rapid changes in the coding sequences of genes involved in morphological innovations in a phylogenetic context in the order Araneae and (ii) the role of regulatory changes in the transverse arrangement of spinnerets in spiders of the Hahniidae family. We expect that, by using these two different approaches, we will reveal the relative contribution of structural changes, and cis and trans regulatory effects in the morphology of spinnerets in Araneae. Furthermore, the investigation of patterns of genome wide gene expression and evolution could indicate which genes are involved in the development of spinnerets, and which evolutionary mechanisms underlie the observed patterns. Candidate genes will be selected from the genome-wide analyses and studied further to establish causal relationships between gene sequence and expression and the development of spinnerets. (AU)