The presence of cellular cartilage-like tissues outside the chordate lineage is either indicative of a common origin of cartilage as a metazoan tissue type (homology), or alternatively highlights developmental and/or structural constraints in constructing an internal cellular support tissue or endoskeleton (convergence). If a genetic program for specifying chondrocytes (cartilage cells) arose only once during metazoan evolution, there should exist a molecular fingerprint that is common amongst all lineages, despite their long independent evolutionary history. The alternate hypothesis is that cartilages found within invertebrate groups are unrelated, and thus a common molecular fingerprint would not be expected. The current study is aimed at distinguishing between these two alternatives through molecular characterization of the regulation and specification of chondrocytes in the cephalopod mollusk, Sepia officinalis. The specific objectives of this study include: 1) analysis of candidate genes involved in vertebrate chondrogenesis in the context of Sepia development. 2) identification of novel genes involved in cephalopod chondrogenesis with particular focus on transcription factors. 3) functional analysis of identified genes of interest through the use of RNA interference during Sepia development. 4) characterization of the role of any novel cephalopod genes in vertebrate chondrogenesis using the zebrafish, Danio rerio.