The sensory shark: high-quality phenotypic, genomic and transcriptomic data for the small spotted catshark Scyliorhinus canicula reveal the molecular bases of sensory organ evolution in jawed vertebrates

Cartilaginous fishes (chimeras and elasmobranches -sharks, skates and rays) hold a key phylogenetic position to explore the origin and diversifications of jawed vertebrates. Here, we report reference genomic, transcriptomic and phenotypic data in the small spotted catshark Scyliorhinus canicula , and integrate these data to shed light on the evolution of sensory organs. We first characterise general aspects of the catshark genome, confirming the high conservation of genome organisation across cartilaginous fishes, and investigating population genomic signatures. Taking advantage of a dense sampling of transcriptomic data, we also identify gene signatures for all major organs, including chondrichthyan specializations, and evaluate expression diversifications between paralogs within major gene families involved in sensory functions. Finally, we combine these data with 3D imaging and in situ gene expression analyses to explore chondrichthyan-specific traits and more general evolutionary trends of sensory systems. This approach brings to light, among others, novel markers of the ampullae of Lorenzini electro-sensory cells, a duplication hotspot for crystallin genes conserved in jawed vertebrates, and a new metazoan clade of the Transient-receptor potential (TRP) family. These resources and results, obtained in an experimentally tractable chondrichthyan model, open new avenues to integrate epigenomics, single-cell and spatial transcriptomics, for the study of elasmobranchs and vertebrates. ### Competing Interest Statement The authors have declared no competing interest.