Fig. 3

The evolution of opsin diversity and photoreception tuning in C. farreri. a Morphology of scallop eyes scattered along the edge of mantles (left, scale bar: 1 cm), schematic structure of a typical scallop eye (middle), and expression of diverse opsin genes in scallop eyes (right). Eye samples from three individuals were used in expression evaluation with standard error shown for eye and mantle groups. The asterisks indicate genes showing significantly higher expression in eyes than in the mantle (p-value < 0.05, the exact test by edgeR). b R-opsin gene structures of Mollusca and Branchiopoda. Exons rather than introns were plotted in proportion, with scale bar representing 500 bp. NETR (neurotrypsin) and FPV246 (putative ankyrin repeat protein) are the conserved neighboring genes. c Sequence similarity and Ka/Ks values of all opsin genes between the scallops of C. farreri (CF) and P. yessoensis (PY). These data were calculated based on full protein sequences. The black line insides the box indicates the median value, and the whiskers extend from the first or third quartiles to the minimum or maximum values. d Bivalve opsin phylogeny and variation at key functional sites sensitive to various light ranges. Species abbreviations: Chlamys farreri (CF), Pinctada fucata (PF), Crassostrea gigas (CG), Argopecten irradians (AI), Patinopecten caurinus (PC) and Argopecten purpuratus (AP). Site combinations of “SFA,” “GFA” and “AFA” above the major branches are the putative ancestral bivalve types deduced from extant species. Colors of the sites correspond to the colors or wavelengths of opsin sensitivity in human opsins