A Genomic Survey of SCPP Family Genes in Fishes Provides Novel Insights into the Evolution of Fish Scales

The family of secretory calcium-binding phosphoproteins (SCPPs) have been considered vital to skeletal tissue mineralization. However, most previous studies focused on phylogenetically distant animals but not on those closely related species. Here we provide novel insights into the coevolution of genes and fish scales in 10 species from . According to their scale phenotypes, these fishes can be divided into three groups, i.e., scaled, sparsely scaled, and scaleless. We identified homologous genes in the genomes of these species and revealed an absence of some members in some genomes, suggesting an uneven evolutionary history of genes in fishes. In addition, most of these genes, with the exception of , individually form one or two gene cluster(s) on each corresponding genome. Furthermore, we constructed phylogenetic trees using maximum likelihood method to estimate their evolution. The phylogenetic topology mostly supports two subclasses in some species, such as , , , and , but not in the other examined fishes. By comparing the gene structures of recently reported candidate genes, and , for determining scale phenotypes, we found that the hypothesis is suitable for , but denied by , even though they are both sparsely scaled for cave adaptation. Thus, we conclude that, although different fish species display similar scale phenotypes, the underlying genetic changes however might be diverse. In summary, this paper accelerates the recognition of the family in teleosts for potential scale evolution.