The genetic basis of scale-loss phenotype in the rapid radiation of Takifugu fishes

The genetic basis of scale-loss in Takifugu pufferfishes
 Abstract Rapid radiation associated with phenotypic divergence
and convergence provides an opportunity to study the genetic mechanisms of
evolution. Here we investigate the genus Takifugu that
has undergone explosive radiation relatively recently and contains a
subset of closely-related species with a scale-loss phenotype. By using
observations during development and genetic mapping approaches, we show
that the scale-loss phenotype of
two Takifugu species, T.
pardalis Temminck & Schlegel and T.
snyderi Abe, is largely controlled by an overlapping genomic
segment (QTL). A search for candidate genes underlying the scale-loss
phenotype revealed that the QTL region contains no known genes responsible
for the evolution of scale-loss phenotype in other fishes. These results
suggest that the genes used for the scale-loss phenotypes in the
two Takifugu are likely the same, but the genes used for
the similar phenotype in Takifugu and distantly related
fishes are not the same. Meanwhile, Fgfrl1, a gene predicted to
function in a pathway known to regulate bone/scale development was
identified in the QTL region. Since Fgfr1a1, another memebr of
the Fgf signaling pathway, has been implicated in scale loss/scale shape
in fish distantly related to Takifugu, our results suggest that
the convergence of the scale-loss phenotype may be constrained by
signaling modules with conserved roles in scale development.