Spiny and soft-rayed fin domains in acanthomorph fish are established through a BMP- <i>gremlin</i> - <i>shh</i> signaling network
Rebekka Höch, Ralf Schneider, Alison Kickuth, Axel Meyer, Joost M. Woltering
Abstract
Significance The “spiny fin,” comprising the anterior part of the dorsal and anal fins, is an evolutionary novelty that contributed to the success of the spiny-rayed fishes. This domain contains heavily ossified spines that serve as defense mechanism and differ from the posterior flexible soft rays. We show that the partitioning of the median fins into spines and soft rays is established through canonical developmental mechanisms responsible for the anterior–posterior patterning of appendages. Furthermore, the coloration of the anal fin in males appears to be genetically linked to soft-ray identity. Comparative analysis including nonacanthomorph fins indicates that the convergent evolution of fin spines across fishes likely involved the repeated exaptation of a deeply conserved developmental program from the anterior fin.