001. 2020. Interestingly, in one swordtail species, Xiphophorus hellerii, differential expression of kcnh8 was linked to development of a male decorative trait, a ventral outgrowth of the caudal fin, called sword Schartl et al. 2020. In zebrafish and goldfish long fin mutants, mutations in paralogous potassium channel genes kcnh2a, kcnk5b, and kcc4a, cause overgrowth of various styles of fins Perathoner et al. 2014; Lanni et al.