Skin ionocyte density of amphibious killifishes is shaped by phenotypic plasticity and constitutive interspecific differences

The purpose of this study was to test two hypotheses. The first, that the skin ionocyte density of amphibious fishes is constitutively different from that of exclusively water-breathing species in order to promote ionoregulation via the skin in terrestrial environments. The second, that in amphibious species air-exposure will plastically alter skin ionocyte density to promote ionoregulation via the skin in terrestrial environments. To test these hypotheses we examined the skin of fishes spanning a range of amphibiousness.