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

AbstractWhen amphibious fishes are on land, gill function is reduced or eliminated and the skin is hypothesized to act as a surrogate site of ionoregulation. Skin ionocytes are present in many fishes, particularly those with amphibious life histories. We used nine closely related killifishes spanning a range of amphibiousness to first test the hypothesis that amphibious killifishes have evolved constitutively increased skin ionocyte density to promote ionoregulation on land. We found that skin ionocyte densities were constitutively higher in five of seven amphibious species examined relative to exclusively water-breathing species when fish were prevented from leaving water, strongly supporting our hypothesis. Next, to examine the scope for plasticity, we tested the hypothesis that skin ionocyte density in amphibious fishes would respond plastically to air-exposure to promote ionoregulation in terrestrial environments. We found that air-exposure induced plasticity in skin ionocyte density only in the two species classified as highly amphibious, but not in moderately amphibious species. Specifically, skin ionocyte density significantly increased inAnablepsoides hartii (168%) andKryptolebias marmoratus (37%) following a continuous air-exposure, and only inK. marmoratus (43%) following fluctuating air-exposure. Collectively, our data suggest that highly amphibious killifishes have evolved both increased skin ionocyte density as well as skin that is more responsive to air-exposure...
Source: Journal of Comparative Physiology B: Biochemical, Systemic, and Environmental Physiology - Category: Physiology Source Type: research