Respiratory plasticity in the amphibious fish, Kryptolebias marmoratus during emersion
Amphibious fishes have evolved multiple adaptive strategies for respiring out of water. I tested the hypothesis that in amphibious fish that leave water, enhanced respiratory performance on land is the result of rapid functional phenotypic flexibility of respiratory traits. Initially, K. marmoratus had improved respiratory performance (lower aerial critical oxygen tension (Pcrit), higher regulation index (RI)) after only 1 day of air exposure. Initial changes in aerial Pcrit were strongly associated with the relative change in hematocrit. Also, initial changes in RI were highly linked to increased dorsal cutaneous angiogenesis. Long-term changes (7 days) in respiratory traits were not significantly linked to the variation in either aerial Pcrit and RI. Overall, two phases were involved in the enhancement of aerial respiration; an initial rapid response and a delayed response. My findings suggest that the initial rapid response is due to flexibility in both O2-uptake and O2-carrying capacity.