41.4 Thursday, Jan. 5 Terrestrially induced gill remodelling reduces the aquatic respiratory function of Kryptolebias marmoratus TURKO, A*; COOPER, C; WRIGHT, P; University of Guelph; University of Guelph; University of Guelph email@example.com
Amphibious fish use a suite of reversible plastic changes to their behaviour, physiology, and morphology when switching between aquatic and terrestrial habitats. Some of these responses occur rapidly (i.e. behaviour), while others occur over days or weeks (i.e. morphology). The mangrove rivulus, Kryptolebias marmoratus, may spend weeks in terrestrial habitats. During these periods the gills are remodelled, reducing surface area. I tested the hypothesis that this remodelling would negatively impact respiratory function upon returning to aquatic breathing. I predicted that air-acclimated fish would show a hypoxic ventilatory response at a higher level of dissolved oxygen, and have a higher critical oxygen tension (Pcrit), than brackish water controls. Custom-built chambers were used to non-invasively measure gill ventilation as fish were exposed to stepwise decreases in dissolved oxygen. Closed respirometry was used to measure metabolic rate and Pcrit. Fish with reduced gill surface area increased ventilatory activity at a significantly higher oxygen concentration than control fish, and took longer to recover from hypoxic exposure. Pcrit was unaffected by gill morphology. The increased sensitivity to hypoxia in air-exposed fish indicates that reversible gill remodelling has consequences for respiratory function upon switching respiratory media. Increased gill ventilation was able to compensate for gills with reduced surface area during acute hypoxic exposure, as Pcrit did not differ between groups. However, the increased recovery time of air-exposed fish suggests that increased gill ventilation may not suffice over longer time scales. Overall, these results demonstrate how behavioural and morphological plasticity are temporally integrated in mangrove rivulus during the transition between aquatic and terrestrial habitats.