Intraspecific variation in the thermal plasticity of mitochondria in killifish

Abstract

SUMMARY Populations of the Atlantic killifish (Fundulus heteroclitus) inhabit salt marshes and estuaries along the eastern coast of NorthAmerica from Newfoundland to northern Florida, and are thus exposed to a large range of temperatures. Previous studies have shown higher whole-organism metabolic rates in the northern subspecies (F. h. macrolepidotus) compared with the southern subspecies (F. h. heteroclitus) of these fish. Here, we examine phenotypic plasticity in the response to cold temperatures between the two subspecies by acclimating fish to 5, 15 and 25°C and comparing several mitochondrial and muscle properties. The relative area of oxidative muscle versus glycolytic muscle fibers was greater in the northern subspecies at the 5 and 15°C acclimation temperatures. However, there were no differences in capillary density between the two subspecies or at different temperatures. Mitochondrial volume and surface densities increased in response to cold temperature acclimation in red and white muscle, but only in the northern killifish. Citrate synthase activities also increased in the northern killifish at 5 and 15°C. The ratio of calculated [free ADP] to [ATP] increased in the 5°C acclimated southern killifish but not in the northern killifish at 5°C when compared with the 15°C acclimation group, suggesting that there are differences in adenylate signaling for mitochondrial respiration between subspecies at low temperature. Taken together, our data indicate that the northern subspecies have a greater ability to increase mitochondrial capacity at colder temperatures compared with the southern subspecies, providing one of the few examples of intraspecific variation in phenotypic plasticity in mitochondrial amount in response to cold temperatures.

Dynamic changes in cardiac mitochondrial metabolism during warm acclimation in rainbow trout

“…This could indicate that dysfunctional mitochondria had been eliminated from the cell after day 2. In fish, mitochondrial volume density varies with water temperature and thermal acclimation can induce changes in the cristae surface density of mitochondria as well as mitochondrial volume density (Dhillon and Schulte, 2011;Guderley, 2004;Guderley and Johnston, 1996;Guderley et al, 1997;St-Pierre et al, 1998;Tyler and Sidell, 1984;White et al, 2012) but how and when such changes occur during the acclimation process is unknown. Two different mechanisms are believed to be used by the cell to ensure mitochondrial homeostasis and survival; apoptosis and mitophagy but, to the best of our knowledge, none of these has been considered in the context of thermal acclimation.…”

Steep, coincident, and concordant clines in mitochondrial and nuclear‐encoded genes in a hybrid zone between subspecies of Atlantic killifish,Fundulus heteroclitus

“…2009; Dhillon and Schulte 2011; Baris et al. 2016), suggesting the possibility of functional mismatches in hybrid individuals.…”

Thermal acclimation and subspecies-specific effects on heart and brain mitochondrial performance in a eurythermal teleost (Fundulus heteroclitus)

“…However, acclimation to 5°C is associated with an increase in mitochondrial volume density in F. heteroclitus white muscle (Dhillon and Schulte, 2011). We estimated mitochondrial quantity by measuring heart and brain CS activity (Fig.…”

“…Low-temperature acclimation is associated with increased mitochondrial oxidative phosphorylation (OXPHOS) capacity, mitochondrial volume density and alterations in mitochondrial membrane composition (Chung and Schulte, 2015;Egginton and Johnston, 1984;Grim et al, 2010;Fangue et al, 2009;Kraffe et al, 2007;Dhillon and Schulte, 2011;Schnell and Seebacher, 2008). In contrast, hightemperature acclimation has been associated with changes in mitochondrial membrane fatty acid saturation and lowered mitochondrial respiratory capacity (Chung and Schulte, 2015;Guderley and Johnston, 1996;Khan et al, 2014;Strobel et al, 2013;Baris et al, 2016a;Fangue et al, 2009).…”