Functional significance of metabolic responses to thermal acclimation in fish muscle

Abstract

Compensatory increases of the aerobic capacity of fish swimming muscle are frequently observed in response to cold acclimation. Such thermal compensation occurs both in fish that remain active in the cold and in fish that become dormant at cold temperatures. For cold-active fish, positive thermal compensation is best explained by conservation of the capacity for aerobic metabolic flux at low temperatures. The compensatory responses of cold-active species can be used to suggest the temperature range over which the activities of glycolytic and tricarboxylic acid cycle enzymes in a muscle, i.e., the muscle's "metabolic profile," can suffice. Analysis of the available data suggests that a 16 degrees C range of temperatures cannot be covered by one metabolic profile, even when the preferred temperatures are centered between the acclimation temperatures. For cold-inactive species that remain normoxic during winter dormancy, the compensatory metabolic modifications may facilitate lipid catabolism. Alternately, an increased aerobic capacity may be adaptive during the relatively cold periods that precede and follow winter dormancy. For goldfish and carp that encounter hypoxia and anoxia during winter dormancy, increased mitochondrial abundance could facilitate ethanol production during anoxia and the diffusion of oxygen to mitochondria during hypoxia. Finally, metabolic modifications during natural acclimatization indicate both thermal compensation and direct thermal effects and suggest that thermal compensation may be masked by reproductive and feeding activities.

Oxygen limited thermal tolerance in fish?

“…As outlined above, a rise in aerobic capacity permits maintenance of cell functions in the cold (for review Guderley, 1998;Pörtner et al, , 2001. Associated processes are rising enzyme capacities (Crockett and Sidell, 1990;Guderley, 1990;Lannig et al, 2003), increased mitochondrial or capillary densities (Sisson and Sidell, 1987;Guderley and Blier, 1988;Ressel, 2001), changes in mitochondrial structure (Gaebel and Roots, 1989;St.-Pierre et al, 1998) and/or alterations in membrane composition (Miranda and Hazel, 1996;Logue et al, 2000). Mitochondrial densities are found esp.…”

Origins of variation in muscle cytochrome c oxidase activity within and between fish species

“…Fish respond in a similar manner to activity (e.g. Farrell et al, 1991), but they also induce mitochondrial proliferation in response to cold acclimation and winter acclimatization (Egginton and Sidell, 1989;Egginton et al, 2000;Guderley, 1990). Unlike the situation in mammals, where cold exposure induces hypermetabolism, cold treatment of fish depresses metabolism, leading to a suite of morphological, physiological, biochemical and genetic modifications (Egginton and Johnston, 1984;Johnston and Maitland, 1980;Johnston and Wokoma, 1986;Orczewska et al, 2010;Shaklee et al, 1977).…”

Seasonal acclimatisation of muscle metabolic enzymes in a reptile(Alligator mississippiensis)

“…Acclimatisation is thought to occur particularly in response to long-term changes in environmental conditions, such as to seasonal or latitudinal variation (Scheiner, 1993;Wilson and Franklin, 2000). For example, many fish respond to seasonally changing water temperatures and, hence, body temperatures, by reversibly acclimatising the capacities of their enzyme-catalysed metabolic processes (Guderley, 1990;Segal and Crawford, 1994;Martinez et al, 1999). In addition, there may be differences in metabolic enzyme activities among closely related species living at different latitudes (Pierce and Crawford, 1997).…”