Exercise in the Cold: High Energy Turnover in Antarctic Fish
233
A fast recovery from exhaustive swimming requires largely increased
postexercise metabolic rates to payoff the oxygen debt. Based on
metabolite data we calculated the ATP turnover necessary for
gluconeogenesis, rephosphorylation of PCr and ATP synthesis during the
first hour of recovery and compared the results with data on trout (Fig. 1).
This comparison reveals that the A TP requirement during the first hour of
recovery is about the same in trout at 15°C and Antarctic eelpout at 0 °C!
On the basis of the low resting metabolic rate in the latter (0.38 )lmol O 2
g-l h- 1 compared to 6.3 j.lmol O 2 g-l h- 1 in trout; I. Hardewig, P. van Dijk
and H.O. Portner, unpublished results; [50]) the factorial increase of ATP
production required for recovery is much higher in eelpout. These data
strongly suggest that Antarctic fish show metabolic cold adaptation. This
adaption is not reflected in elevated resting metabolic rates, but becomes
evident during situations of high energy turnover.
Conclusions
Antarctic fish have obviously developed mechanisms to compensate for
the adverse effects of low temperatures on locomotory performance.
Aerobic metabolic capacity and, accordingly, aerobic swimming
velocities exhibit clear cold adaptation in Antarctic species. However, the
increase of aerobic capacity may cause a high sensitivity towards
temperature increases. This may be tolerated in cold stenothermal
Antarctic species that do not experience large temperature variations in
their habitat. Eurythermal organisms, however, must be able to maintain
vital functions over a broad temperature range. A trade off between an
increase in metabolic capacity and tolerance towards shifts in habitat
temperature may have led to different degrees of cold compensation in
stenothermal versus eurythermal species: While both groups generally
appear to employ the same qualitative mechanisms to survive in the cold,
the degree of cold compensation with respect to maximum rates of energy
turnover during exercise and recovery seems to be more pronounced in
stenothermal Antarctic fishes.
References
1. Somero GN, DeVries AL (1967) Temperature tolerance in some Antarctic
fishes. Science 156:257-258
2. Beamish FWH (1978) Swimming capacity. In: Hoar WS, Randall DJ (eds)
Fish physiology. Academic Press, New York, pp 101-187
233
A fast recovery from exhaustive swimming requires largely increased
postexercise metabolic rates to payoff the oxygen debt. Based on
metabolite data we calculated the ATP turnover necessary for
gluconeogenesis, rephosphorylation of PCr and ATP synthesis during the
first hour of recovery and compared the results with data on trout (Fig. 1).
This comparison reveals that the A TP requirement during the first hour of
recovery is about the same in trout at 15°C and Antarctic eelpout at 0 °C!
On the basis of the low resting metabolic rate in the latter (0.38 )lmol O 2
g-l h- 1 compared to 6.3 j.lmol O 2 g-l h- 1 in trout; I. Hardewig, P. van Dijk
and H.O. Portner, unpublished results; [50]) the factorial increase of ATP
production required for recovery is much higher in eelpout. These data
strongly suggest that Antarctic fish show metabolic cold adaptation. This
adaption is not reflected in elevated resting metabolic rates, but becomes
evident during situations of high energy turnover.
Conclusions
Antarctic fish have obviously developed mechanisms to compensate for
the adverse effects of low temperatures on locomotory performance.
Aerobic metabolic capacity and, accordingly, aerobic swimming
velocities exhibit clear cold adaptation in Antarctic species. However, the
increase of aerobic capacity may cause a high sensitivity towards
temperature increases. This may be tolerated in cold stenothermal
Antarctic species that do not experience large temperature variations in
their habitat. Eurythermal organisms, however, must be able to maintain
vital functions over a broad temperature range. A trade off between an
increase in metabolic capacity and tolerance towards shifts in habitat
temperature may have led to different degrees of cold compensation in
stenothermal versus eurythermal species: While both groups generally
appear to employ the same qualitative mechanisms to survive in the cold,
the degree of cold compensation with respect to maximum rates of energy
turnover during exercise and recovery seems to be more pronounced in
stenothermal Antarctic fishes.
References
1. Somero GN, DeVries AL (1967) Temperature tolerance in some Antarctic
fishes. Science 156:257-258
2. Beamish FWH (1978) Swimming capacity. In: Hoar WS, Randall DJ (eds)
Fish physiology. Academic Press, New York, pp 101-187