An examination of the metabolic processes underpinning critical swimming in Atlantic cod (Gadus morhua L.) using in vivo 31P-NMR spectroscopy
Traditionally, critical swimming speed has been defined as the speed when a fish can no longer propel itself forward, and is exhausted. To gain a better understanding of the metabolic processes at work during a U crit swim test, and that lead to fatigue, we developed a method using in vivo 31P-NMR s...
Published in: | Journal of Experimental Biology |
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Main Authors: | , , |
Format: | Text |
Language: | English |
Published: |
Company of Biologists
2007
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Subjects: | |
Online Access: | http://jeb.biologists.org/cgi/content/short/210/21/3749 https://doi.org/10.1242/jeb.008763 |
Summary: | Traditionally, critical swimming speed has been defined as the speed when a fish can no longer propel itself forward, and is exhausted. To gain a better understanding of the metabolic processes at work during a U crit swim test, and that lead to fatigue, we developed a method using in vivo 31P-NMR spectroscopy in combination with a Brett-type swim tunnel. Our data showed that a metabolic transition point is reached when the fish change from using steady state aerobic metabolism to non-steady state anaerobic metabolism, as indicated by a significant increase in inorganic phosphate levels from 0.3±0.3 to 9.5±3.4 mol g–1, and a drop in intracellular pH from 7.48±0.03 to 6.81±0.05 in muscle. This coincides with the point when the fish change gait from subcarangiform swimming to kick-and-glide bursts. As the number of kicks increased, so too did the Pi concentration, and the pH i dropped. Both changes were maximal at U crit . A significant drop in Gibbs free energy change of ATP hydrolysis from –55.6±1.4 to –49.8±0.7 kJ mol–1 is argued to have been involved in fatigue. This confirms earlier findings that the traditional definition of U crit , unlike other critical points that are typically marked by a transition from aerobic to anaerobic metabolism, is the point of complete exhaustion of both aerobic and anaerobic resources. |
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