Physiological Consequences of Severe Exercise in the Inactive Benthic Flathead Sole (Hippoglossoides Elassodon): a Comparison With the Active Pelagic Rainbow Trout (Salmo Gairdneri)

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Abstract
Chronically cannulated flathead sole were subjected to 10 min of either moderate or exhausting burst exercise and monitored over a 12 h recovery period. Acid-base disturbances were more severe after exhausting exercise, but ionic and haematological changes were the same in the two treatments. Most effects were qualitatively similar to those previously described in severely exercised rainbow trout (Turner, Wood & Clark, 1983). Specific differences are discussed and related to the different external environments sea water vs fresh water), exercise capabilities and ecologies of the two species. The most striking divergence occurred in lactate (La−) and metabolic proton dynamics. Post-exercise La− levels in white muscle in sole were less than half those in trout but declined much more slowly. In contrast to the situation in trout, muscle [La−] remained significantly elevated and large muscle to blood La− gradient persisted even after 12 h recovery. Blood [La−] underwent only minimal elevation (−1), and blood metabolic proton load (ΔH+m) greatly exceeded Δ;La− throughout the recovery period, effects directly opposite those in trout. This observed excess of ΔH+m over ΔLa− in the blood of exercised sole is probably not due to a preferential removal mechanism, because ΔH+m and ΔLa− disappeared from the blood at similar rates after an intra-arterial infusion of lactic acid in resting animals. It is therefore argued that the phenomenon reflects a differential release of the two metabolites from the white muscle of the sole, La− being strictly retained in the muscle for gluconeogenesis in situ.