Rapid metabolic recovery following vigorous exercise in burrow-dwelling larval sea lampreys (Petromyzon marinus)

Although the majority of the sea lamprey's (Petromyzon marinus) life cycle is spent as a burrow-dwelling larva, or ammocoete, surprisingly little is k nown about intermediary metabolism in this stage of the lamprey's life hist ory. In this study, larval sea lampreys (ammocoetes) were vigorously exerci sed for 5 min, and their patterns of metabolic fuel depletion and replenish ment and oxygen consumption, along with measurements of net whole-body acid and ion movements, were followed during a 4-24-h postexercise recovery per iod. Exercise led to initial five- to sixfold increases in postexercise oxy gen consumption, which remained significantly elevated by 1.5-2.0 times for the next 3 h. Exercise also led to initial 55% drops in whole-body phospho creatine, which was restored by 0.5 h, but no significant changes in whole- body adenosine triphosphate were observed. Whole-body glycogen concentratio ns dropped by 70% immediately following exercise and were accompanied by a simultaneous ninefold increase in lactate. Glycogen and lactate were quickl y restored to resting levels after 0.5 and 2.0 h, respectively. The presenc e of an associated metabolic acidosis was supported by very high rates of m etabolic acid excretion, which approached 1,000 nmol g(-1) during the first 2 h of postexercise recovery. Exercise-induced ion imbalances were also ra pidly alleviated, as initially high rates of net Na+ and Cl- loss (-1,200 n mol g(-1) h(-1) and -1,800 nmol g(-1) h(-1), respectively) were corrected w ithin 1-2 h. Although larval sea lampreys spend most of their time burrowed , they are adept at performing and recovering from vigorous anaerobic exerc ise. Such attributes could be important when these animals are vigorously s wimming or burrowing as they evade predators or forage.