Exercise–related muscle lactate metabolism in zebrafish juveniles: The effect of early life temperature

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The accumulation of lactate in fish muscles during exercise and particularly its decomposition rate afterwards is a process of great importance, as it significantly influences swimming capacity. In the present study, zebrafish juveniles were reared at different water temperatures (22°C, 25°C, 28°C and 31°C) and before being subjected to the swimming trials (according to Brett's method) they were acclimated to a common intermediate temperature of 26.5°C for 45 days. Muscle lactate concentration was estimated on 35 specimens per temperature origin, which were sampled at the following time periods: at rest, after full exhaustion due to swimming and after recovery for thirty minutes, one hour, three hours, six hours and nine hours. Lactate analysis revealed that in all cases, lactate metabolism follows that previously described for other species patterns, since its concentration rises during exercise and decreases during the recovery time. It was also shown that developmental temperature affects not only the initial and final lactate concentration (at rest and at full exhaustion respectively), but its decomposition rate during recovery as well since the 22°C-reared fish require considerably more time than the others in order to fully recover and the 31°C-reared fish present the fastest recovery among all. Developmental temperature during the early life stages is once again proven to play an important role in the subsequent life of the fish.