American locust (Schistocerca americana) post-exercise lactate fate dataset

The fate of lactate after exercise varies between animal groups. In ectothermic vertebrates, lactate is primarily converted to glycogen in the muscle. In mammals, lactate is intramuscularly oxidized or converted to glycogen in the muscle and/or liver. In addition, the rate at which post-exercise lactate pools are depleted varies between taxa. Grasshoppers are unique among insects in that they produce lactic acid during locomotion. However, it is unclear where the lactate is processed. Furthermore, insects have extremely efficient oxygen delivery systems which may enhance lactate removal compared to an ectothermic vertebrate. We fluorometrically measured lactate levels in the American locust (Schistocerca americana) during recovery from jumping. Male grasshoppers were forced to jump for five minutes in a large gloved box at 35 °C. After jumping, individuals were either immediately sampled for lactate or allowed to recover in insolation at 35 °C for different time periods (15, 30, or 60 min) before being processed for lactate. Lactate was measured in the hemolymph, jumping muscle, and abdomen of each grasshopper. A control group was isolated overnight but not jumped to provide pre-jumping lactate levels. During recovery, hemolymph and abdominal lactate levels remain virtually the same whereas muscle lactate levels decrease, suggesting that grasshoppers process lactate intramuscularly. Compared to mammals, ectothermic vertebrates have higher intramuscular lactate and lower blood lactate values after exhaustive activity [reviewed in 1]. Furthermore, small mammals process and remove most blood lactate in approximately 20 min, while ectothermic vertebrates require multiple hours to recover [1]. Since grasshoppers have significantly more lactate in their muscle than hemolymph and their hemolymph lactates remain elevated at least one hour after recovery, grasshopper post-exercise lactate metabolism is more similar to ectothermic vertebrates than mammals.