Effects of hypoxia and reoxygenation on the energetic metabolism of the crab Neohelice granulata (Decapoda, Varunidae)

Many studies have been performed concerning the effects of hypoxia in crustaceans. However, the effects of reoxygenation are not well understood. The aim of this work was to verify the effects of different times of severe hypoxia (0.5 mgO2.L- 1) and reoxygenation on the energetic metabolism in the locomotor muscle of the crab Neohelice granulata. First, the tolerance and resistance to hypoxia and the recovery time under reoxygenation were estimated. Thereafter, the crabs were submitted to 1, 4 and 10 h of severe hypoxia (0.5 mgO2.L- 1), 30 and 120 min of reoxygenation. Animal oxygen consumption (MO2), locomotor activity, hemolymph glucose and lactate, together with glycogen, glucose, ATP content and mitochondrial complex IV activity were analyzed in the locomotor muscle. N. granulata showed a LC50 between 2.0 and 2.5 mgO2.L- 1 and the crab presented a fast recovery after hypoxia exposure. During hypoxia, the locomotor activity did not decrease as intensely as MO2, probably being maintained by the high levels of lactate verified after short and intermediate hypoxia exposure in the locomotor muscle. During reoxygenation, a fast activation in the aerobic metabolism was observed after short and intermediate hypoxia. However, after long exposure to hypoxia, near the resistance time of this specie, problems in the electron transport chain may be occurring. These results suggest demonstrated that N. granulata use the anaerobic metabolism almost whole periods of hypoxia. On reoxygenation the capacity to rapidly activate the aerobic metabolism is dependent on the time of hypoxia exposure.

• The crab Neohelice granulata have tolerance to hypoxia similar to other crabs.
• During hypoxia, the metabolic depression is delayed in this crab.
• The activation of aerobic pathway depends of hypoxia exposure during reoxygenation.