Effect of transport in hyperxic conditions on oxidative balance and secondary stress responses in Peckoltia oligospila (Günther, 1864)
The transport of aquatic organisms in a closed system is widely used in aquaculture. The health and survival of the fish for long periods, as well as the maintenance of water quality in good conditions is ensured by the method of injecting pure oxygen into the transport packaging. However, these transports are most often performed empirically, without having information about their physiological implications. In this context, the present study sought to analyze the effect of transport and hyperoxic water on secondary responses to stress (plasma glucose and osmolality), lipid oxidative damage (TBARS) and total antioxidant capacity against peroxyl radicals (ACAP) in the gills, brain, liver and muscle of “acari bola” (Peckoltia oligospila) submitted to different times (3, 6,12 and 24 h) closed system transport under normoxia (7 mg L-1), moderate hyperoxia (HM = 13 mg L-1) and severe hyperoxia (HS = 23 mg L-1). There were no changes in blood glucose and plasma osmolality. At the end of the transport, no mortality was detected in any of the dissolved oxygen concentrations and transport times. The water quality showed less accumulation of ammonia in the HM and HS treatments compared to the water levels of animals transported in normoxia after 24 h. The liver showed a lower ACAP after 6 h under HS, while oscillations were observed in the muscle over 24 h in fish under normoxia, which in theory is attributed to the circadian rhythm as seen in fish and shrimp. In gills after 12 h ACAP in HS decreased in relation to fish in normoxia and HM at the same time,whereas in the brain, ACAP was lower after 3 h of transport under normoxia, increasing again after 6 h, remaining similar in other transport and treatment times. The TBARS content in the liver decreased by 6 under HS compared to fish transported under normoxia, but at 12 h transport in HM determined greater lipid damage compared to the 6 and 24 h transport in HM. In the muscle, the concentration of TBARS was lower after 12 h under HS compared to fish in normoxia at the same time. Finally, no significant changes were observed in the gills and brain. In conclusion, despite the variations observed in ACAP, especially in muscle, the antioxidant competence in the organs seemed to be sufficient to preserve them against oxidative stress,there is no worsening of lipid damage due to the transport time or initial concentration of dissolved oxygen. Since hyperoxia provided less accumulation of ammonia at the end of the longest transport (24 h), it is recommended for this species to use high concentrations of oxygen in the water. New analyzes must be carried out to better elucidate the mechanisms responsible for the low levels of lipoperoxidation in fish submitted to transport in hyperoxia.