Oxidative stress in abalone: The role of temperature, oxygen and L-proline supplementation

In their natural distribution range and in on land-based mariculture facilities, Haliotis midae may be exposed to a relatively wide range of temperatures and oxygen levels, that can induce differential degrees of stress with concomitant metabolic responses. In the current study juvenile H. midae were exposed for one month to two constant temperatures (14 degrees C and 19 degrees C), with three oxygen levels (82%, 98% and 126% oxygen saturation) at each temperature. One additional treatment was included at 19 degrees C, 126% oxygen, where feed was supplemented with L-proline. The results presented here suggest that long-term 19 degrees C exposure is more stressful to H. midae juveniles than a 14 degrees C exposure of the same duration, since exposure to higher temperature generally resulted in higher activities of the antioxidant enzymes measured but lower total antioxidant capacities. Haemolymph glucose levels responded to oxygen treatment at the 14 degrees C exposure, but the same response was not initiated in the 19 degrees C treatment, possibly because the animals exposed to the 19 degrees C treatment relied on proteins to a larger extent. Increased oxygen levels at the 19 degrees C treatment did not cause more DNA damage or protein carbonylation compared to lower oxygen levels. Supplementing feed with L-proline at the high temperature/high oxygen treatment caused a decrease in haemolymph haemocyanin (which may exhibit catalase function) content and a slight decrease in some of the antioxidant enzyme activities, while maintaining the same total antioxidant capacity compared with the same treatment where feed was not supplemented. The overall DNA integrity profile also changed with proline-supplementation, as did the induction level of hsp70. When projecting tissue growth over a 12 month period under these conditions, we estimate that H. midae juveniles in this study may exhibit a significant increase in mass when their feed was supplemented with L-proline, indicating that L-proline supplementation provides some benefit to the individual. It might therefore warrant conducting long-term growth trials on land-based mariculture facilities to further investigate its potential benefit to the mariculture industry. (C) 2013 Elsevier B.V. All rights reserved.