Response of cold-acclimated, farmed South African abalone (Haliotis midae) to short-term and long-term changes in temperature

In its natural environment, the South African abalone, Haliotis midae, occurs at average monthly water temperatures between 12 and 21 °C. In the present study we aimed to describe selected physiological and molecular responses of winter acclimated, cultured H. midae after acute and chronic exposure to 16, 19 and 22 °C.During acute (24 h) exposure to 16, 19 and 22 °C we found a significant increase in specific rates of oxygen consumption and nitrogen excretion with higher temperature. This corresponded with a higher reliance on proteins to fuel metabolism and coincided with high d-lactate levels at the 16 °C and high levels of Hsp70 proteins at all three temperatures.After chronic (1 month) exposure to 16, 19 and 22 °C animals compensated for changes in temperature by decreasing their specific oxygen consumption and nitrogen excretion rates with increase in temperature, showing that the animals had a high level of reliance on carbohydrates as food source at 22 °C. d-lactate levels were lower than after acute exposure and Hsp70 protein levels were lower at 16 and 19 °C, but remained high at 22 °C. Total muscle protein levels were lower in 16 and 19 °C animals and very high at 22 °C, indicating that animals incorporate proteins into their tissue, because they do not rely on protein catabolism to the same extent compared to lower temperatures.We conclude that cold acclimated H. midae have the ability to adapt to high temperatures, within their optimal range for growth, provided that they are exposed to sustained stable temperatures and do not experience short, high temperature spikes. These findings will aid in a better understanding of feed utilization and growth patterns of H. midae in the thermally variable intensive mariculture environment.