Physiological responses of the abalone Haliotis discus hannai to daily and seasonal temperature variations

Abstract

Organisms inhabiting tidal mixing-front zones in shallow temperate seas are subjected to large semidiurnal temperature fluctuations in summer. The ability to optimize energy acquisition to this episodic thermal oscillation may determine the survival, growth and development of these ectotherms. We compared the physiological and molecular responses of Haliotis discus hannai cultivated in suspended cages to fluctuating or stable temperature conditions. Several physiological indicators (respiration, excretion rates and O:N) were measured in both conditions, and alterations in the proteome during thermal fluctuations were assessed. No summer mortality was observed in abalone cultivated in fluctuating temperatures compared with that at stable high temperatures. Metabolic rates increased sharply during stable warm summer conditions and fluctuated in accordance with short-term temperature fluctuations (20–26 °C). Ammonia excretion rates during acute responses were comparable in both conditions. When abalone were exposed to fluctuating temperatures, enzyme activities were downregulated and structure-related protein expression was upregulated compared with that at an acclimation temperature (26 °C), highlighting that exposure to low temperatures during fluctuations alters molecular processes. Our results reveal that modulation of physiological traits and protein expression during semidiurnal thermal fluctuations may buffer abalone from the lethal consequences of extreme temperatures in summer.

Change of Foraging and Hiding Behaviors in the Pacific Abalone Haliotis discus hannai in Response to Elevated Seawater Temperature

“…According to our results, ocean warming may lead to changes in the mean level of foraging and hiding behaviors of abalones. We expected both more active foraging and hiding behaviors of abalones as the temperature of the seawater increases within their optimal temperature ranges because of the increase in their metabolism induced by the temperature increase (Kang et al 2019). However, both more active foraging and hiding behaviors was observed in abalones exposed to a single stimulus (i.e., light or food), indicating that the increasing temperature may not affect the activity of abalones in the same way when they are faced with circumstances in which they must decide whether to feed or hide.…”

Expression of Heat Shock Proteins in Thermally Challenged Pacific Abalone Haliotis discus hannai

“…Its growth and development are influenced by various environmental factors, such as temperature, oxygen, CO 2 , and salinity. Among these, temperature is the most important factor, having a higher correlative effect with other stressors as well as increased summer mortality rates in abalones and other ectothermic slow-crawling shellfishes [1]. For example, increases in atmospheric temperature are reflected in the decreased oxygen solubility in coastal waters, which creates hypoxic conditions for various aerobic underwater organisms, thus causing them to experience internal energy imbalances [2].…”

“…These scenarios are more common in coastal-based marine aquaculture systems because temperature and oxygen cannot be controlled manually, as the systems are subject to environmental conditions. In abalone physiology, in contrast to chronic thermal stress, short-term thermal stress does not influence energy metabolism [1,5,6]. In most cases, when abalone are subjected to higher temperatures for a prolonged period, their energy metabolic state shifts from aerobic to anaerobic, which also affects growth and causes weight loss due to overutilization of energy and reduction of food intake [3].…”

“…Since the 1970s, aquaculture systems for abalone have been continuously promoted in South Korea to maintain sustainable production and meet the global market demand. South Korea has since held fourth place in overall seafood production and was the second largest producer of farmed abalone in the world in 2014 [1,11]. However, a current problem in coastal-based aquaculture is summer mortality, which leads to the highest production loss among farmers [1].…”

“…South Korea has since held fourth place in overall seafood production and was the second largest producer of farmed abalone in the world in 2014 [1,11]. However, a current problem in coastal-based aquaculture is summer mortality, which leads to the highest production loss among farmers [1]. To mitigate temperature-related problems, in-depth knowledge of abalone genetics is required.…”