Acid-base regulation and physiological responses to aquaculture and global change stressors in euryhaline crustaceans
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Date
2022-08-24
Authors
Quijada-Rodriguez, Alex
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Abstract
Decapod crustaceans regularly face intrinsic and extrinsic stressors that challenge pH homeostasis, which is compensated through the process of acid-base regulation. Prior research on acid-base regulation in crustaceans has focused on stressors commonly experienced during day-to-day life like exercise or that experienced in estuarine environments such as changes in O2, CO2, and salinity. More recent work has centralized on ocean acidification. However, the effects of global change on freshwater crustaceans (chapter 2) and the effects of elevated CO2 in aquaculture (chapter 3) have been largely ignored. In addition, the effects of feeding on acid-base regulation (chapter 4) have gone unstudied and may have direct implications on responses to global change and aquaculture. This thesis addressed this gap in the literature using the Chinese mitten crab Eriocheir sinensis, Whiteleg shrimp Litopenaeus vannamei, and Green crab Carcinus maenas as models. In chapter 2, I identified that freshwater acidification leads to a greater reliance on protein catabolism and an energetic trade-off allowing for compensation of pH homeostasis but impairment of other physiological processes like calcification and locomotory behaviour. In chapter 3, I determined that chronic growth of Whiteleg shrimp in CO2 levels found in aquaculture facilities did not affect growth or survival when reared in brackish water as opposed to what is seen when reared in full-strength seawater. While growth and survival are unimpaired, extracellular acid-base status varies between shrimp grown at low and high CO2, suggesting a potential for chronic impairment of pH homeostasis. In chapter 4, I found that feeding leads to respiratory acidosis, likely driven by increased acid production from postprandial aerobic metabolism. This acid-base disturbance was not compensated through the accumulation of HCO3- as is seen with respiratory acidosis caused by increased environmental CO2. Instead, acidosis was mainly recovered through large increases in ammonia and to a lesser degree titratable acid excretion. Overall, the data in this thesis provides valuable insights into understanding how global change and aquaculture influences the physiology of decapod crustaceans and provides fundamental information on feeding physiology to stimulate future research into the combined effects of feeding during aquaculture acid-base stressors.
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Keywords
Crab, Ocean acidification, Freshwater acidification, ion transport, ammonia excretion, pH balance