Tipping points of gastric pH regulation and energetics in the sea urchin larva exposed to CO2 -induced seawater acidification

Publication date: August 2019Source: Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 234Author(s): Hae-Gyeong Lee, Meike Stumpp, Jia-Jiun Yan, Yung-Che Tseng, Sebastian Heinzel, Marian Yong-An HuAbstractSea urchin larvae reduce developmental rates accompanied by changes in their energy budget when exposed to acidified conditions. The necessity to maintain highly alkaline conditions in their digestive systems led to the hypothesis that gastric pH homeostasis is a key trait affecting larval energy budgets leading to distinct tipping points for growth and survival.To test this hypothesis, sea urchin (Strongylocentrotus purpuratus) larvae were reared for 10 days in different pH conditions ranging from pH 7.0 to pH 8.2. Survival, development and growth rates were determined demonstrating severe impacts < pH 7.2. To test the effects of pH on midgut alkalization we measured midgut pH and monitored the expression of acid-base transporters. While larvae were able to maintain their midgut pH at 8.9-9.1 up to an acidification level of pH 7.2, midgut pH was decreased in the lower pH treatments. The maintenance of midgut pH under low pH conditions was accompanied by dynamic changes in the expression level of midgut acid-base transporters. Metabolic rates of the larvae increased with decreasing pH and reached a threshold between pH 7.0 and pH 7.3 where metabolic rates decreased again. Methylation analyses on promoter CpG islands ...
Source: Comparative Biochemistry and Physiology Part A: Molecular and Integrative Physiology - Category: Biochemistry Source Type: research