Temperature tolerance of different larval stages of the spider crab Hyas araneus exposed to elevated seawater PCO2

• Published in: Frontiers in zoology 2014-12, Vol.11 (1), p.87-87, Article 87
• Main Authors: Schiffer, Melanie, Harms, Lars, Lucassen, Magnus, Mark, Felix Christopher, Pörtner, Hans-Otto, Storch, Daniela
• Format: Article
• Language: English
• Subjects: adults; bicarbonates; crabs; Decapoda; enzyme activity; gene expression; gene expression regulation; Genes; Genetic aspects; Global temperature changes; Growth; heart rate; heat; heat shock proteins; heat stress; heat tolerance; hypercapnia; larvae; oxidative phosphorylation; oxygen consumption; Physiological aspects; physiological response; rearing; seawater; temperature; transcriptomics
• ISSN: 1742-9994; 1742-9994
• DOI: 10.1186/s12983-014-0087-4

INTRODUCTION: Exposure to elevated seawater PCO₂limits the thermal tolerance of crustaceans but the underlying mechanisms have not been comprehensively explored. Larval stages of crustaceans are even more sensitive to environmental hypercapnia and possess narrower thermal windows than adults. RESULTS: In a mechanistic approach, we analysed the impact of high seawater CO₂on parameters at different levels of biological organization, from the molecular to the whole animal level. At the whole animal level we measured oxygen consumption, heart rate and activity during acute warming in zoea and megalopa larvae of the spider crab Hyas araneus exposed to different levels of seawater PCO₂. Furthermore, the expression of genes responsible for acid–base regulation and mitochondrial energy metabolism, and cellular responses to thermal stress (e.g. the heat shock response) was analysed before and after larvae were heat shocked by rapidly raising the seawater temperature from 10°C rearing temperature to 20°C. Zoea larvae showed a high heat tolerance, which decreased at elevated seawater PCO₂, while the already low heat tolerance of megalopa larvae was not limited further by hypercapnic exposure. There was a combined effect of elevated seawater CO₂and heat shock in zoea larvae causing elevated transcript levels of heat shock proteins. In all three larval stages, hypercapnic exposure elicited an up-regulation of genes involved in oxidative phosphorylation, which was, however, not accompanied by increased energetic demands. CONCLUSION: The combined effect of seawater CO₂and heat shock on the gene expression of heat shock proteins reflects the downward shift in thermal limits seen on the whole animal level and indicates an associated capacity to elicit passive thermal tolerance. The up-regulation of genes involved in oxidative phosphorylation might compensate for enzyme activities being lowered through bicarbonate inhibition and maintain larval standard metabolic rates at high seawater CO₂levels. The present study underlines the necessity to align transcriptomic data with physiological responses when addressing mechanisms affected by an interaction of elevated seawater PCO₂and temperature extremes.