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

• Main Authors: Schiffer, Melanie, Harms, Lars, Lucassen, Magnus, Mark, Felix, Pörtner, Hans-Otto, Storch, Daniela
• Format: Other/Unknown Material
• Language: English
• Published: BioMed Central Ltd. 2014
• Subjects: Hyas araneus; Larvae; Ocean acidification; Climate change; Thermal tolerance; Gene expression
• Online Access: http://www.frontiersinzoology.com/content/11/1/87

Abstract Introduction Exposure to elevated seawater P CO 2 limits 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 CO 2 on 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 P CO 2 . 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 P CO 2 , while the already low heat tolerance of megalopa larvae was not limited further by hypercapnic exposure. There was a combined effect of elevated seawater CO 2 and 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 CO 2 and 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 CO 2 levels. The present study underlines the necessity to align transcriptomic data with physiological responses when addressing mechanisms affected by an interaction of elevated seawater P CO 2 and temperature extremes.