Meeting Abstract

90.4  Monday, Jan. 6 14:15  Does temperature affect aquatic insects via oxygen limitation? BUCHWALTER, D*; CAMP, A; KIM, K; FUNK, D; PATHMASIRI, W; RAYMER, J; SUMNER, S; North Carolina State University; North Carolina State University; North Carolina State University; Stroud Water Research Center; Research Triangle Institute ; Research Triangle Institute ; Research Triangle Institute david_buchwalter@ncsu.edu

Oxygen limitation has been proposed as the fundamental mechanism responsible for establishing thermal limits in ectotherms. This paradigm is based on data from several species that indicate that the metabolic demands associated with thermal challenge are not met with commensurate uptake and delivery of oxygen to tissues. To test whether this paradigm can be applied to aquatic insects, we combined respirometry, gene expression (qPCR) and metabolic profiling studies in an emerging mayfly laboratory model – Centroptilum triangulifer (Ephemeroptera: Baetidae). Thermal ramping studies were conducted at an environmentally relevant ramping rate of 1°C/hour from a base culture temperature of 22 °C to 34°C. Intermittent-flow respirometry studies revealed the expected logarithmic increase in oxygen consumption with no evidence of leveling off or plateauing a higher temperatures. qPCR studies in larvae sampled at 4°C intervals showed strong thermal responses in heat shock protein genes, with no evidence of genes associated with hypoxia inducible factor (HIF) signaling. At 34°C (beyond the thermal tolerance of this species in life cycle rearing tests), we observed a very modest increase in lactate dehydrogenase (LDH) gene expression relative to its expression levels in hypoxia-treated positive controls, suggesting that obviously heat stressed C. triangulifer were not experiencing oxygen limitation. Metabolic profiling studies indicate that purine metabolism, urea cycle, and fatty acid metabolism are affected by thermal challenge.