Meeting Abstract
Aquatic insects play critical roles in freshwater ecosystems and temperature is a fundamental driver of species performance and distributions. Life history data of mayfly Neocloeon triangulifer show that this species generally follow the temperature size rule, resulting in shorter development time, smaller body size and less fecundity at higher temperatures. However, the physiological mechanisms underlying these thermal effects remain unclear. Published research suggests thermal limits are driven by the mismatch between oxygen supply and demand in the tissues of ectotherms. We tested this hypothesis by rearing the mayfly Neocloeon triangulifer from newly hatched eggs to adulthood at 2 °C intervals ranging from 14 °C to 28 °C. Larvae reared at 30 °C failed to reach adulthood. We then attempt to link physiological processes to life history outcomes by studying gene expression and metabolomics in mature larvae reared at different temperatures. Quantitative PCR results show that hypoxia responsive gene EGG LAYING DEFECTIVE 9 did not respond to long term thermal challenge, whereas genes that were thermally responsive (HEAT SHOCK PROTEIN 90, 40) or involved in the insulin signaling pathway (INSULN RECEPTOR, TARGET OF RAPAMYCIN 1) were significantly increased. Metabolomics data showed that some amino acids and acylcarnitine were negatively associated with temperature. Together, these data suggest that the thermally driven life history outcomes are more likely due to energetic challenges and maintenance costs rather than oxygen limitation.
