Variations in copepod proteome and respiration rate in association with diel vertical migration and circadian cycle

Author Posting. © University of Chicago, 2018. This article is posted here by permission of University of Chicago for personal use, not for redistribution. The definitive version was published in Biological Bulletin 235 (2018): 30-42, doi:10.1086/699219.The diel vertical migration of zooplankton is a process during which individuals spend the night in surface waters and retreat to depth during the daytime, with substantial implications for carbon transport and the ecology of midwater ecosystems. The physiological consequences of this daily pattern have, however, been poorly studied beyond investigations of speed and the energetic cost of swimming. Many other processes are likely influenced, such as fuel use, energetic trade-offs, underlying diel (circadian) rhythms, and antioxidant responses. Using a new reference transcriptome, proteomic analyses were applied to compare the physiological state of a migratory copepod, Pleuromamma xiphias, immediately after arriving to the surface at night and six hours later. Oxygen consumption was monitored semi-continuously to explore underlying cyclical patterns in metabolic rate under dark-dark conditions. The proteomic analysis suggests a distinct shift in physiology that reflects migratory exertion and changes in metabolism. These proteomic analyses are supported by the respiration experiments, which show an underlying cycle in metabolic rate, with a peak at dawn. This project generates molecular tools (transcriptome and proteome) that will allow for more detailed understanding of the underlying physiological processes that influence and are influenced by diel vertical migration. Further, these studies suggest that P. xiphias is a tractable model for continuing investigations of circadian and diel vertical migration influences on plankton physiology. Previous studies did not account for this cyclic pattern of respiration and may therefore have unrepresented respiratory carbon fluxes from copepods by about 24%.Funding for ET-S was provided by a Training Grant from the National Institutes of Health (T32 HG00035), and proteomics work was supported in part by the University of Washington’s Proteomics Resource (UWPR95794). Funding was provided by Simon’s Foundation International as part of the BIOSSCOPE project.2019-08-1