Meeting Abstract
Calanus finmarchicus is a highly abundant copepod that acts as an important primary consumer in North Atlantic ecosystems. In this species, the last juvenile stage (fifth copepodid, C5) is of particular interest because individuals may either delay maturation and enter a dormant period or molt directly into adults. We seek to understand the physiological changes associated with progression of the copepods along each of these two paths, and in this study, we characterize the direct path toward the terminal molt. We sampled lab-reared C. finmarchicus copepods daily throughout the C5 stage and assessed molt stage progression, gonad development and lipid storage. We conducted Illumina-based RNA-seq to identify a large pool of differentially expressed genes during early and late stages of the C5 molt cycle. We monitored the population daily throughout the C5 stage to assess molt stage progression, gonad development, lipid storage and expression of specific genes. We found that copepods varied considerably in molt stage duration and that progression through the stage was associated with substantial accumulation of lipids within the oil sac. Among the genes exhibiting dynamic expression profiles, many were associated with energetic storage and metabolism. In particular, genes comprising the pentose phosphate and glycolysis pathways, as well as genes necessary for triglyceride and wax ester storage were usually upregulated early in the molt cycle. These gene expression profiles are consistent with widespread metabolic changes coupled with accumulation of lipids and progression through the molt cycle.
