Project: Identification of Diagnostic Markers of Diapause Preparation in the Copepod Calanus finmarchicus

Extracted from the NSF award abstract:

Oceanic copepods in the family Calanidae, such as Calanus finmarchicus, are among the most abundant animals on the planet, and they serve a key role in marine food webs by transferring energy from phytoplankton to higher trophic levels. The life history of these copepods has been well-studied, but fundamental questions remain about the regulation of an important period of dormancy called diapause. In the last juvenile stage of development, C. finmarchicus either proceed to the terminal molt (i.e., molt into adults) or vertically migrate to depth and initiate diapause. This divergence in developmental pathways has critical implications for C. finmarchicus population dynamics, but is difficult to study experimentally because C. finmarchicus, like all other copepods in the family Calanidae, do not reliably enter diapause in the laboratory. In addition, most temperate populations of calanoid copepods have multiple generations in a single year with variability in the timing of reproduction and development that causes significant heterogeneity in age structure. Thus, field sampling of these heterogeneous populations yields a mixture of copepods that are preparing for diapause, are preparing for the terminal molt, or are not yet preparing for either fate. Studies of diapause preparation in such populations are extremely difficult.

To enable direct investigation of the factors that influence diapause initiation, we require markers that reliably predict the fate of individual copepods (entry into diapause or continued maturation to adulthood) within heterogeneous populations. Fortunately, the fjord population of C. finmarchicus off the coast of Norway during the late spring is remarkably synchronous and is comprised of juvenile copepods that are all destined to undergo diapause. This project will use high-throughput 454 pyrosequencing to identify genes that change in expression as these copepods progress toward diapause. In collaboration with Norwegian researchers, the investigators will also rear copepods in a unique continuous culture and conduct additional transcriptional profiling to identify genes that change in expression as copepods prepare for the terminal molt. Comparison of gene expression patterns in the wild and cultured populations will enable the principal investigators to develop robust markers of diapauses preparation that can be used to study diapause initiation in more heterogeneous temperate populations.