Copepod (Calanus) Diapause Regulation

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Enlarge ImageAmalia Aruda isolates a single copepod on a spoon so she can examine it under the microscope to determine it's developmental stage. We examined thousands of copepods this way during our May/June 2012 studies in Trondheim, Norway! (photo by N. Lysiak)

Enlarge ImageMark Baumgartner prepares a net for a zooplankton tow. (A. Aruda)

Enlarge ImageR/V Gunnerus, the ship we used to sample active and diapausing copepods within Trondheim Fjord in May/June 2012. (photo by N. Lysiak)

Why are we interested in calanoid diapause?

Calanoid copepods are among the most abundant animals on the planet, and they play a critical role in transferring energy from the base of the food chain to higher consumers. Being able to predict spatial and temporal patterns in copepod abundance is necessary for fisheries models.

Some copepods, such as Calanus finmarchicus, can undergo a dormant period (diapause) during their juvenile development. As juvenile copepods develop, they accumulate lipid energy stores. Some of the copepods will then continue to develop to adulthood and become reproductively active. During periods of low food availability, other individual copepods will migrate to deep water, slow their metabolism and remain dormant for several months. When the copepods emerge from diapause, they swim to the surface, develop to adults and mate.

It is not well understood how copepods decide whether to undergo diapause, or when to initiate and terminate diapause.

Our Approach

We have used molecular techniques to identify changes in gene expression associated with diapause (see publications).

This research is complicated by the fact that it is not currently possible to reliably induce diapause in the lab. We feel that the next critical step is to characterize global changes in gene expression as copepods progress through the molt stage. Working with collaborators at SINTEF and NTNU (Norway), we have sampled cultured copepods throughout the C5 stage. We will use high-throughput sequencing, quantitative PCR and morphological analysis to identify diagnostic changes associated with development.

We have also completed fine scale field sampling that will enable us to test for molecular and morphological changes associated with progression toward diapause.

Publications

Tarrant AM, Baumgartner MF, Verslycke T, Johnson CL. 2008. Differential gene expression in diapausing and active Calanus finmarchicus (Copepoda). Marine Ecology Progress Series 355: 193-207.

Aruda AM, Baumgartner MF, Reitzel AM, Tarrant AM. (2011). Heat shock protein expression during stress and diapause in the marine copepod Calanus finmarchicus. Journal of Insect Physiology 57(5):665-75.