Calanus finmarchicus diapause

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Did you ever wonder, attentive reader, why our model results only span the late winter / spring season? Well, first most of the modeling effort developed in the EML aims at a better understanding of the timing of arrival of right whales in the Gulf of Maine area, and this occurs around spring. Second, our beloved copepod Calanus finmarchicus (the most delicious meal for the right whales!) disappears for most of the year from the surface waters. They escape and survive unfavorable environmental conditions (which is between fall and winter, everybody in New England will acknowledge that...) by staying at depth in a dormancy (diapause) state right before their final molt into adults. Dormancy means that every function of the organism is slowed down, no feeding takes place, and the only active behavior is, perhaps, a sluggish swimming to remain at depth.

Maybe you will be skeptical while you read me stating that little is known yet about the triggers controlling the entrance into and the exit from dormancy in C. finmarchicus. But... well, so it is !  Hence, as this species spends routinely more than half its life cycle down there, the EML has to broaden its interests to include the dormancy issue. And a promising approach to better understand dormancy makes use of the lipids stored in the so called "oil sac" of the copepods. The rationale is that lipids are a very efficient way of storing energy. Remember that while C. finmarchicus does not feed during dormancy, it spends most of its life cycle in that state. Thus, dormant individuals need huge amounts of energy reserves, which are in the form of lipids. Entrance into dormancy must be linked with the amount of lipid storage an individual managed to build up during its development. Indeed, you can see on this picture of a copepodid 5 of C. finmarchicus (the stage during which dormancy takes place) the impressive body volume occupied by the oil sac. When the diapause period approaches its end however, most of the lipid storage is used. Nevertheless, a certain amount of lipid still need to remain, in order to produce the gonadic tissue and the final molt. Exit from dormancy must be linked to the minimal amount of lipid required by these different steps of the final maturation.

Following these observations and deductions, the EML is now resolved to tackle the diapause issue. So be prepared to see soon model results during winter time !

Photo by Phoebe Jekielek.

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This page contains a single entry by Frederic Maps published on August 20, 2009 10:35 PM.

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