Composition of wax esters is linked to diapause behavior of Calanus finmarchicus in a sea loch environment
We studied the seasonal lipid dynamics of Calanus finmarchicus from Loch Etive, a semi-enclosed fjordic
environment on the west coast of Scotland, in relation to the diapause behavior of this species. Levels of total lipid
and triacylglycerol in individual copepodid stage V (CVs) exhibited clear seasonal trends, with highest levels in
June and progressively decreasing through late summer to winter. Wax esters in CVs were more variable, but
followed a similar pattern. An index of the level of unsaturation of wax esters, effectively an indicator of the levels
of polyunsaturated fatty acids in the wax ester reserves, were highest in midsummer and declined progressively
through autumn and winter. Fatty acid analysis of total lipid in the CVs confirmed that the amounts of
polyunsaturated fatty acids in the wax esters decreased, while amounts of saturated and monounsaturated fatty
acids remained comparatively stable. Polyunsaturated wax esters are selectively catabolized by C. finmarchicus
during diapause. Previous studies have linked unsaturation of wax esters in calanoid copepods to the initiation of
diapause and buoyancy control, and we hypothesize that selective catabolism of polyunsaturated wax esters is
linked to the processes of diapause termination and ascent to surface waters.