Storage lipids of the copepod Calanus finmarchicus from Georges Bank and the Gulf of Maine
Limnol. Oceanogr., 43(3), 1998, 488-497 | DOI: 10.4319/lo.1998.43.3.0488
ABSTRACT: Storage lipids of fifth copepodites (C5) of Calanus finmarchicus from Georges Bank and the Gulf of Maine were quantified from video images and by Iatroscan (thin-layer chromatography with flame-ionization detection, FID). Oil withdrawn from the oil sac by micropipette was pure wax ester (WE); triacylglycerols (TAG) were elsewhere in the body. Video images indicated more WE than could be demonstrated by Iatroscan. This was due to greater FID response to pure, commercially available waxes with low levels of unsaturation than to mixtures of mostly polyunsaturated wax in C. finmarchicus. A revised calibration scheme uses both WE and TAG purified in bulk by silica gel chromatography from C. finmarchicus itself. Use of quadratic calibration curves allowed analysis of single specimens, showing the individual variability of lipid class composition. C5 collected in April-July, while presumably storing lipid for the resting stage, showed a nearly constant level of TAG, ~17 µg ind.-1, whereas WE amounts varied from nearly 0 to >300 µg ind.-1. There appears to be a TAG quota that is filled before WE accumulates significantly and that is usually not exceeded. Many C5 collected in February and March had very high amounts and fractions of TAG. This likely results from transformation of stored WE to TAG in preparation for egg production.