Changes in plant lipids during passage through the gut of Calanus

By means of capillary gas chromatography (GC) and capillary gas chromatography'mass spectrometry (GC/MS), the aliphatic hydrocarbons, fatty acids, fatty alcohols and 3s-sterols were identified in saponified lipid extracts of the green alga, Dunaliella primolecta , the copepod, Calanus helgolandicus , and faecal pellets released by the animal when fed in the laboratory on the algal diet. Comparison of the lipid data for faecal pellets with those for the plant showed that marked changes to dietary lipids occur during passage through the gut of the copepod: (1) 17:2, 17:1, and 17:0 hydrocarbons are completely eliminated; (2) polyunsaturated fatty acids (e.g. 16:4 and 18:3) are significantly reduced relative to total fatty acids; (3) evidence of the conversion of phytol to dihydrophytol is observed; (4) C28 and C29 sterols with Δ and Δ nuclear unsaturation are selectively removed from the diet relative to Δ components. The Δ sterols are released unchanged as faecal lipids. Cholest-5-enol, absent from the original diet, is also released in the faecal pellets. These observations illuminate the fate of specific dietary lipids in Calanus and the contribution copepod faecal pellets can make to the overall lipid composition of bottom sediment in many marine environments.