Dietary lipid changes during herbivory and coprophagy by the marine invertebrate Nereis diversicolor

Changes in dietary lipids (fatty acids, sterols and fatty alcohols) during herbivory and coprophagy by the annelid worm Hediste (Nereis) diversicolor (O.F. Muller) were modelled in laboratory feeding experiments. The dinoflagellate Scrippsiella trochoidea (Stein) was used as the food in herbivory; faeces from the crustacean Neomysis integer (Leach) after feeding on this same alga, were used as the food in coprophagy. Nereis is extremely efficient in its assimilation of dietary lipids and produces faeces with very low fatty acid:sterol (FAST) ratios in both herbivory and coprophagy. The net decrease in total lipid in both modes of feeding with this species suggests that annelids, where present, are as important as other invertebrate groups in affecting the flux of lipids through marine food chains.