The present study documents the seasonal biochemical composition of the nereidid polychaete Perinereis cultrifera (carbohydrates, protein, lipids, fatty acids and amino acids) collected from a shallow area on the Alexandria coast, southeast Mediterranean. The results of this study showed that P. cultrifera contained 85.34-87.76% of the wet weight as water, 14.7-20.53% of dry weight (DW) as ash, 8.3-14.84% of DW as carbohydrates, 57.33-59.9% of DW as protein and 11.59-13.36% of DW as lipids. The total fatty acids varied seasonally from 45.9 to 100% of the total lipids with the absolute dominance (37.44-91.53%) of the polyunsaturated eicosapentaenoic acid (EPA) (C20:5n-3), accompanied by a small amount of the saturate stearic acid (C18:0). Eighteen amino acids were identified, including 10 essential (59.62-61.02% of protein) and 8 nonessential (38.98-40.38% of protein).
