Diacronema vlkianum was grown in polyethylene bags at two different temperatures (18 and 26A degrees C) in the laboratory. The biochemical composition level decreased when the temperature increased from 18 to 26A degrees C. The maximum cell number at 18A degrees C was 11.9 x 10(6) cells ml(-1), while maximum cell number at 26A degrees C was 1.6 x 10(6) cells ml(-1). The maximum level of alpha-tocopherol was 257.7 +/- A 21.6 mu g g(-1) dry weight (DW) at 18A degrees C. The highest total carotenoids and chlorophylls were 6.5 mg g(-1) DW and 4.3 mg g(-1) DW, respectively, and the main pigments were determined as astaxanthin and lutein. Polyunsaturated fatty acids were found to be the predominant group, reaching 39.5% of the total fatty acids at 18A degrees C. This comprised 20:5(n - 3) as the main polyunsaturated fatty acids (20.4%, at 18A degrees C) followed by 22:6(n - 3) (4.8%, at 18A degrees C). The results suggest that D. vlkianum can be successfully used as feed in shellfish hatcheries or aquaculture hatcheries, either as a substitute or in association with other microalgae, when this algae is cultured at 18A degrees C.