Microalgal solutions in the cultivation of rotifers and artemia: scope for the modulation of the fatty acid profile

The microalgae Aurantiochytrium sp. (AUR), Isochrysis sp. (ISO), and Nannochloropsis sp (NAN) were studied as possible alternative feeds to well established commercial compound feeds for both rotifers (Brachionus plicatilis) and Artemia franciscana. Fatty acid (FA) composition —relative (in % of total FAs) and absolute (in mg/g dw)—was determined in order to assess their potential for providing essential FAs. The FA profiles showed relevant differences between the four feeds (compound feed and the three microalgal species), but less stark than in the feeds themselves. Whereas Isochrysis sp. was relatively rich in DHA and poor in EPA, 18.6 ± 1.7% vs 0.6 ± 0.0%, respectively, Nannochloropsis sp. had the opposite pattern, 0.2 ± 0.3% vs 28.3 ± 0.7%. Aurantiochytrium sp. was rich in DHA (19.1 ± 0.2% corresponding to 89.8 ± 0.2 mg/g dw), but posed difficulties as a feed for both rotifers and artemia, given its low lipid incorporation and, in particular, poor DHA deposition. Rotifers fed the compound feed had the best combination of n3 PUFA levels (22.1 ± 0.1 mg/g dw), DHA contents (13.6 ± 0.4 mg/g dw), and DHA/EPA ratios (~3), being rotifers fed AUR and ISO feeds second best. Hence, these microalgae may deserve to be further explored as potential sources of specific FAs in rotifers and artemia.