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An increasing number of studies suggest that DHA associated with dietary phospholipid (PL) is better metabolically available for fish larvae. Knowledge on how to increase DHA levels in the major PL classes of the live feed is needed. Brachionus Cayman was cultured in conical fibreglass vessels, enriched with commonly used commercial diet Multigain or DHA Selco (DSelco) in flat bottom vessels at 20 °C. The changes of DHA content in the PL of the rotifers through enrichment and through a starvation phase post-enrichment were investigated in order to define an appropriate enrichment time and to test the stability of DHA post-enrichment. The different dietary non-HUFA (non-highly unsaturated fatty acid) composition of DSelco (25.1% SFA, 32.1% MUFA) and Multigain (40.7% SFA, 2.11% MUFA) allowed an evaluation on how SFA and MUFA might affect the efficiency of DHA enrichment of phospholipid in the rotifers. Rotifer samples were collected at 0 h, 1 h, 2 h, 4 h, 8 h, 12 h and 24 h after initiation of enrichment. Total lipid (TL) and the fatty acid composition in TL, phosphatidylcholine (PC) and phosphatidylethanolamine (PE) of rotifers and enrichment diets were analysed. The highest DHA levels in PC (23.0%) and PE (16.5%) in Cayman were found after 24 h enrichment with Multigain, and levels were far higher than obtained earlier. The enriched DHA was stable at 10 °C for at least 24 h post-enrichment under starving conditions ( p > 0.05), whereas a significant ( p < 0.05) decrease of DHA was observed during starvation at 20 °C. In order to obtain high DHA levels in PC and PE in rotifers, the enrichment time is suggested to be at least 24 h to maximise the efficiency of DHA enrichment in PL and the enrichment diet should have a high DHA content. The feeding rations should be low to reduce the total lipid contents of the rotifers. The overall results allowed us to propose a hypothesis that 18:1n9 can inhibit DHA incorporation through competition whereas 16:0 can facilitate DHA incorporation into PL. The hypothesis needs to be further tested. Statement of relevance The paper is bringing information about fatty acid enrichment of rotifers in questions that are so far quite unclear and could have a strong impact on larviculture of marine fish larvae. This study shows methods to obtain high level of DHA in phospholipids of rotifer. The results could potentially have a significant impact to improve current fatty acid enrichment protocols for rotifers. [ABSTRACT FROM AUTHOR]

This paper reports the positional distribution of fatty acids in triacyl-sn-glycerols (TAG) of Artemia franciscana nauplii. The nauplii were enriched for 4 to 24 h with fatty acid ethyl esters (EE) and TAG prepared from two fish oils, bonito head oil and cod liver/mackerel oil. TAG isolated from the enriched Artemia nauplii were subjected to stereospecific analysis in order to determine the content of each fatty acid in the sn-1, sn-2 and sn-3 positions. In TAG of the enriched Artemia nauplii (24 h), docosahexaenoic acid (DHA) was esterified in the sn-3 position (5.0–35.0 mol%) in preference to the sn-1 position (0.7–7.3 mol%) and sn-2 position (1.0–10.4 mol%). Eicosapentaenoic acid (EPA) was preferentially esterified in the sn-2 position (10.2–12.8 mol%) followed in sequence by the sn-3 position (6.4–8.8 mol%) and sn-1 position (2.5–5.8 mol%). The Artemia nauplii tended to attract 18:1 and 18:0 fatty acids to the sn-1 position, EPA and 16:0 to the sn-2 position, and DHA, 22:1, and 20:1 to the sn-3 position of their TAG. The positional distribution of fatty acids in the dietary fish oils TAG was not held in the Artemia nauplii. Once fatty acids are released from dietary fish oils EE and TAG, these fatty acids seem to be incorporated into Artemia TAG in a consistent manner independent of their origin, fish oils EE or TAG. [Copyright &y& Elsevier]

This paper reports the positional distribution of fatty acids in triacyl-sn-glycerols (TAG) of rotifers Brachionus plicatilis enriched with marine oils TAG. The rotifers were enriched with fish and seal oils TAG for 4–24 h, and TAG isolated from the enriched rotifers were subjected to stereospecific analysis in order to determine the content of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) in the sn-1, sn-2 and sn-3 positions of the TAG. In rotifers enriched with fish oil TAG, DHA was esterified in the three positions of TAG with the distribution patterns of sn-2 (highest)>sn-3>sn-1 (lowest) positions (4- and 8-h enrichments), sn-2&ap;sn-3>sn-1 positions (12- and 18-h enrichments) and sn-3>sn-2>sn-1 positions (24-h enrichment). In rotifers enriched with seal oil TAG, DHA showed a consistent pattern of sn-3>sn-1>sn-2 positions (4–24 h). EPA in the 24-h enriched rotifers showed the patterns of sn-3>sn-2&ap;sn-1 positions (fish oil TAG enrichment) and sn-3>sn-1>sn-2 positions (seal oil TAG enrichment). In the seal oil TAG enrichment, distribution patterns of DHA and EPA were similar between the dietary TAG and rotifers TAG. In contrast, distribution patterns of these fatty acids in the fish oil TAG (sn-2>sn-3>sn-1 positions) were not entirely held in the enriched rotifers. [Copyright &y& Elsevier]