The microalga Nannochloropsis oculata is used as a diet for rotifers and can enrich the highly unsaturated fatty acid (HUFA) proportion of rotifer polar lipids (PL-HUFA). For efficient enrichment of PL-HUFAs in rotifers, we evaluated nutrient–sufficient or –deficient cell populations to clarify when the alga should be harvested and fed to rotifers. The nutrient conditions for N. oculata were spectrophotometrically monitored during cultivation and cells with nutrient sufficiency (NS) and phosphorous deficiency (PD) were harvested. The PD cells exhibited reduced chlorophyll a content, photosynthetic activity, and growth rate and accumulated total lipids as non-polar lipids (NLs). A decrease in the proportion of HUFA to total lipids between two nutrient states corresponded to a similar phenomenon observed in NLs. On the other hand, PLs, including glycolipids and phospholipids, showed different trends. Glycolipids did not change fatty acid composition between two states. Phospholipids, however, showed significantly higher contents of arachidonic acid (ArA) and eicosapentaenoic acid (EPA) only in the early periods of PD culture. It was concluded that phosphorous deficiency stimulated cells to increase the fatty acid desaturation rate of non-plastidial membranes. Mitochondria in the PD cells decreased in number but increased in size and mass. Such adaptation of mitochondria can be associated with high desaturation of non-plastidial membranes. When the early P–limited phase culture was used for the enrichment of rotifers, PL-ArA and EPA of the rotifers were enhanced by twice as much as those fed on NS cells. This study provides evidence that the beginning of phosphorous deficiency is the optimum time to harvest N. oculata cells for enhancing rotifer PL-HUFAs.

微藻Nannochloropsis oculata用作轮虫的饮食，可以丰富轮虫极性脂质（PL-HUFA）中高度不饱和脂肪酸（HUFA）的比例。为了在轮虫中有效富集PL-HUFA，我们评估了营养充足或不足的细胞群，以阐明何时应收获藻类并喂食轮虫。在培养过程中用分光光度法监测了猪笼草的营养条件，并收获了具有营养充足（NS）和磷缺乏（PD）的细胞。PD细胞显示出降低的叶绿素a含量，光合作用活性，生长速率和累积的总脂质为非极性脂质（NLs）。在两种营养状态之间，HUFA占总脂质的比例降低，这与在NL中观察到的类似现象相对应。另一方面，PL，包括糖脂和磷脂，显示出不同的趋势。糖脂不改变两种状态之间的脂肪酸组成。然而，仅在PD培养的早期，磷脂才显示出明显更高的花生四烯酸（ArA）和二十碳五烯酸（EPA）含量。结论是磷缺乏刺激细胞增加非质体膜的脂肪酸去饱和率。PD细胞中的线粒体数目减少，但大小和质量增加。线粒体的这种适应性可能与非质体膜的高度去饱和有关。当早期的P有限相培养用于轮虫的富集时，轮虫的PL-ArA和EPA增强了两倍于NS细胞。这项研究提供了证据，表明缺磷的开始是最佳收获时间N. oculata细胞，用于增强轮虫PL-HUFA。