- Abstract The chlorophyte Haematococcus pluvialis accumulates large quantities of astaxanthin under stress conditions. Under either nitrogen starvation or high light, the proportion of each picogram of astaxanthin was accompanied by that of 5 or 3–4 pg of fatty acids, respectively. In both cases, the newly formed fatty acids, consisted mostly of oleic (up to 34% of fatty acids in comparison to 13% in the control), palmitic and linoleic acids, were deposited mostly in triacylglycerols. Furthermore, the enhanced production of oleic acid was linearly correlated with that of astaxanthin. Astaxanthin which is mostly monoesterified, is deposited in globules made of triacylglycerols. We suggest that the production of tailor-made oleic acid-rich triacylglycerols on the one hand and the esterification of astaxanthin on the other hand, enable the oil globules to maintain the high content of astaxanthin esters.