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The inclusion of phosphatidylcholine (PC) in a purified diet is essential for the survival of juvenile lobsters. Attempts to substitute this substance with its alkaline hydrolysis products, fatty acids, an emulsifier or other phospholipids (cephalin, phosphatidylinositol) were not successful. The effectiveness of the PC ingredient in reducing mortality related to a molt death syndrome is dependent upon the source of the compound. Those PC molecules comprised of polyunsaturated fatty acids, were most effective. The lobster's nutritional requirement for PC is probably the result of a low rate of biosynthesis and the physiological role of PC is more probably associated with hemolymph lipoproteins and the transport of lipids, possible cholesterol.

Two experiments were conducted to develop a purified diet suitable for studying nutritional requirements of juvenile white sturgeon (Acipenser transmontanus). In the first experiment, growth and survival rates of fish fed a purified diet (SPD) containing 50% casein:wheat gluten:egg white (6.2:3.0:0.8) and 8% refined soy lecithin were significantly (P less than 0.05) better than those fed a commercial nonpurified rainbow trout diet, a purified rainbow trout diet containing 50% casein:gelatin (7:3) or a purified catfish diet containing 34% spray-dried egg white. In the second experiment, fish fed SPD diet with or without cholesterol but with the same amount of lipid grew equally well. Fish fed SPD diet with lecithin grew significantly better than those fed SPD diet with its 8% lecithin replaced with an equal amount of an oil mixture. In both experiments, fish with good growth and survival rates also had significantly lower body moisture and higher protein and lipid contents than fish with poor growth and survival rates. Results suggest that the SPD diet with lecithin and without cholesterol (SPD-C) is a suitable purified diet for juvenile white sturgeon.

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Pigmentation of cultured lobsters is dependent upon the presence of dietary carotenoids. Inclusion of pure or crude carotenoids in a purified diet results in the accumulation of exoskeleton pigments tentatively identified by thin-layer chromatography and spectrophotometric analysis as primarily astaxanthin and β-carotene. Despite the lack of de novo synthesis pure carotenoids such as β-carotene, echinenone, and canthaxanthin are transformed into astaxanthin. The level of pigmentation produced by these biosynthetic precursors is related to the proximity to the astaxanthin end product. A carotenoid extract from crayfish waste dissolved in cod liver oil, and oleoresin paprika were effective in producing pigmentation. Rationale for the choice and use of carotenoid sources for incorporation into artificial feeds to produce natural pigmentation of cultured lobsters is discussed.