The fatty acid composition of three unicellular algal species used as food sources for larvae of the American oyster (Crassostrea virginica)

Abstract

The total lipid and fatty acid content of 3 algal species,Pyramimonas virginica, Pseudoisochrysis paradoxa andChlorella sp., which have been successful as food sources for rearing larvae of the American oyster,Crassostrea virginica, was determined. Of the fatty acids of ω6 and ω3 families which have been shown to be essential fatty acids for normal growth in many animals, only the ω6 fatty acids were found to be higher in these 3 species of algae than in the traditional oyster larvae diet which consists of the algaeMonochrysis lutheri andIsochrysis galbana. The major fatty acid constituents of the total lipids of the 3 species were the C12, C14, C16 and C18 saturated fatty acids and the C16 and C18 mono‐ and polyunsaturated acids. These components constituted 70–93% of the total lipid in cultures of all ages. There were modest amounts of C20 and C22 polyunsaturated acids; some of these existed only in trace amounts. InP. virginica andChlorella sp., hexadecanoic acid was dominant (23–39%). The presence of large quantities of tetradecanoic acid (22–26%) and oleic acid (17–21%) was characteristic ofP. paradoxa. Chlorella sp. had the highest proportion of octadecatrienoic acid (18∶3ω3) which accounted for up to 17% of the total lipids. γ‐Linolenic acid (18∶3ω6) was found only inChlorella sp., but in the 5th‐day culture only. The lowest proportion of total polyethylenic acid was inP. paradoxa; however, lipid analyses showed this alga had the most lipid/individual cell. Some variations were observed in the fatty acid composition with age of the culture.

Total fatty acid composition as a taxonomic index of some marine microalgae used as food in marine aquaculture

“…Chlorella species are the most controversial algae in the literature with respect to total lipid fatty acid composition. Chu & Dupuy (1980), Ben-Amotz et al (1987, Rezeq (1988), andJames et al (1989), present fatty acid distributions for Chlorella species quite similar to those described by us, with high PUFA levels, mainly composed by 16: 2n-6, 16: 3n-3, 18: 2n-6, and 18: 3n-3. On the contrary, Watanabe etal.…”

Particulate lipid class composition of three marine phytoplankters Chaetoceros gracilis, Isochrysis galbana (Tahiti) and Dunaliella tertiolecta grown in batch culture

“…Interest in algal production of economically important molecules such as lipids has increased in the past few decades, mainly due to applications in aquaculture, where various phytoplankton species are used as food for larval and adult molluscs (Chu & Dupuy, 1980). One of the more common food choices for American oyster larvae, the flagellate Isochrysis galbana, also produces high levels of the unsaturated fatty acid 22: 6w3 (Enright et al, 1986).…”

Sources of C20-polyunsaturated fatty acids for biotechnological use

“…Such fatty acids are essential for the nutrition of the edible marine animals to be reared (Langdon and Waldock 1981;Enright et al 1986). The level of these compounds in the diet is one of the major factors affecting their nutritional value (Chu and Dupuy 1980;Watnabane et al 1980;Dosanjhi et al 1988). …”

“…However, algae such as Pyramimonas virginiea, Chlorella sp. and Pseudoisochrysis paradoxa (Chu and Dupuy 1980) and Skeletonema costatum, Chaetocaros gracilis and Tetraselmis chuii (Suet al 1988), which are suitable for rearing aquatic animals, contain considerable proportions of C2o-and C22-polyunsaturated fatty acids. Reportedly, S. costatum may contain up to 43% eicosapentaenoic acid (20:5) of the total fatty acids.…”