The potential of liposomes as a nutrient supplement in first-feeding marine fish larvae

The ingestion rate (ng liposome larva^-1 h^-1) of extruded [1-¹⁴C] palmitic acid-labelled liposomes containing physiological saline (PHS) or cod fish extract (CFE), was tested in 5-day-old gilthead seabream Sparus aurata and white grouper Epinephelus aeneus larvae. A follow-up study compared the assimilation of radioactive free fatty acid (FFA) label of these two liposome treatments into six phospholipid and neutral lipid fractions as well as the nonlipid fraction in 5- day-old seabream. In seabream larvae, there was a 50-fold (P < 0.05) increase in the net consumption rate when fed CFE liposomes (2305.8 ng liposome larva^-1 h^-1) compared with liposomes containing physiological saline (42.7 ng liposome larva^-1 h^-1). A similarly significant (P < 0.05) but less marked pattern was also observed in the grouper larvae where the CFE treatment larvae ingested 238.5 ng liposome larva^-1 h^-1 compared with 54.3 ng liposome larva^-1 h^-1 in larvae fed the PHS liposomes. In seabream larvae ingesting CFE and PHS liposomes, radioactivity was found in all larval fractions analysed. However, marked treatment differences (P < 0.05) in assimilation were found only in the triacylglycerol fraction (3.4 and 0.6 dpm larva^-1 h^-1, respectively) and nonlipid fraction (11.2 and 15 dpm larva^-1 h^-1, respectively).