Post mortem changes in the concentration of free amino acids in Artemia franciscana at different temperatures

Post mortem proteolysis of Artemia franciscana in terms of free amino acid (FAA) concentrations was determined at several temperatures to indicate potential nutritive value. The experiment was conducted for 400 min at 12, 16, 20, 24 and 28 °C to correspond to gut passage times and temperatures expected in the gut of cold-water fish larvae through tropical fish larvae. After death, FAA concentration in A. franciscana nauplii reached a maximum about 2–2.5-fold higher than the initial concentration after 120 min at 16, 20, 24 and 28 °C. At 12 °C the maximum concentration of FAAs was achieved after 240 min. A significant effect of temperature on total FAAs (df = 4, F-value = 17.17, P < 0.0001, ANOVA), indicated that the most pronounced proteolysis took place at 20 °C. Only small, albeit significant (P < 0.05) differences were observed in FAA composition as influenced by temperature and duration of the proteolysis. The FAA composition of the freshly killed initial sample also differed from all treated samples. Our interpretation of these results is that there is considerable autolytic proteolysis during residence times that are possible in fish larvae, and that this may represent a significant contribution to FAAs for energy supply and protein synthesis.