Biochemical and enzymatic characterization of decapsulated cysts and nauplii of the brine shrimp <i>Artemia</i> at different developmental stages

Decapsulated Artemia cysts were used to study the factors which induce the superior performance of live organisms as food for fish larvae. The biochemical composition, the in vitro protein digestibility, and the total proteolytic and trypsin activities in cysts and nauplii of Artemia were determined at different developmental stages as a function of incubation time. Six different incubation times were studied: 1, 6, 11, 16, 21 and 25h of development, which cover cyst and early nauplii stages. The individual dry weight of Artemia decreased through development. The individual protein and lipid content (µg ind-1 remained constant during development until the time of hatching after which they decreased slightly. However, no significant incubation effect was found. Small changes in amino acid and fatty acid composition were found during development, but it is assumed that they are too small to be of nutritional importance to fish larvae. No major changes were observed in protease activities measured at acid and alkaline pH during the first 25h of development. From the alkaline proteases, no significant change in trypsin activity was detected during cyst and early nauplii development. From the point of view of exogenous enzyme contribution to fish larvae, there seems to be no difference whether feeding decapsulated cysts or newly hatched nauplii, since no difference in qualitative protease composition was found during the first 25h of Artemia development. The relative contribution of Artemia proteases to the digestion of food by fish larvae is discussed