beta-Hydroxybutyrate in developing nauplii of brine shrimp (Artemia franciscana K.) under feeding and non-feeding conditions

Body content of beta-hydroxybutyrate, and individual dry mass, carbon content, and survival rate, were studied in developing nauplii of the brine shrimp Artemia franciscana K. from hatching to 96-97 h post hatching at 27 +/- 1 degrees C. The effect of two diets was studied in the experiment: Super Selco (SS) with a high lipid content; and Protein Selco (PS) with a high protein content. A starving group (S) was used as reference. The level of beta-hydroxybutyrate at hatching was 0.6 nmol.ind-1; it increased to 1.0-1.5 nmol.ind-1 in the SS- and S-groups, while in the PS-group it remained stable between 0.6-0.8 nmol.ind-1. At 60-80 h post hatch in the SS- and S-groups, the levels of beta-hydroxybutyrate were similar to the initial levels. The survival rate remained higher than 95% until 24 h post hatching in all groups. At the end of the experiment, the survival rate was 63% in the PS-group, 13% in the S-group and 3% in the SS-group. The Artemia nauplii individual dry mass and carbon content remained relatively stable in the SS-group; both parameters showed a significant increase in the PS-group and a significant decrease in the S-group. The results suggest that Artemia nauplii utilise ketone bodies as a fuel during development and growth, but that ketone catabolism may be overloaded by excessive lipid feeding resulting in increased mortality and possibly a ketotic acidosis.