During the early development of Artemia there is an increase in mitochondrial enzyme activities of about one order of magnitude, whereas the activities of two cytoplasmic enzymes tested as controls remain unaltered. The mitochondrial enzyme activation correlates with (i) large changes in mitochondrial morphology, (ii) a 5-fold increase in the amount of the H+-ATP synthase β-subunit and (iii) a dramatic increase in the steady-state level of mitochondrial mRNAs, whereas mitochondrial rRNA concentrations remain mostly unchanged. In contrast, the level of mitochondrial DNA does not change significantly during the first 20 h after resumption of development. After hatching, the mitochondrial DNA content increases twice in parallel with one round of cellular division, thus indicating that mitochondrial and nuclear replication are coupled in Artemia postgastrular development. The data presented strongly suggest that mitochondrial maturation in the absence of significant mitochondrial proliferation is responsible for the dramatic increase in mitochondrial function that takes place after resumption of development in Artemia.

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