DNA, RNA, Protein, and Free Amino Acids During Ontogenesis of Rainbow Trout (Salmo gairdneri)

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Abstract
During the first 2 wk of incubation, the pattern of change in DNA concentration tended to precede similar changes in RNA concentration. Unfertilized eggs contained 23.2 and 77.2 μg of DNA and RNA, respectively. DNA concentration rose from 155.8 μg/fry (after 23 days of incubation) to 326.6 μg/larva (14 days after hatching), while RNA increased from 238.8 to 693.3 μg during the same period. Protein per ontogenetic unit was relatively constant during the prehatching stages but dropped markedly just prior to hatching. Of the protein in the unfertilized egg, approximately 20% was retained in the fry at hatching and approximately 50% was retained in the larva following yolk absorption. Total free amino acid concentrations declined just after fertilization, indicating the initiation of protein synthesis or a decline in yolk protein degradation. These concentrations increased to near initial values in the blastula and were nearly doubled in the yolk plus fry at hatching.