The effect of starvation on RNA: DNA ratios and growth of larval striped bass, Morone saxatalis

Abstract

Hatchery reared larval striped bass, Morone saxatilis, 8‐days‐post‐hatching were subjected to various feeding/starvation regimes over a period of 14 days.Batches of larvae from each treatment were sampled over the 14‐day period and subdivided for determination of notochord length and RNA:DNA ratio. The best growth was found in fully fed F1000 larvae (exposed to 1000 Artermia nauplii l−1), which reached 8.2 mm after 11 days and 9.6 mm after 14 days. Starved animals after 11 days had notochord lengths of 4.9 mm. Growth curves from feeding‐delayed larvae indicated that animals fed after up to 5 days starvation were capable of complete recovery. F100 larvae (exposed to 100 Anemia nauplii 1−l) had a slower growth rate than F1000 larvae, reaching a notochord length of 7.3 mm after 14 days. RNA:DNA ratios over time closely followed notochord growth curves, with clear differences between starved, F100 and F1000 larvae being established after only 2 days. Equilibrium RNA:DNA ratios of 3.0 and 2.25 were established in F1000 and F100 larvae, respectively, 6.8 days after the beginning of the experiment. The average lag time between a change from the starved to the fed condition and a change in RNA:DNA ratio as determined by the divergence of the nucleic acid curve from the starved condition was 0.66 days.In treatments where starvation followed various periods of feeding, larvae regressed in notochord length such that the final length at 14 days reflected the degree of feeding. RNA:DNA ratios in these animals again closely followed growth curves with a lag time of 0.81 days.It was concluded that RNA:DNA ratios provided very accurate indices of growth in striped bass larvae which were highly sensitive to feeding status.