Ontogenetic changes in DNA and RNA content of laboratory-reared Prochilodus lineatus larvae: use of RNA/DNA ratios as indicators of nutritional condition

Abstract

The aims of the present study were to describe the ontogenetic performance of DNA and RNA content, as well as to assess the nutritional condition of Prochilodus lineatus larvae reared under different feeding treatments. The experiment consisted of two parts, the first 6-14 days after hatching (DAH) and the second 15-21 DAH. In the first part of the experiment, larvae were kept under one of two feeding treatments: fed or starved. During the second part of the experiment, larvae were kept under one of four treatments: fed, fed until 14 DAH and later starved, starved until 14 DAH and fed later or starved. It is of note that the size and weight reached of larvae that were starved during early development and later received food were higher than those of than larvae in the other feeding treatments. In addition, instantaneous growth rates were higher and nutritional condition was better in larvae that were initially starved and fed later. The availability of food following a period of starvation seems to trigger larval metabolism and cellular division. Consequently, we recommend maintaining appropriate food provision in the aquaculture of P. lineatus larvae, especially in advanced developmental stages. We verified that RNA/DNA ratio is affected by the feeding condition and that it is sensitive enough to promptly reflect changes in feeding conditions of P. lineatus larvae. Thus, the RNA/DNA ratio could be used to assess nutritional condition of both wild and cultured P. lineatus larvae.