Nutritional cellular biomarkers in early life stages of fish.

Histological (tissular and cellular) indices have a tradition of determining the nutritional condition of fish both in the laboratory and in the wild. The assessment of condition by means of microscopical methods is probably the mos accurate indicator of nutritional status during the early life stages of fish. This success is partly attributable large amount of information that can be derived from their study and because they are thought to be the only true starvation indices. The technique usually consists of the examination of cells and organs and the establishment of a grading system based on the presence/absence of standardised biomarkers. Each organ is examined, and the cellular aspect or tissular cohesion is evaluated qualitatively and even quantitatively in order to obtain a measure of the general condition of a larva. The literature indicates that there are certain tissular and cellular responses to food availability and quality, particularly in the digestive and muscular tissues, which are common to most teleost fish larvae. These responses, which are independent of water temperature, can be used for assessing fish larvae nutritional condition. In this regard, the microscopical organization of the liver hepatocytes, the intestinal mucosa, the exocrine pancreas and the muscular fibers, which are generally used as target tissues and organs to assess the nutritional condition of fish larvae, is deeply reviewed. The advantages and disadvantages of the use of different cellular biomarkers of effect are discussed considering different conditions.