Digestive gland structure as a feed index for juveniles of the queen conch, Strombus gigas, reared with formulated food

摘要

One of the bottlenecks for the queen conch, Strombus gigas, aquaculture is the lack of well-adapted formulated food for optimal growth. The goals of this study were to analyse the digestive gland structure of conchs fed with different diets using histochemical techniques and to evaluate the growth and survival of S. gigas juveniles with nine formulated diets (protein from 190 to 380 g kg−1 and lipids from 26 to 82 g kg−1). Proteoglycan granules and acidophilic granules were detected in the digestive cells. The abundance of both granule types was variable, according to the nutritional state of the animals. The granular content of the digestive cells of conchs fed with artificial diets was scarce when compared with conchs fed on natural food. Of the nine formulated feeds, the diet with 365 and 45 g kg−1 of protein and lipids, respectively, gave the best growth in weight (0.20 g day−1) and was also associated with digestive cells in the best condition as determined histologically. Histochemical analysis of the digestive gland differentiated with Alcian blue staining determines the nutritional status much better than a simple growth index and is therefore more useful in assessing adjustments to the feed formulation to meet the real needs of conchs.