The development of midgut, liver and pancreas bullfrog tadpoles (Rana catesbeiana) fed commercial diets with 22, 24 or 28% of crude protein (CP) was evaluated. A total of 360 tadpoles, 15 days old, from the same spawning, was allotted to 30 L-boxes, using a density of 1 tadpole/L, kept at 25 °C (±1°C). A completely randomized experimental design with four replications was used. Three tadpoles of each group were collected from 9th to 48th day of feeding, and organs (midgut, liver and pancreas) were fixed in Bouin's solution and staining by Hematoxilyn and Eosine. The presence of extremely loose connective tissue in the intestinal loops of tadpoles suggested temporary situation for the change of the architecture after metamorphosis. During this period, there was an increase in goblet cells and microvilli numbers, and in the 25th day, it was observed presence of liver cells, with more compact glandular arrangement, suggesting functionality and confirms the best performance results obtained from that period in tadpoles fed diets with the highest protein level. On the 35th day, it was observed structure of bilobade liver, with signs of disorganization, which indicates rarefaction cell protein, due to poor use of dietary protein. Further studies are needed to continue the clarification of the physiological characteristics of bullfrogs during the tadpole phase.
animal nutrition; frog culture; histology
