Fig. 3

Gross morphology of the gastrointestinal tract within ceratophryids. a. Tadpole of Chacophrys pierottii at Gosner Stage 29, ventral and dorsal views showing the abdominal cavity and the coiled gastrointestinal tube. The long intestine shows little regional specialization, with a short anterior segment that has a reticulated surface different from the intestine that is smooth with longitudinal stretches. b. Tadpole of Ceratophrys cranwelli at Gosner Stage 30, visceral morphology in ventral view. The gastrointestinal tract is shorter with differentiated anterior sac and the ampulla of the rectum. The esophagus has longitudinal folds and it is dorsal in respect to the stomach. The adult-like stomach is transparent with a “glandular” surface. c. Tadpole of Lepidobtrachus llanensis at Gosner Stage 32, the stomach occupies the half of the abdominal cavity. The gastrointestinal tract is short. The esophagus is dorsal and has longitudinal folds. The stomach has a dense pattern of glands and the gastrointestinal loop delimits the stomach from the pyloric region. The epithelium of the intestine is smooth with some aligned cells