PMC

A schematic diagram of the intestine from the anterior to the posterior is shown on the left (dashed lines indicate the boundaries of typhlosole with the intestines). On the right of each panel shows representative MGPY-stained cross-sections of the intestine from indicated regions of the intestine of premetamorphic tadpoles at stage 54. In the middle is a schematic drawing of the cross-section showing the presence or absence of the typhlosole. Note the presence of the typhlosole in the posterior half of the small intestine in X. tropicalis but not X. laevis.

Histological structure of the hindgut epithelium in the anterior chamber and papillate region. A Ventral-lateral epithelium in the anterior chamber B Apical parts of ventral and lateral epithelial cells are bulging into the hindgut lumen C Dorsal epithelium in the anterior chamber forms typhlosole (T) and two typhlosole channels (TC) D Epithelial cell of typhlosole E Epithelial cell of typhlosole channel F Hindgut epithelium in the papillate region G Basal parts of epithelial cells in the papillate region are bulging into haemocoel. Abbreviations: M – muscles, N – cell nucleus.

Stage 54 X. laevis or tropicalis tadpoles were treated with 10 nM T3 at 18°C (Xenopus laevis tadpoles) or 25°C (Xenopus tropicalis tadpoles) for the indicated days and the intestine was isolated. The length of the typhlosole and the small intestine were measured. Note that the lengths of the intestine was reduced upon T3 treatment and that after 4–5 days of treatment, the typhlosole was no longer identifiable due to metamorphic changes in the intestine, resembling that at the climax of metamorphosis. The faster changes for X. tropicalis tadpoles were in part due to the higher temperature at which the animals needed to be reared.

Fig. 7. Eisenia koreana (Zicsi, 1972) typhlosole. dv = dorsal vessel.