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Egypt. J. Exp. Biol. (Zoo.). 2012; 8(1): 67-81


MORPHOLOGICAL AND HISTOLOGICAL REMODELLING OF THE GASTROINTESTINAL TRACT OF THE TOAD, BUFO REGULARIS DURING ONTOGENY

Gamal M. Badawy Saber A. Sakr Hend T. El-Borm.




Abstract

The ontogenetic development of the gastrointestinal tract (GIT) of the Egyptian toad, Bufo regularis was described and illustrated using light microscopy from the embryonic stage up to the adult one. Seven developmental stages were mainly considered including larval i.e. 42, premetamorphic; 50, prometamorphic; 55, metamorphic; 60, postmetamorphic; 66, juvenile and adult stages, Morphometric parameters were employed for tracing the developmental changes in the GIT morphology and histology including the length, diameter, wall thickness and height of mucosal folds. Morphologically, the length of the GIT had the same attitude as the body length and exhibited progressive increase until stage 55, decreased sharply at stages 60 and 66, then increased progressively at juvenile and adult stages. The anterior portion of the small intestine exhibited more shortening than the posterior, being 89.89% and 85.97% at stage 63, respectively, after which the switchback point disappeared. At stage 66 the small and large intestinal shortenings were 91.86% and 68.42%, respectively. Histologically, the histo-morphometric analysis revealed that the diameter of the GIT increased progressively until reaching stage 55, decreased sharply at stages 60 and 66, then increased progressively at juvenile and adult stages. The wall thickness and the height of the mucosal folds of the GIT increased progressively in all the investigated developmental stages with the exception of stage 42, where the values of the height of mucosal folds were higher than stage 50 owing to the presence of the yolk. The stomach exhibited a far less remodelling trend in terms of the investigated parameters.

Key words: Ontogenetic development, Histology, Morphometry, Gastrointestinal tract, Bufo regularis






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