SEASONAL VARIATIONS OF THE DIGESTIVE TRACT OF EGYPTIAN ROCK DOVE, COLUMBA LIVIA: ANATOMICAL, HISTOLOGICAL AND SCANNING ELECTRON MICROSCOPICAL STUDIES

This work aims to study the effect of seasonal variations on anatomical, histological, and histochemical structures of the digestive tract of Egyptian rock dove (Columba livia). The digestive tract of rock dove consists of oesophagus, crop, stomach, small and large intestine. The regions of the digestive tract of rock dove differ from each other in the type of lining epithelium, the shape of folds formed by these epithelium, the distribution of glands within their layers, finally the thickness of these layers. The oesophagealmucosa is composed of keratinized squamous epithelium which appears thicker in the crop. This epithelium becomes more compressed and converts into simple columnar and cuboidal epithelium to line the glandular and muscular stomach respectively. This simple columnar epithelium also is lining the small and large intestine, caeca and cloaca. Most glands and the goblet cells that are distributed among the mucosa of different regions of the digestive tract indicate the presence of acid and neutral mucopolysaccharide secretions while proteins are observed in the different regions of the digestive tract. The hisomorphometrical studies of the digestive tract of the rock dove during the summer and winter seasons show no significant changes on the morphological and histochemical levels of the digestive tract except the oesophagus region. The present results confirmed that the Egyptian rock dove as a resident bird doesn't often have to face environmental changes.