%0 Journal Article
%T Comparative Histomorphological and Histochemical Studies on the Oesophagus of Nile Tilapia Oreochromis niloticus and African Catfish Clarias gariepinus
%A Ashraf Sayed Awaad
%A Usama Kamal Moawad
%A Mohamed Gomaa Tawfiek
%J Journal of Histology
%D 2014
%R 10.1155/2014/987041
%X The present work aimed to describe and compare both gross and microscopic structure of the oesophagus of Nile tilapia (Oreochromis niloticus) and African catfish (Clarias gariepinus). For this purpose, 60 specimens of oesophagus of Nile tilapia (omnivorous fish) and African catfish (carnivorous fish) were collected and processed. Anatomically, the oesophagus of both species appeared as a short tube with longitudinal mucosal folds. Using scanning electron microscope, the epithelial surface of the esophagus showed primary and secondary mucosal folds in both species while tertiary folds were observed in that of tilapia only. Histologically, the oesophagus consisted of four distinct layers: mucosa, submucosa, muscularis, and serosa. The oesophageal mucosa consisted of stratified epithelium with few mucous secreting cells in catfish and many mucous secreting cells in tilapia. Two types of mucous secreting cells reacted positively with both periodic acid shiff (PAS) and alcian blue (AB); rounded and elongated cells that were recognized in the esophageal epithelium of tilapia and only elongated oval cells were observed in that of catfish. In conclusion, the obtained histomorphological differences in esophagus of both fish species may be attributed to their different feeding habits and type of food. 1. Introduction The Nile tilapia, Oreochromis niloticus, and African catfish, Clarias gariepinus, are the most important fresh water fishes in the Nile River in Egypt. According to Gafrd, [1] these two fish species have a great economic importance, where the Nile tilapia constitutes about 32% and African catfish about 17.5% of the total country catch. In this concern, Osman and Caceci [2] reported that tilapia species are the most common fishes in the Egyptian part of the Nile River. These tilapia species are well adapted to live in both fresh and brackish water at the Nile estuary at Rashid, Edku, Damietta (on the Mediterranean Sea), and Ismailia (Ismailia fork at the Suez Canal). The anatomy and histology of the digestive tract of teleostean fish have been described by many authors [3¨C9]. On the other hand, there are few studies dealing with the ultrastructure of the digestive tract. The teleost digestive tract is histologically simpler compared to mammals, probably because it is so easy to provide an aqueous vehicle for the digestive products and also because, at least in some species, the rate of digestion can be slow, and less complex digestive glands and a less well-developed muscular apparatus are needed [10]. As a part of the digestive tract, the esophagus
%U http://www.hindawi.com/journals/jh/2014/987041/