الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 114 |  |  |
| | | from | 114 | | |
Abstract
The present study was carried out on 151 apparently healthy mature fishes, 74 of Nile tilapia and 77 of African Catfish. They were obtained from the fish market in Beni-Suef Governorate and were transported live in dry plastic aquaria to the laboratory within 2-3 hours to allow the aerial respiration for catfishes. The weights of the Nile tilapia ranged from 175-450g and their length ranged from 19-27.5cm. While, the weights of the African catfish ranged from 175-700g and their length from 28-45cm.
These fishes were divided into 4 groups as the following:
1- Group I: Eighty-three fishes (40 Nile tilapia and 43 African catfish) were used to demonstrate the gross morphological features of their respiratory organs. The body traits measurements were recorded in Tables 1 and 2.
2- Group II: Sixty fishes (30 Nile tilapia and 30 African catfish) were used for the histological examination of the gills of Nile tilapia and catfish, as well as the dendretic organs of the catfish. The collected specimens were fixed in 10% Neutral buffered formalin or Bouin’s fluid and stained using Harries Haematoxyline and Eosin (H&E), Crossmon’s trichrom stain, Periodic Acid Schiff’s (PAS) technique, and Alcian blue (AB) technique.
3- Group III: Four fishes (2 Nile tilapia and 2 African catfish) were used for Scanning Electron Microscopy and they were examined using scanning electron microscope at Faculty of Science, Beni-Suef University.
4. Group IV: Four fishes (2 Nile tilapia and 2 African catfish) were used and small pieces of gills of Nile tilapia and catfish and the dendretic organ of African catfish. The sections were examined using Transmission Electron Microscope in the electron microscopic unit, Faculty of Science, Beni Suef University, Egypt.
The results obtained in the current study were reported as:
I- The gross examination of the respiratory organs in these species revealed that:
1- The gills constituted the main respiratory organs in Nile tilapia and African catfish. In addition to a dendretic organ which helped as an accessory respiratory organ in African catfish.
2- The shape and structure of the operculum in both species were described.
3- The gill system in both species consisted of four pairs of gills, in addition to a rudimentary fifth one in African catfish.
4- The gills were formed of crescent arches carried rakers on its concave aspect and filaments on its convex one.
5- The gill arch was cartilaginous with a groove on both sides for gill rakers and appeared thicker and slightly compressed in catfish.
6- The gill rakers were found on the concave aspect of the gill arch and they had different arrangement, length and number in the investigated fish species.
7- The gill filaments were found on the convex aspect of the gill arch. These filaments were longer in Nile tilapia. They were thinner, shorter and numerous in African catfish than in Nile tilapia. The fifth gill arch of the African catfish was devoid of filaments.
8- The dendretic organ of the catfish is a characteristic structure in this species and is responsible for air-breathing. It was located in the suprabranchial chamber caudodorsal to the gills and wholly covered by a serous membrane.
II- The scanning electron microscopy revealed that:
1- The arch was covered by numerous medium-sized polyhedral cells. Each cell was characterized by presence of multiple microplicae.
2- The gill rakers in tilapia appeared short triangular with thick wide base and tuberous free ends. While, in catfish they were numerous, cylindrical and thin.
3- The filaments of both species appeared numerous long cylindrical structures. They carried lamellae on both sides. In catfish, they were thicker than in tilapia.
4- The lamellae appeared as short papillary structures arose from the surface of the filament to increase the surface area of the filament that exposed to water. The lamellae of tilapia were thinner than that of catfish.
5- The dendretic organ appeared as highly branched structure resembling a tree or cauliflower in shape with characteristic tuberous ends. Each branch either large or small was covered by several rows separated by deep and narrow intervening spaces and each row showed numerous transversally oriented folds. In addition, many mucous cells could be recognized.
III- The histological examination of the gills and dendretic organs revealed that:
1- The gill arch in both species was formed of hyaline cartilaginous support especially at the base of the filaments. All these structures were supported by loose highly vascular connective tissue.
2- The gill rakers in both species appeared as finger-like projections consisted of a core of vascular connective tissue covered by an epithelial cap rich in mucous cells. Occasional taste buds were noticed embedded in the epithelial cap.
3- The gill filaments in both species consisted of a core of fibro-cartilaginous connective tissue rich in lymphocytes. The core of filament was covered externally by simple epithelium with focal stratification. The basal half of the filament, in both species was also supported by compact strands of striated muscle fibers arose from the gill arch. The covered epithelium of the gill filament contained mucous cells which reacted positively with alcian blue. Also PAS-positive cells could be recognized in the epithelial covering the filament.
4- The lamellae appeared as triangular short papillae formed of connective tissue core rich in blood capillaries and lymphocytes.
5- Each branch of the dendretic organ contained a central supporting hyaline cartilage surrounded by a highly vascular connective tissue and covered by stratified epithelium. The covering epithelium of the dendretic organ consisted of stratified epithelium rich in mucous alcianophilic cells.
IV- The Transmition Electron Microscopy investigation revealed that:
1- The mucous cells appeared large oval to flattened cells with elongated euchromatic nucleus, its cytoplasm rich in electron dense mucous granules and well-developed Golgi apparatus.
2- The chloride cells appeared large oval cells with oval eccentric nucleus and the cytoplasm filled with numerous rounded mitochondria with their filamentous transverse cristae.
The results obtained were illustrated in 58 figures as 18 photographs of normally dissected specimens, 20 Scanning Electron Micrographs, 18 light Microscopy Micrographs and 2 Transmition Electron Micrographs. There are some measurements of the body traits of both fish species were recorded in 2 tables.
The results obtained in this study were reported and discussed with these in the Nile tilapia, African catfish and the other fishes.
The nomenclatures used in the present study were adopted according to Zayed and Mohamed (2004), Ahmed, et al. (2008) and Helfman, et al. (2009).