The development of the digestive tract in larval European catfish (Silurus glanis L.).
ABSTRACT The European catfish, Silurus glanis L., has become an important aqua cultural fish in Croatia, and it is cultivated extensively in ponds in polyculture with carps. The development of the digestive tract in S. glanis was studied with the aim of improving intensive fish production. Research was carried out on S. glanis larval stadium from 1- to 19-day post-hatching (DPH). The main histological methods used were: haematoxylin and eosin staining, periodic acid Schiff staining (PAS), Alcian blue (AB) and toluidin blue staining (TB). A yolk sac was present during the first 5 days (1-5-DPH). During the initial 3-DPH period, there was no trace PAS and AB activity in the digestive tract. Differentiation of the digestive tract began at 3- to 5-DPH. The oesophagus was positive for AB at 5-DPH, PAS and TB after 7-DPH. Differentiation of enterocytes began at 5-DPG and the intestines were complete at 11-DPH. Development of liver and pancreas was also studied. The analysis of data obtained in this study suggests that after 5-DPH catfish larvae have morphologically completed digestive tracts.
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ABSTRACT: In this work, histological and histochemical features of the larval digestive system of Argentine anchovy Engraulis anchoita were described. Structural changes during ontogenetic development were also characterized, and comparisons between the beginning and the end of larval development were made. Histological sections of larvae were subjected to histochemical and routine histological techniques to localize and differentiate glycoproteins (GPs). Both at an early and a late larval stage, the oesophageal goblet cells reacted more intensely than those of the rest of the digestive tract, and only the oesophagus exhibited metachromasia with toluidine blue techniques at different pHs, thus revealing diverse GPs at different concentrations. The GPs histochemical composition in the intestine varied with the developmental stage and the intestinal zone. The absence of goblet cells characterized the foregut; however, they started differentiation at an advanced stage in the midgut. These cells could be detected in the hindgut both at the beginning and at the end of development. The attached glands showed a varied glycoprotein composition. The digestive tract of E. anchoita presented a high level of complexity, related to the multiple functions of mucus in the digestive tract, such as lubrication, protection, antimicrobial function and ionic and osmotic regulation.Acta Zoologica 06/2013; · 1.47 Impact Factor
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ABSTRACT: The histological development of the digestive tract and accessory organs of Nieuhofii's walking catfish, Clarias nieuhofii from hatching until 46 dah (day after hatching) was described using light microscopy. The mucosubstances and the liver glycogen were histochemical studied. At hatching, the digestive tract of C. nieuhofii was composed of a straight tube lining with the simple low columnar epithelium. Undifferentiated liver and pancreas cells were found just after hatching for 36 and 48 hrs, respectively and the glycogen in hepatocytes were observed at 3 dah. The opening of mouth and anus occurred at 2 dah, with distinct structure of esophagus, stomach, and intestine. By 3 dah, the buccopharygeal tooth bud was found coinciding with the stratification of esophageal epithelium with acid mucosubstance. At 5 dah, the yolk sac was not morphologically noticeable and yolk completely depleted by dah 7, indicating the end of endogenous feeding, while the onset of endo-exogenous feeding of C. nieuhofii was between 4-7 dah. By 4 dah, the first gastric gland appeared in mucosa of stomach and from this moment onwards several rapid histological changes of the digestive tract occurred in term of increasing in size of organ and number of cell structure with fish age to the end of investigation (46 dah). This study provides a basis for the optimization of formulated feeding during larval culture of this species. Background The Nieuhofii's walking catfish, Clarias nieuhofii is the freshwater catfish in the family Clariidae, order Siluriformes. Due to its tender flesh and good flavor, C. nieuhofii has been targeted to be a commercially important fishery as human food, as well as to increase production of C. nieuhofii fingerling for stocking to natural waters through aquaculture as the population of this catfish in nature is being decline. Basically, rearing of fish larvae is an extremely important issue from the commercial point of view, since it is the only way of successful reproduction of fish. The process of yolk sac resorption and exogenous initial feeding is a critical period as from this moment onwards, coinciding with the morphological changes of digestive tract, this transition is important as a source of larval growth and survival . Histological analysis is essential for the accurate determination of the functional relationship between feeding and absorption of nutrients at the time of start exogenous feeding through fish larval life . As the basic knowledge of development in digestive system of C. nieuhofii is limited, and with the marked diversity in morphology and function of digestive tract in fishes, thus the purpose of this study was to describe the ontogenic development of the digestive tract in this species for the use of improving management in rearing conditions and to provide a basis for the optimization of formulated feeding during larval culture.
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ABSTRACT: The morphology of the farmed African catfish distal intestines and rectum was investigated. The samples were dissected out and the tissue slices were passed through graded ethanol, cleared in xylene, embedded in paraffin wax, sectioned and stained for light microscopy. Grossly, the intestine was subdivided into proximal, middle, distal and rectal regions based on palpable thickness and diameter of the regions. No intestino-rectal valve was observed; hence the rectum was not well defined. The histology revealed the presence of tunica mucosa of simple columnar cells, lamina propria of collagen fibres and muscularis mucosae of smooth muscle fibres; submucosa of loose connective tissues and blood vessels; tunica muscularis of smooth muscles in an inner circular and outer longitudinal arrangement; and a serosa in all regions except the rectum and anus that presented tunica adventitia. The mucosal folds were fingerlike to orange leaf shaped ingrowths into the lumen on a transverse section. They decreased in complexity and height but increased in width towards the rectum. The lining epithelium of the intestinal tract was comprised of the absorptive simple columnar cells containing goblet cells and intraepithelial lymphocytes. Some rectal simple columnar epithelium contained supranuclear vacuoles while others contained non-vacuolated cytoplasm. The goblet cells contained neutral and acid mucins, and increased in number progressively towards the rectum. The anal tunica muscularis contained mostly skeletal muscles. Key words: histology, histochemistry, intestine, farmed African catfish.Journal of Agricultural Sciences. 08/2014; 59(3):287-300.