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: 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 organogenesis of the digestive system was described in the Amazonian pimelodid catfish species Pseudoplatystoma punctifer from hatching (3.5 mm total length, TL) to 41 days post-fertilization (dpf) (58.1 mm TL) reared at 28°C. Newly hatched larvae showed a simple digestive tract, which appeared as a straight undifferentiated and unfolded tube lined by a single layer of columnar epithelial cells (future enterocytes). During the endogenous feeding period, comprised between 20 and 96 h post-fertilization (3.5 to 6.1 mm TL), the larval digestive system experienced a fast transformation with the almost complete development and differentiation of most of digestive organs (buccopahrynx, oesophagus, intestine, liver and exocrine pancreas). Yolk reserves were not completely depleted at the onset of exogenous feeding (4 dpf, 6.1 mm TL), and a period of mixed nutrition was observed up to 6 to 7 dpf (6.8 to 7.3 mm TL) when yolk was definitively exhausted. The stomach was the organ that latest achieved its complete differentiation, characterized by the development of abundant gastric glands in the fundic stomach between 10 and 15 dpf (10.9 to 15.8 mm TL) and the formation of the pyloric sphincter at the junction of the pyloric stomach and the anterior intestine at 15 dpf (15.8 mm TL). The above-mentioned morphological and histological features observed suggested the achievement of a digestive system characteristic of P. punctifer juveniles and adults. The ontogeny of the digestive system in P. punctifer followed the same general pattern as in most Siluriform species so far, although some species-specific differences in the timing of differentiation of several digestive structures were noted, which might be related to different reproductive guilds, egg and larval size or even different larval rearing practices. According to present findings on the histological development of the digestive system in P. punctifer, some recommendations regarding the rearing practices of this species are also provided in order to improve the actual larval rearing techniques of this fast-growing Neotropical catfish species.Animal : an international journal of animal bioscience. 07/2014; 8(11):1765-1776.
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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.