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Not AvailableHeteropneustes fossilis (Bloch) is an important candidate species for diversification of freshwater aquaculture in India. However, high mortality rate during larval rearing is the most serious bottleneck in commercial production of this species. A proper understanding of the ontogenic development of digestive system provides the basis to understand the nutritional physiology of larvae and develop appropriate feeding strategies. In the present study, the ontogenical development of the digestive tract in H. fossilis larvae was studied from hatching until 30 day post-hatching (dph) at 29 °C. At hatching (2.8 ± 0.2 mm standard length, SL), the digestive tract was undifferentiated and attached dorsally to the yolk sac. At 1 dph (2.9 ± 0.2 mm SL), the mouth opened and oral valves were visible. At 2 dph (3.0 ± 0.3 mm SL), goblet cells were observed in the buccoparyngaeal cavity. At this age, exogenous feeding started and the intestine was differentiated into the anterior and posterior regions, and the rudimentary liver and pancreas were also seen. Small supranuclear vacuoles were observed in the enterocytes of the posterior intestine at 2 dph. Zymogen granules were observed in acinar cells of pancreas by 3 dph, and islets of Langerhans were visible at 4 dph (3.5 ± 0.1 mm SL). At the same age, most of the yolk sac reserves were consumed, whereas they were completely exhausted by 5 dph (3.9 ± 0.5 mm SL). Between 4 and 6 dph, the liver elongated in size and started to accumulate lipids in the hepatocytes. Gastric glands were detected at 4 dph, and the pyloric sphincter was completely differentiated at 9 dph (6.1 ± 0.4 mm SL) as an epithelial fold that separated stomach from the anterior intestine. By 13 dph (8.6 ± 0.2 mm SL), profuse gastric glands were visible inside longitudinal mucosal folds of the stomach. The formation of gastric glands and their development were noticed as the last events in the development of the digestive tract in H. fossilis. This indicated the end of the larval period and the commencement of the juvenile stage. Considering these observations, it is suggested that H. fossilis larvae have a morphologically complete digestive tract by 13 dph. The findings of the study on the development of the digestive system in H. fossilis may help in synchronising the larval stage of development and feeding strategies and would be helpful in improving larval rearing techniques for catfish species.Not Availabl

Not Available

Not AvailableHeteropneustes fossilis (Bloch) is an impor-tant candidate species for diversification of freshwateraquaculture in India. However, high mortality rate dur-ing larval rearing is the most serious bottleneck in com-mercial production of this species. A proper understand-ing of the ontogenic development of digestive systemprovides the basis to understand the nutritional physiol-ogy of larvae and develop appropriate feeding strategies.In the present study, the ontogenical development of thedigestive tract in H. fossilis larvae was studied fromhatching until 30 day post-hatching (dph) at 29 °C. Athatching (2.8± 0.2 mm standard length, SL), the diges-tive tract was undifferentiated and attached dorsally tothe yolk sac. At 1 dph (2.9 ± 0.2 mm SL), the mouthopened and oral valves were visible. At 2 dph (3.0 ±0.3 mm SL), goblet cells were observed in thebuccoparyngaeal cavity. At this age, exogenous feedingstarted and the intestine was differentiated into the an-terior and posterior regions, and the rudimentary liverand pancreas were also seen. Small supranuclear vacu-oles were observed in the enterocytes of the posteriorintestine at 2 dph. Zymogen granules were observed inacinar cells of pancreas by 3 dph, and islets ofLangerhans were visible at 4 dph (3.5 ±0.1 mm SL).At the same age, most of the yolk sac reserves wereconsumed, whereas they were completely exhausted by5 dph (3.9 ± 0.5 mm SL). Between 4 and 6 dph, the liverelongated in size and started to accumulate lipids in thehepatocytes. Gastric glands were detected at 4 dph, andthe pyloric sphincter was completely differentiated at9 dph (6.1 ± 0.4 mm SL) as an epithelial fold thatseparated stomach from the anterior intestine. By13 dph (8.6± 0.2 mm SL), profuse gastric glands werevisible inside longitudinal mucosal folds of the stomach.The formation of gastric glands and their developmentwere noticed as the last events in the development of thedigestive tract in H. fossilis. This indicated the end of thelarval period and the commencement of the juvenilestage. Considering these observations, it is suggestedthat H. fossilis larvae have a morphologically completedigestive tract by 13 dph. The findings of the study onthe development of the digestive system in H. fossilismay help in synchronising the larval stage of develop-ment and feeding strategies and would be helpful inimproving larval rearing techniques for catfish species.Not Availabl