the digestive tract development of snakehead fish channa striata larvae

CAN THO UNIVERSITY COLLEGE OF AQUACULTURE AND FISHERIES THE DIGESTIVE TRACT DEVELOPMENT OF SNAKEHEAD FISH Channa striata LARVAE By TRUONG THI TU NGA A thesis submitted in partial fulfillment of the requirements for the degree of Bachelor of Aquaculture Can Tho, December 2012 CAN THO UNIVERSITY COLLEGE OF AQUACULTURE AND FISHERIES THE DIGESTIVE TRACT DEVELOPMENT OF SNAKEHEAD FISH Channa striata LARVAE By TRUONG THI TU NGA A thesis submitted in partial fulfillment of the requirements for The degree of Bachelor of Aquaculture Supervisor Dr. PHAM THANH LIEM Can Tho, December 2013 Acknowledgements First of all, I wish to express my deep appreciation and sincere gratitude to my supervisor Dr. Pham Thanh Liem for his constant guidance, advice and encouragement in my thesis research and writing. I am gratefully indebted to Mrs. Dang Thuy Mai Thy for her careful guidance in Histological laboratory. I also greatly indebted to Mr. Nguyen Hong Quyet Thang and Nguyen Ngoc Quy for their assistance in the wet laboratory. Many thanks to my classmate in Advanced Aquaculture Class course 35 for their support during my work in the college of Aquaculture and fisheries. Finally, I really want to thank my academic adviser, Dr. Duong Thuy Yen, who was guiding and encouraging me over the last four years, and my family for their great lifetime support which makes everything possible for me. i Abstract The purpose of this study was to observe changes of digestive tract as nutritional characteristics of snakehead fish Channa striata larvae in order to understand feeding behaviour of this species. Development of digestive tract was examined by morphological and histological characteristics. The fish was sampled at day 1, 3, 5, 7, 9, 12, 15, 18, 21, 25, 30 after hatching. For morphological observation, specimen of 10 fishes was sampled to observe the digestive tract under microscope. At the same time, 40 fishes was collected and fixed in buffer formalin 10% or Bouin’s solution to observe the digestive tract by histological method. The morphological result showed that at hatching, development of snakehead larvae exclusively depended on nutrients stored in the yolk. At this time, the digestive tract just was a straight line tube. At day after hatching (DAH) when the fish larvae started exogenous feeding, the digestive tract still was undifferentiated but the zone from which the stomach will be differentiated could be identified. The digestive tract was divided into buccopharynx, esophagus, stomach and intestine distinctly on DAH. The intestine started to coil on day 7. The results of digestive tract development were observed by histological method indicated that the first signs of lipid absorption could be identified as lipid vacuoles in intestine on DAH. The intestine epithelium accumulated of lipid in posterior region from 15 DAH. The gastric gland appeared on day 12, revealing that the stomach became functional. At this time, the digestive tract of this fish was completed in both morphology and histology. ii Table of contents Page Acknowledgements i Abstract ii Table of contents iii List of tables .iv List of figures .v CHAPTER I: INTRODUCTION 1.1 General introduction .1 1.2 Research Objectives .2 1.3 Research Contents Chapter 2: LITERATURE REVIEW .3 2.1 Biology of snakehead 2.2 Status of snakehead culture in Mekong delta 2.3 Histology overview 2.4 Histological studies on fish .6 2.5 General morphology and histology of digestive tract Chapter 3: RESEARCH METHODLODY .12 3.1 Time and place .12 3.2 Materials and methods 12 3.3 Morphological characteristics analysis .13 3.4 Histological method .13 3.5 Result recording .15 Chapter 4: RESULTS AND DISCCUSSION .16 4.1 Morphology development .16 4.2 Histological development .18 Chapter 5: CONCLUSION AND RECOMMENDATION 30 5.1. Conclusion 30 5.2. Recommendation .30 REFERENCES .31 iii List of tables Table 3.1: Chemicals and duration of tissue processing Table 3.2: Chemicals and duration of staining step Table 4.1: Mean total lengths, yolk sac lengths, gut lengths, mouth size and relative gut of lengths (RGL) of Channa striata larvae iv List of figures Figure 2.1: Snakehead fish Channa striata Figure 4.1: DAH larva Figure 4.2: DAH larva Figure 4.3: DAH larva Figure 4.4: DAH larva Figure 4.5: DAH larva Figure 4.6: 12 DAH larva Figure 4.7: 15 DAH larva Figure 4.8: 18 DAH larva Figure 4.9: 21 DAH larva Figure 4.9: 21 DAH larva Figure 4.11: 30 DAH larva Figure 4.12: Longitudinal section of day old snakehead Channa striata larva Figure 4.13: Longitudinal section of buccopharynx of days old larva Figure 4.14: longitudinal section of anterior buccopharynx Figure 4.15: longitudinal section of the esophagus of days old larva Figure 4.16: longitudinal section of the stomach of days old larva Figure 4.17: longitudinal section of 3-day old larva Figure 4.18: Longitudinal section of the stomach of 12 days old larva Figure 4.19: Longitudinal section of the somach og 18 days old larva Figure 4.20: longitudinal section of the stomach Figure 4.21: cross section of stomach Figure 4.22: longitudinal section of the intestine of days old larva Figure 4.23: cross section of the posterior intestine of days old larva Figure 4.24: cross section of intestine of 18 days old larva v vi DT Y Figure 4.12: Longitudinal section of day old snakehead Channa striata larva showing the digestive tract (DT) and yolk sac (Y) (stain: HE, magnification 10x20). When the fish larvae started exogenous feeding, the buccopharynx, esophagus, stomach and intestine was changed as follow: Buccopharynx: The buccopharynx (on DAH) included a thin layer of stratified squamous epithelium which consisted of goblet cells. The thickness of epithelium and the number of goblet cell was increase during larval development stage. 19 B A B A C Figure 4.13: Longitudinal section of buccopharynx of days old larva showing the buccal cavity (A) and the mucosa (B) (stain: HE, magnification 10x20). GC Figure 4.14: Longitudinal section of anterior buccopharynx showing the goblet cells (GC) (stain: HE, magnification 10x40). 20 According to Pham Thanh Liem the buccopharynx of O.marmoratus was composed of a thin layer of stratified squamous epithelium which later consisted of mucous cells and taste bud on DAH. Mai et al. (2010) showed that the Pseudoscianea crocea buccal cavity on DAH was covered with a pseudostratified columnar epithelium surrounded by a thin layer of connective tissue and lamina propria. At this age, few acidophilic goblet cells and basophilic taste buds appeared scattered between the epithelial cells of the buccopharynx. Mucous cells and taste buds were visible throughout the buccopharyngeal epithelium being more abundant in the anterior region of the buccal cavity, while their size and number increased as larvae grew, especially after dph. In Oreochromis niloticus the buccopharyngeal epithelium is composed of a few numbers of squamous cells covered differentiated taste buds; scattered in the anterior and posterior region of the buccal cavity. Mucus-secreting cells are arranged in one layer in the buccopharyngeal epithelium Esophagus The esophagus is a short duct and diferentiated when larvae started exogenous feeding. It was composed of squamous epithelium cell layer. The globlets cells observed on day 7. The folds of mucosa and numbers of goblet cell were increased during larval development. The transition between the esophagus epithelium and the rest of digestive tract were well defined by the absence of goblet cells and single layer of small prismatic epithelial cells of the digestive tract following the esophagus. 21 GC Figure 4.15: longitudinal section of the esophagus of days old larva showing the goblet cells (GC) Infante et al., 2008 stated that at hatching the esophagus of Pseudosciaena crocea larvae is a short and narrow duct lined by a stratified or pseudostratified epithelium, connecting the buccopharyngeal cavity with the anterior opening of the intestine or stomach anlagen Stevens and Hume (2005) found that the epithelium that lines the esophageal mucosa in fish larvae is similar to adults. In general terms, the esophagus of freshwater fish species is lined by a multilayered squamous epithelium with large numbers of goblet cells. According to Pham Thanh Liem, in O.marmoratus species the esophagus differentiated on DAH. It’s contained quamous epithelium cell in the early larval stageand it is started to fold on DAH. However, the oesophagus of Chalcalburnus tarichi pallas was differentiated on the 5th day. The small mucosal folds which consist of a simple cubic epithelium appeared. There were a few goblet cells. On the 5th day, number of goblet cells on esophagus was increased. The circular muscle was observed on the 9th day and the longitudinal muscle in one-year-old fish (Unal, 1999) 22 Stomach The stomach appeared when the fish larvae started exogenous feeding (3DAH). At this age, it could be distinguished at transition between esophagus and intestine with an extended zone (figure 4.16). The mucosa folded and it was composed just of a simple epithelium that was of the columnar type underlain by a thin and loose propria-submucosa (figure 4.15). The stomach was distinguished with intestine by constriction of the digestive tract mucosa. This result was similar to result of histological marble goby O.marmoratus larvae (on day after hatching) that were conducted by Pham Thanh Liem (2001). . Ce Figure 4.16: longitudinal section of the stomach of days old larva showing of columnar epithelium cells (Ce) (stain: HE, magnification: 10x40). 23 A B Figure 4.17: longitudinal section of 3-day old larva (stain: HE, magnification: 10x10) A: stomach, B: intestine. At 12 DAH, the muscular of stomach was thick but only circular muscle blocks were identified in mucuslaris external (figure 4.17) until 18 DAH the stomach of snakehead larvae was made up of four distinct layers: mucosa, lamina propria-submucosa, muscularis and serosa (figure4.18). Similarly, Pham Thanh Liem (2001) found that from day 10-15 in the marble goby O.marmoratus stomach only circular muscle blocks were identified. However, the mucuslaris became twolayer as longitudinal muscles appeared on day 30 after hatching. The muscularis is the thickest layer include of a thin outer longitudinal muscle and a thick inner circular muscle. Observing the stomach section showed that the circular muscle thicker than longitudinal nearly triple The mucosa was composed of tall epithelial cells and blood vessels. The lamina propria contains gastric glands and it made up of loose connective tissue. According to Hybiya (1982), in rainbow trout there are few gastric glands in the cardiac portion but they are numberous in the blind sac and absent in the pyloric portion. 24 C A B Figure 4.18: Longitudinal section of the stomach of 12 days old larva showing the mucosa (A), the mucuslaris (B) and serosa (C) (stain: HE, magnification: 10x10). D C B A Figure 4.19: Longitudinal section of the somach og 18 days old larva (stain: HE, magnification: 10x40) A: mucosa, B: submucosa, C: mucuslaris, D: serosa. 25 The stomach was divided into two parts: a corpus part with a lining of mucous-producing cells with underlying gastric glands and a pyloric part without gastric gland. Gastric glands, which are tubular in shape, are gener-ally situated in the lamina propria and surrounded by a loose connective tissue. The secretory cells present in these glands are responsible for the production of both HCl and pepsinogen, and they are called oxynticopeptic cells. In Channa striata, the gastric glands were appeared on 12 DAH. It revealed that the stomach was completed in digestive function (figure 4.19). After 30 DAH, the gastric glands were observed clearly. GA Figure 4.20: longitudinal section of the stomach showing the gastric glands (GA) (stain: HE, magnifination 10x40). 26 GA Figure 4.21: cross section of stomach showing the gastric glands (GA) Intestine The intestine extends from the end of the pyloric of stomach to the anus. The intestine of Channa striata larvae could be identified on DAH. It consisted of a single layer of columnar epithelial cells which resembled those of stomach layer by thin serosa. The epithelium started to fold on DAH (figure 4.16) and thickness of epithelium cells increased with fish age. At DAH the mucuslaris still was a thin layer of circular smooth muscle (figure 4.19) and the mucosa increased number of fold. At this age, lipid vacuoles were observed (figure 4.21). The lipid vacuoles were accumulated at posterior intestine on day 15. It demonstrated that the posterior region of the intestine is the main site of the digestive tract for lipid absorption (Infante, 2008). At 18 DAH, the intestine also had layers: mucosa, submucosa, mucuslaris and serosa but the mucuslaris layer of intestine was thinner than stomach and the mucosal fold of intestine was narrow (figure 4.22). 27 C A B Figure 4.22: longitudinal section of the intestine of days old larva showing mucosal folds (A), mucuslaris (B), lipid vacuoles (C) (stain: HE, 10x40) L Figure 4.23: cross section of the posterior intestine of days old larva showing lipid vacuoles (L) (stain: HE, magnification 10x20). 28 Figure 4.24: cross section of the intestine of 15 days old larvae (stain: HE, magnification 10x10). B A C D Figure 4.24: cross section of intestine of 18 days old larva (stain: HE, magnification: 10x20) A: mucosa, B: submucosa, C: mucuslaris, D: serosa 29 Delashoub et al. ( 2010) the intestinal wall of big head carp revealed that it is composed of the tunica mucosa, tunica submucosa, tunica muscularis and tunica serosa. It is line by simple columnar epithelium in association with goblet cell, where as the mucosa is thrown into folds (villi). A thin layer of smooth muscle fibers lies between tunica mucosa and submucosa. The tunica muscularis has two layers. Outer layer of intestine is tunica serosa. In the tunica mucosa and submucosa, many eosinophilic granular cells were observed Stroband (1979) stated that the epithelium was a simple columnar one and contained absorbtive enterocytes bear microvilli and cilia, mucus goblet cells and enteroendorine (study on grasscarp). The intestinal epithelium of O.marmoratus larvae had also composed of columnar epithelial cells (1 DAH). The lipid vacuoles were observed on day (Pham Thanh Liem, 2001). 30 Chapter CONCLUSION AND RECOMMENDATION 5.1. Conclusion The digestive tract of newly-hatch larvae just was a straight undifferentiated tube. After DAH when the larvae opened mouth and started exogenous feeding, the esophagus, stomach and intestine can be identified but not distinctly. At DAH, the digestive tract was divided into buccopharynx, esophagus, stomach and intestine; however, the intestine jus was the short line. After 12 DAH, the morphology of digestive tract of larvae was similar to adult fish; the intestine was coiled with V-shape. When the larvae started exogenous feeding, the wall structure of both stomach and intestine was the same. At DAH the lipid vacuoles were observed in posterior intestine as first signs of lipid adsorption. The number of lipd vacuoles in intestine was increased on day 15. The wall thickness of the intestine and stomach was increased with fished age. The stomach of snakehead fish channa striata became functional on day 12. To sum up, at 12 DAH, the digestive tract of snakehead fish Channa striata was completed in both morphology and histology. 5.2. Recommendation Need to have a study to compare development of digestive tract of snakehead Channa striata larvae between different diets to improve fingerling efficiency. 31 REFERENCES Abdulhadi, H.A.A, 2005. Some comparative histological studies on alimentary tract of tilapia fish (Tilapia spilurus) and sea bream (Mylio cuvieri), Egyptian journal of aquatic research ISSN 1110-0354. 31:141-143 Ali, A.B., 1999. Aspect of the reproductive biology of female snakehead (Channa striata, Bloch) obtained from irrigated rice agroecosystem, Malaysia. Hydrobiologia, 411: 71-77. Amornsakun.T, Sriwatana.W and Promkaew.P, 2011. Some aspects in early life stage of snake head fish, Channa striatus larvae. Songklanakarin J. Sci. Technol. 33 (6), 671-677 Arellano, J.M, Storch and C.Sarasquetel, 2001. Histological and histochemical observations in the stomach of the Senegal sole, Solea senegalensis. Histol Histopathol 16: 51 1-521 Bahuguna S. 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Student: Supervisor: 34 [...]... fish survival rates Therefore, some characteristics of morphological and histological changes of digestive tract of fish need to be studied carefully to provide 1 the information that can help improve fingerling quality and commercial production Therefore, the thesis “Study on the digestive tract development of snakehead fish (Channa striata) larvae were conducted to observe changes of digestive tract. .. changes in the digestive tract from newly hatch up to 30 days old 2 Chapter 2: LITERATURE REVIEW 2.1 Biology of snakehead According to Truong Thu Khoa and Tran Thi Thu Huong, 1993, the taxonomy of Channa striata is as following: Class: Actinopterygii Order: Perciformes Family: Channidae Genus: Channa Species: Channa striata Figure 2.1: Snakehead fish Channa striata Snakehead fish Channa striata, Bloch... whereas the cyto-plasm was electron-clear in the other cells Mucus-secreting cells were the dominant feature of the epithelium throughout the oesophagus These gob-let cells were filled with numerous mucous droplets of low electron-density The oesophagus was devoid of taste buds The function of fish s stomach is to break down food so the stomach develops when fish larvae start to feed outside The stomach... started to feed on rotifer when the mouth opening was 0.549 mm (18.70% of mouth opening) at 80 hr after hatching 4.2 Histological development The digestive tract of snakehead Channa striata on 1 DAH just was a straight tube (figure 4.12) lying dorsal to the yolk sac 18 DT Y Figure 4.12: Longitudinal section of 1 day old snakehead Channa striata larva showing the digestive tract (DT) and yolk sac (Y) (stain:... epithelium Esophagus The esophagus is a short duct and diferentiated when larvae started exogenous feeding It was composed of squamous epithelium cell layer The globlets cells observed on day 7 The folds of mucosa and numbers of goblet cell were increased during larval development The transition between the esophagus epithelium and the rest of digestive tract were well defined by the absence of goblet cells... research, the fish larvae opened mouth on 3 DAH but the mouth size just was determined from 5 DAH with the number of 0.759 mm because of sample limiting However, according to Amornsakun et al (2011) the mouth size of Channa striata larvae at 62 hours after hatching was 0.334 mm was similar to that of green catfish, sand goby Green catfish started to feed on Moinawhen the mouth opening was 0.553 mm (40.65% of. .. is eaten through the mouth of the fish using the jaws Most fish have teeth and an immoveable tongue The food then passes through the pharynx (throat) into the esophagus and the stomach Partial digestion 7 takes place in stomach using gastric juices (including acids and enzymes), and then the food proceeds to the intestine for more digestion and absorption into the blood (Huck, 2002) The gut length change... herbivorous) of fish; the gut length of herbivorous fish is higher than the gut length of carnivorous fish However, the digestive tract is not developed as adult fish, Govoni et al (1986) reported that at first feeding, the larval alimentary canal is functional, but is structurally and functionally less complex than that of adults The larval alimentary canal remains unchanged histologically during the larval... histological study of hepatopancreas in hi Fin pangasius (Pangasius sanitwongsei) The results showed that the structure of hepatopancreas in this species was similar to the other fishes However, there were also considerable structural differences 2.5 General morphology and histology of digestive tract Digestion of fish is the process of converting food into smaller compounds that can be used by the body Food... and single layer of small prismatic epithelial cells of the digestive tract following the esophagus 21 GC Figure 4.15: longitudinal section of the esophagus of 7 days old larva showing the goblet cells (GC) Infante et al., 2008 stated that at hatching the esophagus of Pseudosciaena crocea larvae is a short and narrow duct lined by a stratified or pseudostratified epithelium, connecting the buccopharyngeal . Giang, Can Tho, Soc Trang, especially in An Giang province with culture area was 67 ha (occupy 26. 2% of aquaculture aera) and reached 22.273 tons/year of snakehead production (An Giang statistics,