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Histopathological Health Assessment of Farmed Olive Flounder Paralicthyes Olivaceus

M M Rashid
Department of Fisheries, Matshya Bhaban, 1000 Dhaka, Bangladesh; The Graduate School, Pukyong National University, Busan, South Korea

M M M Alam*
Department of Fish Health Management, Sylhet Agricultural University, 3100 Sylhet, Bangladesh

M D Huh
The Graduate School, Pukyong National University, Busan, South Korea

M M Rahman
Department of Fish Health Management, Sylhet Agricultural University, 3100 Sylhet, Bangladesh

Abstract/ Executive Summary:

A histopathological health assessment for olive flounder Paralicthyes olivaceus, with different size based on total body length and weight, was carried out. Two samplings were performed: (I) on 4th October 2010 and (II) on 25th January 2011. Two groups of fishes were administered for the study from the same culture system and age group- the big sized fishes (fast growing) and the small sized fishes (slow growing). Clinical record, blood chemistry, total protein (Tp), hemoglobin (Hb), hematocrit (Ht), functional indices i.e., hepato somatic index (HSI) and hepato hypertropic index (HHI), and histological studies of different organs (liver, stomach, intestine, spleen, kidney and heart) were performed for each individual of each group. Moderate to severe fatty change of liver were observed in both groups of fishes in case of sampling I. Moderate to severe atrophy of liver were observed in both groups of sampling II. Focal epicarditis were observed in sampling I for big sized fishes, and vacuolative changes of gastric gland of big sized fishes were observed in sampling II under light microscopic examination. Tp, Ht, and HHI were recorded significantly higher (p values ranged from 0.001 to 0.032) for big sized fish group in sampling I. In sampling II only HHI was found significantly higher (p = 0.004) in big sized fish group. Thus, it can be concluded that fast growing individuals are more vulnerable to disease based on the histopathological assessment. This information will be helpful to prevent and control diseases for different age groups of olive flounder by taking different management practices.

Keywords: Fatty change, Epicarditis, Vacuolative change, Olive flounder, Paralichthyes olivaceus.

Location: Department of Fisheries, Matshya Bhaban, 1000 Dhaka, Bangladesh

Start Date: 04-10-2010

End Date: 25-01-2011

Program Area: Risk Management in Agriculture

Commodity: Olive

Objectives:

The aim of the present study was to investigate histopathological health status of olive flounder of the same age and culture system with different sized fishes in terms of total length and body weight to know the susceptibility and intensity of infection for proper health management.

Methodology:

Two categories of fishes were chosen from same age group and culture system according to their body weight and total length, considering the intensity of infection may differ for age groups and culture systems. Six big sized fish group (fast growing) with the average length of 27.58 cm and 26.70 cm and the average weight of 221.83 g and 404.00 g at sampling I and II, respectively. Six small sized fish group (slow growing) with the average length of 22.58 cm and 22.03 cm and the average weight of 125.83 g and 215.00 g at sampling I and II, respectively were utilized. Six fishes were selected in each group for more accuracy. Liver and stomach were taken as focus organ for the study. Other organ such as, intestine, spleen, heart, body kidney, gill and functional indices i.e. total protein (Tp), hemoglobin (Hb), hematocrit (Ht), hepato somatic index (HSI) and hepato hypertropic index (HHI), were also taken in consideration for clear clarification. To pursue the experiment and processing of tissue for Histopathological study, the following chronological steps were followed. Sample collection: Fishes were collected from a local fish farm named Dongji fish farm, Gijang in Busan and subsequently carried to the laboratory in polyethylene bag with oxygen in live condition. Samplings were done two times. First one (sampling I) was on 4th October 2010 and the second one (Sampling II) was on 25th January 2011. History taking: General history regarding culture system, feeding, stocking density and other information were also collected from the farm operators. Clinical record and blood chemistry: By examining each individual’s clinical information were recorded. Blood chemical parameters such as total protein, haematocrit and hemoglobin were also taken after collecting blood from caudal vein. Dissecting of the fish: Operculum and body cavity were opened by dissecting fishes with sharp scissors and forceps. Photos of the internal organ of each individual were taken with a digital camera system (OLYMPUS E-P2, Japan). Fixation and refixation: Subsequently after dissection, samples were fixed in Bouin’s solution. After 24 hours of fixation samples were cut into suitable pieces with sharp blade and put in labeled cassettes (Categorized as organ and individuals). Then these samples were refixed in 10% buffered formalin solution. Tissue processing: All fixed tissues were passed through a series of solvents before finally being embedded fully with paraffin wax. In the present study tissues were washed and dehydrated through alcoholic grades (70%, 80%, 90%, 95%, 100%, 100% and 100%) and cleaned in xylene. Embedding: Tissues were embedded with paraffin wax at 58– 62^oC. Sectioning: Embedded blocks were cut at 5 micron in thickness by rotatory type microtome (Reichert-jung820, Leica LTD). The sectioned ribbon was floated on warm water bath (54^oC) to flatten out the section. The sections were carefully collected on to a glass slide, allowed to dry fully before proceeding to H&E staining. Staining: Hematoxylin and eosin (H&E) staining methods were followed to stain the prepared slides. Mounting: The stained samples were mounted with Canada balsam for permanent preservation. Photography: Photos of the prepared slides of different organ were taken, using the software DP2-BSW (Olympus, Japan). Calculation of HHI: HHI, hepatohypertrophic index was calculated using the image analyzer (Image pro-plus3, Media cybernetics). At first the number of nucleus in 1,000 µm² were counted, using the software and then values were put in the following formula and HHI were calculated. HHI= 1/Log (Number of nucleus count in 1,000µm² )

Source of Information: J. Sylhet Agril. Univ. 2(2):257-266, 2015 ISSN: 2308-1597

Article Link (Online Journal):

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

To conclude, a clear histopathological difference between big and small sized fish group were observed in case of stomach with vacuolative changes in gastric gland in big sized fish group for sampling II. HHI values were also found significantly higher (p < 0.01) in big sized fish groups in both samplings. Some significant higher (p values ranged from 0.001 to 0.032) values were also observed for Tp and Ht in sampling I for big sized fish group. Vacuolative changes in gastric gland for big sized fishes are an important observation for the present study. Vacuolative changes in gastric gland may lead to critical pathological state and could have contributed to increase mortality. Vacuolative changes and atrophy of gastric gland related to the higher feeding regime. High feeding regime causes hyper secretory activities of gastric glands and leading to vacuolative change and atrophy of gastric glands. Overfeeding, leading to dysfunction of liver by mechanically obliterating the microcirculation of hepatic parenchyma. The visceral organs are important component of the defense system (Fange, 1984). Higher HHI values in big sized fishes implicated over nourished state. Severe increase of HHI values obliterate the Disse space and sinusoids which lead to hypertrophy, fatty change, atrophy and necrosis of liver. Finally it may lower the immunity of fish and cause more vulnerable to disease. The present study is only based on fish size from same age group and culture system. Impacts of different feeding regimes are also important for health assessment of fishes. Further studies with different feeding regimes and their relationship to fish’s susceptibility to disease are required.

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