Search

Although over-nutrition from overfeeding-induced obesity is known to be highly associated with metabolic and immunological disorders in humans, little is known about overfeeding-induced obesity in fish farming. The purpose of this study was to investigate changes in immuno-physiological parameters, to better understand the potential risk of overfeeding&ndash, induced obesity in fish. Commercial feed was provided to fish in the overfed group until they refuse to eat, but fish in the control group was fed with the feed at 1% bodyweight per day. The hemato-serological, histological, and immunological changes were observed at weeks 2 and 8. Rainbow trout leukocytes were co-incubated with oxidized low-density lipoprotein (OxLDL), and the phagocytes engulfing the OxLDL and the presence of apoptotic cells were evaluated. The body weight, body mass index (BMI), and hepatosomatic index (HSI) index were significantly higher in the overfed group, and high lipid accumulation and fatty changes were also observed in their livers, indicating that the feeding regime used in this study led to overfeeding-induced obesity. Likewise, much higher numbers of and larger vacuoles were observed in overfed fish macrophages, showing unclear boundaries between the cytoplasm and extracellular space. In the overfed group, the expression of IL-10, HSP70, TLR2, and CD36 was significantly higher, and lymphocyte apoptosis was more evident, indicating that overfeeding-induced obese fish might have immunologic disorders. This was the first study to demonstrate that overfeeding-induced obesity could cause an immune-physiological imbalance in rainbow trout, making them more vulnerable to infectious diseases and various stressful conditions. This study will contribute to improvements in fish nutrition, feeding practices, fish nutrition, and disease prevention in the aquaculture industry.

The monitoring was performed to survey the mortalities and medications occurred in the inland aquaculture farms of olive flounder in South Korea from May to October, 2012. Both of the indirect inquiry for entire inland farms and the sample survey for selected farms were carried out. The aquatic organism disease inspectors, who have the national licenses for the diagnosis and prevention of aquatic organism diseases and have close relationship with the farms, investigated the rates and causes of mortalities according to the standard manual. The cumulative mortalities rate by the indirect inquiry on 565 farms, was calculated to 27.18%, and the mortalities rate by infectious diseases was 22.64%. Otherwise, the mortalities rate by sample survey on 60 farms was 25.50%, 19.33% of them were caused by infectious diseases. The high mortality rates were recorded by scuticociliatosis, non-infectious loss, streptococcosis, VHS, artificial eliminations, vibriosis and gliding bacterial disease. Streptococcosis and non-infectious mortality caused to serious loss in productivity and economy of the farms, because of their outbreaks in the flounder groups over 600 g. The monitoring of medications in the selected farms revealed that formalin for the treatment of external parasites, such as scuticociliates, was the most commonly used drugs in the farms. As the antibiotic medications, amoxicillin and florfenicol for streptococcosis, and oxytetracycline and neomycin expecting wide antibacterial spectrum, were frequently prescribed.

In this study, 6-10 clinically healthy farmed abalone, Haliotis discus hannai were obtained from Jeollanam-Do Wando Soan-myeon, Bogil-myeon, and Nohwa-eup monthly for 1 year 7 months and were examined histopathologically. As a result, the adductor muscle had severe cellular swelling and myonecrosis. These lesions were stained with hematoxylin and eosin and Giemsa. The lesions were not caused by infection of bacteria or parasites. We investigated the relationship between lesion frequency and water temperature and discovered that increased water temperature was associated with increasing lesion frequency. As water temperature is related to growth rate, increased growth rate was closely related to increased lesion frequency. We considered that these lesions could be a useful factor in measuring shellfish health.

A histo-pathogical examination was carried out to evaluate the effect of commercial extruded pellet (EP) and a raw fish moist pellet (MP) diet on the health of juvenile rockfish cultured in marine net-cage for 7 months. Fish were distributed randomly to each net cage as a group of 76,000 fish (initial mean body weight 5.9 g). After 2 months, the hypertrophy or swelling of liver parenchymal cells was identified in most individuals and lasted until 7 months. Livers in EP fed group frequently showed hypertrophic parenchyma and fatty change with occasional atrophic cells. However, after 4 months, lymphocytic infiltration in splenic parenchyma was seen in a number of individuals. In addition, the gastric glandular epithelium was atrophied and in the lumen of renal tubules protozoan parasites were frequently identified but there was no correlation with the type of feed. Moreover, juvenile rockfish on EP diet showed gross and microscopic hypertrophy of the liver which would be due to oversupply of feed. Severe hepatic cellular hypertrophy or swelling could lead to the damage of microcirculation. Especially fatty change and atrophic change of liver could be the result from the damage, which could be responsible for immunological problem. Lymphocytic infiltration of spleen on the MP diet suggests that juvenile rockfish could be frequently exposed to infectious antigens.

This study was aimed to determine the fish physical status according to the gross and histopathological findings of liver in cultured black rock fish, Sebastes schlegeli. All 47 fish submitted had no marked abnormalities in the external findings. 42.55% of fish showed normal liver, 25.53% yellow liver, 25.53% atrophic brown liver, 4.26% yellowish-green liver and 2.13% fatty liver in gross examination. Grossly normal liver showed no remarkable change in lobular structure but many vacuoles were found in hepatic cell. Hepatic cells took normal roundish, polygonal shapes containing spherical nuclei. In group of yellow-brown liver, many brown pigments were seen in hepatic cells, MMCs and brown-colored hyaline droplets within cytoplasm of hepatocytes. Yellowish green pigments were seen in hepatic cells and MMCs of yellow green liver and green colored hyaline droplets within hepatocytes. The dilated central veins are highlighted with atrophy of hepatic cells. Outline of atrophic hepatocyte became ambiguous and nucleus frequently become small and pyknotic. Fatty liver showed prominent vacuolar structures in cells as clear spaces or foamy cytoplasm with degenerative nuclei. From these results, it was strongly suggested that hepatic gross and histological findings could be used as important and critical health parameters of fish prior to progression to substantial manifestation as clinical disease.

This study was aimed to investigate the pathophysiological changes of olive flounder, Paralichthys olivaceus suffering from emaciation. A plasma osmolality was higher in the emaciated and control flounders than that of normal teleost, suggesting osmoregulatory failure in both of them. Also, the control in the same stock with emaciated flounder seem to be classified into a primary degree of emaciation. According to microscopic observations, the inflammatory responses were observed in the submucosal layer of anterior intestine, although the some of mucosal intestinal epithelium still remained. It was suggested that the pathological changes of the anterior part give rise to malabsorption of nutrients through the mucosa. In the posterior intestine and rectum, the mucosal epithelium were almostly sloughed off and severe inflammatory responses were observed in the submucosa. Immunoreaction for NKCC was not detected in the mucosal epithelial cells in intestine because of sloughing of epithelium. These changes would lead to functional disorder in the intestine, such as malabsorption of nutrients and osmoregulatory failure. Also important is to investigate the recovery phase.

In order to determine a causal relation between infections and death of Manila clam, Tapes philippinarum, a routine histopathological survey was carried out along the southern coast of Korea from March 1996 to April 1997. Three kinds of parasites (Perkinsus sp., Marteilioides-like organism and Cercaria tapidis) were encountered frequently. The latter two parasites infected the gonad but did not evoke any significant host reaction. However, Perkinsus sp. infestation was characterized by a variable degree of hemocytic encapsulation. Digestive epithelia including those in the digestive diverticula showed various degrees of atrophic changes. Hemocytic infiltration occurred in various tissues and organs also to a variable degree. From the point of view of frequency as well as pathological impact, it was strongly suggested that the atrophy of digestive epithelium, hemocytic encapsulation associated with Perkinsus sp., hemocytic infiltration in various tissues and organs are lesions that should be carefully monitored for association with bivalve mortality.