Min-Do Huh

Effects of the different levels of dietary vitamin C on growth and tissue ascorbic acid changes in parrot fish (Oplegnathus fasciatus)

An 11-week feeding trial was conducted to study the effects of the different levels of dietary vitamin C on growth, tissue ascorbic acid concentrations and histopathological changes in parrot fish. Casein and gelatin-based diets were formulated to contain 0, 60, 120, 240, 480 and 2000 mg l-ascorbic acid (AA) per kg diets on AA equivalent basis in the form of l-ascorbyl-2-monophosphate (AMP), 60 and 240 mg AA per kg diet as l-ascorbic acid. However, the analyzed AA levels were 0, 50, 100, 205, 426 and 1869 mg AA per kg diet in AMP supplemented diets; 36 and 149 mg AA per kg diet in l-ascorbic acid supplemented diets. Thus, the diets were designated as AA-free, AMP50, AMP100, AMP205, AMP426, AMP1869, AA36 and AA149. Fish averaging 3.9±0.06 g (mean±S.D.) randomly were fed the experimental diets in triplicate groups for 11 weeks. Weight gain (WG) of fish fed AMP50 and AA36 diets were significantly lower than those of the other groups, and fish fed AMP1869 diet showed a higher WG than did fish fed AMP50, AMP100, AMP205, AA36 and AA149 diets (P<0.05). However, there was no significant difference in WG between fish fed diets AMP426 and AMP1869, and among fish fed AMP100, AMP205, AMP426 and AA149 diets. Fish fed the AA-free diet began to show deficiency signs, such as retarded growth, darkening, anorexia and high mortality, after 3 weeks of feeding trial. After 6 weeks of the feeding trial, liver from fish fed the AA-free diet showed severe atrophy. By the end of the seventh week, all fish fed the AA-free diet were dead. Liver AA concentration from fish fed AMP50 diet was significantly lower than that from fish fed AMP205, AMP426, AMP1869 and AA149 diets, and fish fed AMP50, AMP100, AA36 diets showed a significant lower AA concentration in liver than did fish fed AMP205, AMP426 and AMP1869 diets. Broken line analysis of weight gain indicated that the dietary vitamin C requirement of parrot fish is 118±12 mg AA per kg diet in the form of l-ascorbyl-2-monophosphate for maximum growth.

Histopathological lesions of Manila clam, Tapes philippinarum, from Hadong and Namhae coastal areas of Korea

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.

Characterization of chloramphenicol acetyltransferase gene by multiplex polymerase chain reaction in multidrug-resistant strains isolated from aquatic environments

Abstract Multidrug-resistant isolates carrying the chloramphenicol resistance gene were obtained from aquatic farms in various locations in Korea and studied to determine the distribution and origin of the cat gene. Out of the 134 isolates examined, 10 showed multidrug resistance to several different antibiotics including chloramphenicol (CP). One of these 10 multidrug-resistant bacteria, Vibrio damsela JE1 ( V. damsela JE1) contained a transferable R plasmid encoding CP and tetracycline (TC) resistance genes. The presence of the R plasmid was confirmed by conjugation using the chromocult medium (CC) as a selective and differential medium for transconjugants with identification based on the growth or colors of the colonies. To determine the types of chloramphenicol acetyltransferase genes ( cat ), polymerase chain reaction (PCR) with primers derived from the variable and conserved regions of different types cat genes, appeared to be a very specific and sensitive method. Additionally, we developed the multiplex PCR that allowed us to determine the types of cat genes by the different sizes of the resulting PCR products in a single reaction tube. With the PCR method, we determined that all multidrug-resistant isolates of Vibrio from the farms of the South and East Sea that contained the cat gene carried type IV gene in an R plasmid or other nucleic acids, and the remaining isolates including Edwardsiella tarda , Aeromonas hydrophila and Shewanella sp. carried the type II gene. This result suggested that the type of cat gene in the multidrug-resistant bacteria originated from a very limited environmental or biological source and was not dependent on the location of the area of isolation in Korea.

The Histo-Pathological Change of Rockfish, Sebastes Schlegeli fed the Extruded Pellet and a Raw Fish-based Moist Pellet in Marine Net Cage

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.

Comparative Health Extents of Korean Rockfish, Sebastes Schlegeli by the Commercial extruded Pellet and Moisture Pellet Administration

The purpose of this research is to evaluate the effects of a commercial mixed extruded pellet(EP) and raw fish moist pellet(MP) diet on diseases prevalence and serological constituents and HSI of korean rockfish, Sebastes schlegeli grown in two commercial-scale aquaculture farms from June to December in 2009. The growth of MP-fed rockfish was slightly faster than EP-fed rockfish during experimental period, but did not show significant differences. The levels of TCHO, TG, Glucose and TP in the MP-fed rockfish group were higher than those of EP-fed group, whereas there was no significant difference in other biochemical factors of blood between two groups. In addition, bacteria and virus were not detected in both MP- and EP-fed rockfish groups, and the infection rates of gill fluke between two groups did not show clear difference. In conclusion, there was no comparable difference in growth and the health extents of one year rockfish by administration of the commercial mixed extruded pellet(EP) and raw fish moist pellet(MP) diets.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.