Shieh-Tsung Chiu

The increase of immunity and disease resistance of the giant freshwater prawn, Macrobrachium rosenbergii by feeding with selenium enriched-diet.

The effects of inorganic selenium (Se) (sodium selenate, SSe) and organic selenium (seleno-l-methionine, MSe) supplementation on the immune response, antioxidant status, and disease resistance of the giant freshwater prawn, Macrobrachium rosenbergii, were studied. Five experimental diets, including a control diet (without Se enrichment), 0.5 mg (kg diet)(-1) of MSe, 1 mg (kg diet)(-1) of MSe, 0.5 mg (kg diet)(-1) of SSe, and 1 mg (kg diet)(-1) of SSe, were used. After 75 days of culture, prawn fed the Se-enriched diets had lower mortality compared to that of prawn fed the control diet after being challenged by the pathogen, Debaryomyces hansenii. No significant differences in the total hemocyte count, superoxide dismutase activity, or clearance efficiency of prawn were recorded among the control and treated groups. Significantly increased phenoloxidase and phagocytic activities in prawn fed the Se-enriched diets were found compared to the controls. Respiratory bursts of prawn fed both forms of 1 mg Se (kg diet)(-1) significantly increased compared to control prawns. For the antioxidant status analysis, glutathione peroxidase, glutathione reductase, and glutathione s-transferase of prawn fed the SSe-enriched diet at 1 mg (kg diet)(-1) were significantly increased. The results indicated that the cheaper selenium, SSe is recommended to be added in prawn feed at the concentration of 0.5 mg resulting in 1.5 mg SSe (kg diet)(-1) increased prawn immunity and disease resistance against the pathogen, D. hansenii.

Improvement in non-specific immunity and disease resistance of barramundi, Lates calcarifer (Bloch), by diets containing Daphnia similis meal.

A 42-day study was conducted with barramundi, Lates calcarifer, to evaluate the effects of Daphnia meal derived from Daphnia similis on fish growth, immune response, and disease resistance to Aeromonas hydrophila. Three isonitrogenous (45%) and isolipid (10%) experimental diets were formulated to contain 0% (control), 5% (D5), and 10% (D10) Daphnia meal. Growth was depressed when fish were fed with the D10 diet for 42 days compared to control. However, the growth in fish fed with control and D5 diets for 42 days was not significantly different. By day 42, the leukocyte phagocytic activity and respiratory burst activity were significantly increased in D5 and D10 groups compared to control. Mx gene expression in the spleen and head kidney of fish after being injected with nerve necrosis virus was also significantly up-regulated in both groups compared to control. In an increased immune response, D5 and D10 fish had significantly higher survival rates than control after being challenged by A. hydrophila. Therefore, we suggest that a 5% Daphnia-meal diet could improve the barramundi immune response and disease resistance without a negative impact on growth.

The Influence of Epistylis sp. on Osmotic, Ionic, and Respiratory Physiology of the Giant Freshwater Prawn, "Macrobrachium rosenbergii" in the Terminal-growth Stage

Differences in osmolality, ion concentrations, and respiratory metabolism of the hemolymph were investigated in terminal-growth male and other morphotypes of healthy prawn, including males of orangeclaw and blue-claw, and females of the giant freshwater prawn, Macrobrachium rosenbergii. In addition, gill-injured prawns were also used to analyze those same parameters in this study. No significant differences in hemolymph osmolality, ion levels, or respiratory metabolism among blue-claw males, orange-claw males, and females were found. Hemolymph osmolality, chloride, potassium, sodium, calcium, and magnesium concentrations in terminal-growth males were significant lower than in other types of prawn. Significantly lower oxyhemocyanin and protein, and significantly higher hemolymph pH and PCO2 in terminal-growth males were found compared to other types of prawn. Insignificant differences in the ratio of oxyhemocyanin and protein, and in hemolymph PO2 among terminal-growth males and other types of prawn were recorded. Histopathological lesions in gills of terminal-growth males caused by an Epistylis sp. infestation and impurities covering the gills were found, that may have involved interference with gas exchange, hemolymph osmolality, and ion regulation. Prawns with partially injured gills had significantly decreased regulation of osmolality and ions in the hemolymph, but no significant change in respiratory metabolism compared to control prawn. Prawn gills are considered the main tissuefor hemolymph osmolality and ion regulation because hemolymph osmolality and ion levels of prawn decreased when gills of prawn were partially injured. However, respiratory metabolism was compensated for by normal gills in prawns with partially injured gills. The information obtained from this study adds to knowledge of prawn pathophysiology and may give a clearer profile of changes in hemolymph osmolality, ion concentrations, and respiratory metabolism caused by gill injury.