Viswanath Kiron

Trace minerals in fish nutrition

Abstract The role of trace elements in biological systems has been described in several animals. However, the knowledge in fish is mainly limited to iron, copper, manganese, zinc and selenium as components of body fluids, cofactors in enzymatic reactions, structural units of non-enzymatic macromolecules, etc. Investigations in fish are comparatively complicated as both dietary intake and waterborne mineral uptake have to be considered in determining the mineral budgets. The importance of trace minerals as essential ingredients in diets, although in small quantities, is also evident in fish.

Prospects in larval fish dietetics

Abstract Larviculture today depends principally on live food. Artificial micro-feeds are gradually gaining acceptance in the industry. A wholesome prepared food for the larvae is still unknown to science. Advances in biology and technology seek to break one of the last hurdles in the aquaculture cycle.

Teleost intestinal immunology.

Teleosts clearly have a more diffuse gut associated lymphoid system, which is morphological and functional clearly different from the mammalian GALT. All immune cells necessary for a local immune response are abundantly present in the gut mucosa of the species studied and local immune responses can be monitored after intestinal immunization. Fish do not produce IgA, but a special mucosal IgM isotype seems to be secreted and may (partly) be the recently described IgZ/IgT. Fish produce a pIgR in their mucosal tissues but it is smaller (2 ILD) than the 4-5 ILD pIgR of higher vertebrates. Whether teleost pIgR is transcytosed and cleaved off in the same way needs further investigation, especially because a secretory component (SC) is only reported in one species. Teleosts also have high numbers of IEL, most of them are CD3-ɛ+/CD8-α+ and have cytotoxic and/or regulatory function. Possibly many of these cells are TCRγδ cells and they may be involved in the oral tolerance induction observed in fish. Innate immune cells can be observed in the teleost gut from first feeding onwards, but B cells appear much later in mucosal compartments compared to systemic sites. Conspicuous is the very early presence of putative T cells or their precursors in the fish gut, which together with the rag-1 expression of intestinal lymphoid cells may be an indication for an extra-thymic development of certain T cells. Teleosts can develop enteritis in their antigen transporting second gut segment and epithelial cells, IEL and eosinophils/basophils seem to play a crucial role in this intestinal inflammation model. Teleost intestine can be exploited for oral vaccination strategies and probiotic immune stimulation. A variety of encapsulation methods, to protect vaccines against degradation in the foregut, are reported with promising results but in most cases they appear not to be cost effective yet. Microbiota in fish are clearly different from terrestrial animals. In the past decade a fast increasing number of papers is dedicated to the oral administration of a variety of probiotics that can have a strong health beneficial effect, but much more attention has to be paid to the immune mechanisms behind these effects. The recent development of gnotobiotic fish models may be very helpful to study the immune effects of microbiota and probiotics in teleosts.

Nonspecific immune response of rainbow trout (Oncorhynchus mykiss Walbaum) in relation to different status of vitamin E and highly unsaturated fatty acids

This study was designed to examine the effects of dietary vitamin E (VE) on modulation of immune responses when supplied with two levels of n-3 highly unsaturated fatty acids (n-3 HUFA) in rainbow trout, Oncorhynchus mykiss. Six semipurified diets were prepared containing three levels of dietary VE (0, 100 or 1000 mg alpha-tocopheryl acetate kg(-1) diet) and n-3 HUFA either at 20 or 48% of dietary lipid provided from fish oil or docosahexaenoic acid (DHA) concentrated fish oil respectively. The diets were fed to rainbow trout (100 g initial mean weight) for 15 weeks. The VE, vitamin C (VC) content in plasma and tissues and the nonspecific immune responses, both humoral (alternative complement activity, total immunoglobulin) and cellular (phagocytosis, nonspecific cytotoxicity) were examined. VE contents in the kidney reflected the dietary input but were lower in fish fed 48% n-3 HUFA diets, and could have impaired some of immune responses compared to fish fed 20% n-3 HUFA. VC contents in kidney followed the same pattern as VE. Both humoral and cellular immune functions deteriorated in fish fed VE deficient diets whereas improvement in most of the parameters corresponded to its supplementation. However, the higher dose of dietary VE did not substantially enhance the responses assayed compared to the 100 mg dose. Besides clearly indicating the role of VE in maintaining the immune functions in fish in relation to dietary n-3 HUFA, this study has revealed that optimum health benefits could be achieved when VE is maintained slightly above the levels generally recommended for normal growth.

Common Carp, Cyprinus carpio

The common carp (Cyprinus carpio) belongs to the family Cyprinidae. In nature, carp live in the middle or lower reaches of a river with slow currents, or in marshes. Their habitats are usually weedy areas with a muddy bottom. Carp fry feed on zooplankton such as rotifers and copepods, but as they grow up they become benthic feeders, feeding on animals and other organic material. The cyprinids have been farmed since ancient times and today they are undoubtedly the most important teleost family cultivated on a global scale, the current production figure reaching over 13 million tons year−1. The common carp is an important culture species among the cyprinids, next only to silver carp and grass carp (Fig. 18.1), and its production has doubled over the last decade, reaching about 2.5 million tons in 1998, valued at US

Essential fatty acid nutrition and defence mechanisms in rainbow trout Oncorhynchus mykiss

2.8 billion (Fig. 18.2). A large percentage of this is from the Asian region, particularly China. While production of common carp is widely practised, only about 3% of the cyprinids are cultivated in intensive systems (Tacon, 1993). Traditionally, carp are cultured in ponds or rice paddies, while advanced culture systems include irrigation ponds, running-water systems and net cages in lakes. The more organized culture techniques involve maintenance of breeders, fry production, yearling production and marketable fish production. The operations and feeding practices are outlined in Table 18.1. Relatively low-cost prepared diets are in vogue and little effort has been made to supply adequate amounts of nutrients from carefully selected ingredients, despite the existence of a great deal of scientific information.

Adaptive immune responses at mucosal surfaces of teleost fish.

The influence of saturated and polyunsaturated fatty acids on immune responses of rainbow trout was investigated. In vitro killing of bacteria by macrophages and antibody production were compromised by dietary essential fatty acid deficiency in fish. Polyunsaturated fatty acids fed fish were stronger in resisting pathogens, but excess levels of n-3 highly unsaturated fatty acids may not be effective. Essential fatty acids enhance immunocompetence.

Intraperitoneal vaccination of Atlantic cod, Gadus morhua with heat-killed Listonella anguillarum enhances serum antibacterial activity and expression of immune response genes.

This review describes the extant knowledge on the teleostean mucosal adaptive immune mechanisms, which is relevant for the development of oral or mucosal vaccines. In the last decade, a number of studies have shed light on the presence of new key components of mucosal immunity: a distinct immunoglobulin class (IgT or IgZ) and the polymeric Ig receptor (pIgR). In addition, intestinal T cells and their putative functions, antigen uptake mechanisms at mucosal surfaces and new mucosal vaccination strategies have been reported. New information on pIgR of Atlantic cod and common carp and comparison of natural and specific cell-mediated cytotoxicity in the gut of common carp and European seabass, is also included in this review. Based on the known facts about intestinal immunology and mucosal vaccination, suggestions are made for the advancement of fish vaccines.

Proteome reference map of the skin mucus of Atlantic cod (Gadus morhua) revealing immune competent molecules

Serum-mediated reduction in bacterial count and expression of a number of immune response genes in the blood of Atlantic cod, Gadus morhua were investigated following intraperitoneal vaccination with heat-killed Listonella (Vibrio) anguillarum. Blood was collected from the caudal vein of both vaccinated and non-vaccinated (PBS-injected) fish at 0, 1, 3, 7 and 10 days post-vaccination (dpv). Serum protein concentration and antibacterial activity of the serum samples were determined. Whole blood was used for semi-quantitative RT-PCR of immune-related genes. Total serum protein was not significantly different between the vaccinated and non-vaccinated groups. Sera from the vaccinated fish significantly reduced L. anguillarum count on 3 dpv, with reductions of at least 2 log colony forming units per ml (CFU/ml) relative to the non-vaccinated fish. Expression of antibacterial genes, bactericidal/permeability-increasing protein/lipopolysaccharide-binding protein (BPI/LBP), g-type lysozyme and transferrin was significantly upregulated in the vaccinated fish, with maximum expression within 7 dpv. Cytotoxic-related and cell-mediated immunity genes such as, apolipoprotein A-I and the non-specific cytotoxic cell receptor protein (NCCRP-1) had maximum expression at 3 and 7 dpv, respectively. Significant upregulation in expression of pro-inflammatory cytokines, IL-1 beta and IL-8 was also observed in the vaccinated fish at 1 dpv. The upregulation of immune response genes following vaccination provides valuable information in the understanding of immune mechanisms against vibriosis in Atlantic cod particularly on the acute phase response during bacterial infection.

Comparison of phosphorus retention efficiency between rainbow trout (Oncorhynchus mykiss) fed a commercial diet and a low fish meal based diet

The skin mucosal proteome of Atlantic cod (Gadus morhua) was mapped using a 2D PAGE, LC-MS/MS coupled approach. Mucosal proteins from naive fish were identified primarily by similarity searches across various cod EST databases. The identified proteins were clustered into 8 groups based on gene ontology classification for biological process. Most of the proteins identified from the gel are hitherto unreported for cod. Galectin-1, mannan binding lectin (MBL), serpins, cystatin B, cyclophilin A, FK-506 binding protein, proteasome subunits (alpha-3 and -7), ubiquitin, and g-type lysozyme are considered immune competent molecules. Five of the aforementioned proteins were cloned and their tissue distribution was analysed by RT-PCR.