Influence of Selected Dietary Micronutrient Elements on Growth and Biochemistry of Farmed Prawns

From the present study, it is clear that all the three metals, selenium, molybdenum and cobalt have significant effect on the antioxidant status of the shrimps. Selenium and molybdenum were observed to induce peroxidative damage at elevated levels. But at the same level, cobalt did not show such an effect. Selenium was found to be growth promoting at lower levels of dietary supplementation. Even though low levels of dietary selenium had a protective effect against the lipid peroxidation, the present study indicates that high levels of dietary selenium could promote lipid peroxidation. The selenium-dependent antioxidant enzyme, GPx behaved differently in muscle and hepatopancreas. A high concentration of selenium was required for the active expression of the enzyme in the muscle, where as in hepatopancreas maximum activity was observed at lower selenium concentration. Selenium supplementation had a positive effect on GSH concentration. The other antioxidant enzymes such as GST, SOD and CAT showed enhanced activity at higher concentration of selenium. Molybdenum supplementation significantly reduced the free radical scavenger enzymes SOD and CAT. This resulted in enhanced lipid peroxidation in tissues. The activity of antioxidant enzyme GPx and the concentration of the substrate for the enzyme, GSH also were lower at elevated levels of molybdenum supplementation. In addition to this amino acids and fatty acids were also altered in molybdenum supplemented groups. In trace amounts, dietary molybdenum exerts a beneficial effect on the growth and also in the activities of the enzymes XO and SO. At the same time it also indicates a possibility of oxidative damage as a result of the peroxidation caused by the activities of the enzymes SO and XO at elevated concentrations of molybdenum is also indicated. The absorption of various trace elements was also altered by molybdenum supplementation.Among the three metals studied, cobalt was the least toxic one at the administered levels. But this metal has a significant effect on the lipid content, amino acid composition, cholesterol levels and phospholipid levels. Increased growth was also observed as a result of cobalt supplementation in shrimps. The antioxidant system of the animal was activated by dietary cobalt. Tissue levels of the trace metals were also found to be altered in cobalt supplemented groups of shrimps.These studies, thus shows that influence of dietary trace metals calls for more detailed studies in farmed shrimp. They may hold the key to growth and even disease resistance in shrimp. But this still remains as a virgin field which demands more attention, especially in view of the increasing importance of shrimp farming.

Penaeus monodon larvae can be protected from Vibrio harveyi infection by pre-emptive treatment of a rearing system with antagonistic or non-antagonistic bacterial probiotics

This study shows that the disease resistance and survival rate of Penaeus monodon in a larval rearing systems can be enhanced by supplementing with antagonistic or non-antagonistic probiotics. The antagonistic mode of action of Pseudomonas MCCB 102 and MCCB 103 against vibrios was demonstrated in larval mesocosm with cultures having su⁄cient concentration of antagonistic compounds in their culture supernatant. Investigations on the antagonistic properties of Bacillus MCCB 101, Pseudomonas MCCB 102 and MCCB 103 and Arthrobacter MCCB 104 against Vibrio harveyi MCCB111under in vitro conditions revealed that Pseudomonas MCCB 102 and MCCB 103 were inhibitory to the pathogen.These inhibitory propertieswere further con¢rmed in the larval rearing systems of P. monodon. All these four probionts signi¢cantly improved larval survival in long-term treatments as well as when challengedwith a pathogenic strain ofV. harveyiMCCB111. We could demonstrate that Pseudomonas MCCB 102 andMCCB103 accorded disease resistance and a higher survival rate in P. monodon larval rearing systems throughactive antagonism of vibrios,whereas Bacillus MCCB 101 and Arthrobacter MCCB 104 functioned as probiotics through immunostimulatory and digestive enzyme-supporting modes of action.

Molecular genetic profiling of functional genes of pearl oyster, Pinctada fucata

There are a number of genes involved in the regulation of functional process in marine bivalves. In the case of pearl oyster, some of these genes have major role in the immune/defence function and biomineralization process involved in the pearl formation in them. As secondary filter feeders, pearl oysters are exposed to various kinds of stressors like bacteria, viruses, pesticides, industrial wastes, toxic metals and petroleum derivatives, making susceptible to diseases. Environmental changes and ambient stress also affect non-specific immunity, making the organisms vulnerable to infections. These stressors can trigger various cellular responses in the animals in their efforts to counteract the ill effects of the stress on them. These include the expression of defence related genes which encode factors such as antioxidant genes, pattern recognition receptor proteins etc. One of the strategies to combat these problems is to get insight into the disease resistance genes, and use them for disease control and health management. Similarly, although it is known that formation of pearl in molluscs is mediated by specialized proteins which are in turn regulated by specific genes encoding them, there is a paucity of sufficient information on these genes.In view of the above facts, studies on the defence related and pearl forming genes of the pearl oyster assumes importance from the point of view of both sustainable fishery management and aquaculture. At present, there is total lack of sufficient knowledge on the functional genes and their expressions in the Indian pearl oyster Pinctada fucata. Hence this work was taken up to identify and characterize the defence related and pearl forming genes, and study their expression through molecular means, in the Indian pearl oyster Pinctada fucata which are economically important for aquaculture at the southeast coast of India. The present study has successfully carried out the molecular identification, characterization and expression analysis of defence related antioxidant enzyme genes and pattern recognition proteins genes which play vital role in the defence against biotic and abiotic stressors. Antioxidant enzyme genes viz., Cu/Zn superoxide dismutase (Cu/Zn SOD), glutathione peroxidise (GPX) and glutathione-S-transferase (GST) were studied. Concerted approaches using the various molecular tools like polymerase chain reaction (PCR), random amplification of cDNA ends (RACE), molecular cloning and sequencing have resulted in the identification and characterization of full length sequences (924 bp) of the Cu/Zn SOD, most important antioxidant enzyme gene. BLAST search in NCBI confirmed the identity of the gene as Cu/Zn SOD. The presence of the characteristic amino acid sequences such as copper/zinc binding residues, family signature sequences and signal peptides were found out. Multiple sequence alignment comparison and phylogenetic analysis of the nucleotide and amino acid sequences using bioinformatics tools like BioEdit,MEGA etc revealed that the sequences were found to contain regions of diversity as well as homogeneity. Close evolutionary relationship between P. fucata and other aquatic invertebrates was revealed from the phylogenetic tree constructed using SOD amino acid sequence of P. fucata and other invertebrates as well as vertebrates