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Experimental studies were conducted by injecting or feeding white spot syndrome virus (WSSV) derived from infected shrimp, Penaeus monodon (Fabricius), collected from the south‐east coast of India, to five species of shrimp, two species of freshwater prawns, four species of crabs and three species of lobsters. All species examined were susceptible to the virus. Experimental infections in the shrimp had the same clinical symptoms and histopathological characteristics as in naturally infected P. monodon. A cumulative mortality of 100% was observed within 5–7 days in shrimp injected with WSSV and 7–9 days in shrimp fed with infected tissue. Two species of mud crab, Scylla sp., survived the infection for 30 days without any clinical symptoms. All three species of lobsters, Panulirus sp., and the freshwater prawn, Macrobrachium rosenbergii (De Man), survived the infection for 70 days without clinical symptoms. However, bioassay and histology using healthy P. monodon revealed that crabs, prawns and lobsters may act as asymptomatic carriers/reservoir hosts of WSSV. This is the first report to suggest the carrier/reservoir capacity of these hosts through histological and bioassay evidences. Ultrastructural details of the virus in experimentally infected shrimp, P. vannamei, (Boone), were also studied.

A Pseudomonas sp PS-102 recovered from Muttukkadu brackish water lagoon, situated south of Chennai, showed significant activity against a number of shrimp pathogenic vibrios. Out of the 112 isolates of bacterial pathogens comprising Vibrio harveyi, V. vulnificus, V. parahaemolyticus, V. alginolyticus, V. fluvialis, and Aeromonas spp, 73% were inhibited in vitro by the cell-free culture supernatant of Pseudomonas sp PS-102 isolate. The organism produced yellowish fluorescent pigment on King's B medium, hydrolysed starch and protein, and produced 36.4% siderophore units by CAS assay and 32 μM of catechol siderophores as estimated by Arnow's assay. The PS-102 isolate showed wide ranging environmental tolerance with, temperatures from 25 to 40°C, pH from 6 to 8, salinity from 0 to 36 ppt, while the antagonistic activity peaked in cultures grown at 30°C, pH 8.0 and at 5 ppt saline conditions. The antagonistic activity of the culture supernatant was evident even at 30% v / v dilution against V. harveyi. The preliminary studies on the nature of the antibacterial action indicated that the antagonistic principle as heat stable and resistant to proteolytic, lipolytic and amylolytic enzymes. Pseudomonas sp PS 102 was found to be safe to shrimp when PL-9 stage were challenged at 10 7 CFU ml − 1 and by intramuscular injection into of ∼5 g sub-adults shrimp at 10 5 to 10 8 CFU. Further, its safety in a mammalian system, tested by its pathogenicity to mice, was also determined and its LD 50 to BALB/c mice was found to be 10 9 CFU. The results of this study indicated that the organism Pseudomonas sp PS 102 could be employed as a potential probiont in shrimp and prawn aquaculture systems for management and control of bacterial infections.

A rapid and convenient procedure has been developed for the measurement of mRNA half-life in S.cerevisiae using the transcriptional inhibitor, 1,10-phenanthroline. A range of half-lives from 6.6 +/- 0.67 minutes to over 100 minutes, relative to the stability of the 18S rRNA control, has been obtained for fifteen mRNAs. They include the pyruvate kinase and actin mRNAs, as well as 13 randomly picked mRNAs of unknown function. The mRNAs clearly fall into two populations when their lengths and half-lives are analysed; one population is considerably more stable than the other when mRNAs of similar length are compared. Also, within each population, there is an inverse relationship between mRNA length and half-life. These results suggest that mRNA length and at least one additional factor strongly influence mRNA stability in yeast.

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A comparison between the half-lives of 10 specific yeast mRNAs and their distribution within polysomes (fractionated on sucrose density gradients) was used to test the relationship between mRNA translation and degradation in the eukaryote Saccharomyces cerevisiae. Although the mRNAs vary in their distribution across the same polysome gradients, there is no obvious correlation between the stability of an mRNA and the number of ribosomes it carries in vivo. This suggests that ribosomal protection against nucleolytic attack is not a major factor in determining the stability of an mRNA in yeast. The relative lengths of the poly(A) tails of 9 yeast mRNAs were analysed using thermal elution from poly(U)-Sepharose. No dramatic differences in poly(A) tail length were observed amongst the mRNAs which could account for their wide ranging half-lives. Minor differences were consistent with shortening of the poly(A) tail as an mRNA ages.

The concentrations of anti-oxidant enzymes such as superoxide dismutase (SOD), catalase (CAT) and selenium-dependent glutathione peroxidase (SeGPx), and low molecular weight free-radical scavengers such as reduced glutathione (GSH) and ascorbic acid (vitamin C) were evaluated during the period from gastrulation (GS) to 25 days post-hatch (dph) in the larvae of Asian Seabass, Lates calcarifer. Oxidative damage due to lipid peroxidation (LPO) was also assessed, by evaluation of the formation of malondialdehyde (MDA). All the three anti-oxidant enzymes, SOD, CAT and GPx, showed high activities during gastrulation, suggesting an increased metabolic rate during the period of embryonic development. Though the SOD activity apparently decreased progressively during 3-20 dph of larval development, the difference was not significant. CAT showed high activity during gastrulation and remained constant up to 3 dph, suggesting an increased need to metabolise hydrogen peroxide (H2O2) and organic peroxides. In contrast, SeGPx activity increased progressively from 5 dph to 25 dph during larval development, indicating an increased need to detoxify lipid peroxides. This is evident from the observation of increased lipid peroxidation from 10 dph to 25 dph during larval development. GSH levels were low at gastrulation, indicating increased metabolic rate and formation of lipid radicals during this period, corresponding to the decrease in the level of ascorbic acid, which is consumed for regeneration of GSH.

Luminescent Vibrio harveyi is a natural microflora of marine and coastal water bodies and is associated with mortality of larval shrimp in penaeid shrimp hatcheries. It is also known that the bacteriophages occur virtually in all places where their hosts exist. In this study, distribution of luminescent V. harveyi and the bacteriophages affecting these hosts was examined in a commercial Penaeus monodon hatchery during three shrimp larval production cycles, including a cycle affected by luminescent bacterial (LB) disease outbreak.Out of a total of 1195 samples drawn from seawater source, sand-filtered water, nauplius, zoea, mysis and post larval rearing tanks, maturation and spawning tanks, Artemia hatching tank and algal culture tanks processed using conventional microbiological techniques, 21.4% of the samples harboured luminescent bacteria. During the larval production cycle affected by LB disease (LBD), luminescent V. harveyi could be recovered from 52% of the hatchery samples, whereas during luminescent bacterial disease-free larval production cycle (LBDF), these bacteria could be recovered from only about 9% of the samples. The predominant source of luminescent bacteria was the brood shrimp and their rearing tanks in maturation and spawning facilities. 73% of the maturation and 80% of the spawning tank water samples harbored LB during LBD, whereas, only 20% and 32% of the maturation and spawning tanks respectively harbored LB during LBDF. LB could be isolated from 17% of the water samples in tanks from nauplius stage onwards with increasing counts that subsequently lead to LB disease.Bacteriophages affecting the luminescent V. harveyi could be isolated from as many as 36% (21% and 43% of the samples analysed during LBDF and LBD respectively) of a total of 181 water samples drawn from various sources in the hatchery, using 27 luminescent V. harveyi hosts by agar overlay technique. The maturation tank water samples were found to be the predominant source of bacteriophages, followed by spawning tank water samples as observed with the LB. Sixty five bacteriophages, 13 during LBDF and 52 during LBD were isolated, which were grouped in to seven types based on their plaque morphology.The study has indicated that the brooders, maturation and spawning facilities in the shrimp hatchery are the main source of luminescent V. harveyi and their bacteriophages and that occurrence of LB even in low counts during early larval stages can possibly lead to development of LB disease despite presence of bacteriophages in the larval rearing tanks.