Monodon Juveniles Research Articles

Efficacy of aromatic plants Zingiber officinale and Syzygium aromaticum extracts as natural immunostimulants on survival, growth performance, and immune response of farmed prawn Penaeus monodon juveniles

Efficacy of aromatic plants Zingiber officinale and Syzygium aromaticum extracts as natural immunostimulants on survival, growth performance, and immune response of farmed prawn Penaeus monodon juveniles

Contrasting nursery habitats promote variations in the bioenergetic condition of juvenile female red squat lobsters (Pleuroncodes monodon) of the Southern Pacific Ocean.

The red squat lobster Pleuroncodes monodon is an important fishery resource in the Humboldt Current System (HCS). This decapod is exploited in two fishing units: (a) the northern fishing unit (NFU, from 26°S to 30°S) and (b) the southern fishing unit (SFU, from 32°S to 37°S), each of which have an adjacent nursery area that is the source of recruits to replace the exploited adult populations (in the NFU: off the coast of Coquimbo (28°S) and in the SFU: off the coast of Concepción (36°S)). Marked spatial differences in the environmental conditions of the NFU and SFU, and the biogeographic break that exists between these nursery areas (30°S) may promote changes in the bioenergetic condition of new P. monodon juveniles. To evaluate this, we analyzed the bioenergetic condition (measured as: body mass, lipids, proteins, glucose, and energy) of new juvenile females in the main nursery areas off the Chilean coast. The juvenile females from the SFU showed a higher body mass than those from the NFU. Consistently, the juvenile females from the SFU had a higher content of lipids, proteins, and glucose than those from the NFU, indicative of higher energy contents and a higher lipid/protein ratio in the south compared to the north. Considering the current overexploitation of this fishery resource in the HCS, it is essential to understand how the bioenergetic condition of juvenile females of P. monodon may vary in nursery areas at different latitudes in order to generate sustainable fishery management policies with an ecological approach, designed specifically to each fishing unit. Furthermore, identifying the latitudinal variations of these biochemical compounds in P. monodon juveniles can elucidate the geographic origin of red squat lobsters that present a ”better bioenergetic condition” in the HCS, which may significantly benefit sustainable fishing certification processes.

Effect of different experimental diets and salinity on growth performance of Penaeus monodon

This study evaluated the effect of different experimental diets on the growth of Penaeus monodon cultured at different salinities. We used four diets in this experiment, such as diet-1 (F1), diet-2 (F2), diet-3 (F3) and diet-4 (F4). All the diets were fed to P. monodon juveniles cultured at salinities of 5 ppt (S5), 10 ppt (S10), 15 ppt (S15), and 20 ppt (S20) for a 45-day tank trial. In this study, the feed’s fishmeal protein was replaced with concentrated protein as an alternative approach to aquaculture sustainability. There was no interaction effect and no main effects of feed and salinity on the growth of P. monodon. Feed and salinity had an interaction effect, and salinity had a main effect on the survival of P. monodon. Overall, survival was higher in the tanks with higher salinity, such as 15 ppt and 20 ppt. There was also a higher survival at salinity 10 ppt where shrimps were fed with F1 (83.33±3.33%) and F2 (86.67±8.82%). Estimated marginal survival also indicated that survival tends to be raised with increased salinity. There was an environmental fluctuation during this study. Hence, this data might not indicate the general features of growth and survival of P. monodon.

Oral administration of white spot syndrome virus surface proteins VP24 and VP28 modulates immune gene expression in Penaeus monodon juveniles

Being primitive organisms, crustaceans such as shrimp and crab rely on innate immunity to defend pathogens. White spot syndrome virus is a deadly pathogen that causes total mortality in farmed shrimp. Although shrimps do not possess an adaptive immune system and immune memory, there are efforts to prevent mass mortality due to WSSV through the administration of antigenic proteins derived from the virus. In this paper, we describe the effectiveness of the two major WSSV antigenic proteins, VP24 and VP28, in eliciting an immune response in shrimp. Recombinant proteins rVP28 and rVP24 were mass-produced in E. coli and orally administered to Penaeus monodon juveniles. During the administration of recombinant antigens, differential expression analysis of shrimp biodefense genes was carried out. Among the genes analyzed, transcripts of TLR, Syntenin, PmRACK, Rab7, SOD and C-type Lectin exhibited upregulation during the administration of both rVP28 and rVP24 at least at a one-time point. Independently, rVP28 administration upregulated Lectin, PmRACK, Rab7, SOD, STAT, TLR and Syntenin genes at least at one-time point. Penaeidin and Crustin are either downregulated or similar to that of control. The rVP24 administration upregulated Crustin, Lectin, Penaeidin, PmRACK, Rab7, SOD, TLR and Syntenin. The STAT was either downregulated or similar to that of the control at least at one-time point. The results revealed the extent of the antigenic property and the ability of rVP28 and rVP24 to elicit an immune response after oral administration.

Inter‐sexual comparison of body biomass, proximate biochemical composition, and fatty acid profiles of new juvenile squat lobsters (Pleuroncodes monodon) in the Southeast Pacific Ocean

AbstractIn the wide distribution range of the red squat lobster Pleuroncodes monodon in the Southeast Pacific Ocean, there is an important nursery area on the southern coast of Chile. The new juvenile individuals from this nursery area are directly recruited into the adult squat lobster population, which is exploited by industrial fisheries. Despite the importance of new P. monodon juveniles for recruitment estimations in fishery management models, their bioenergetic condition and/or nutritional status at the onset of their benthic phase remain unknown, as are the differences in the biochemical composition and energy reserves of the two sexes, which could help explain the cost of the first breeding event in females. Therefore, in new juvenile squat lobsters with the same degree of immaturity, we quantified and compared between the sexes (female vs. male): the size (cephalothorax length, CL), body biomass (dry weight and organic matter), biochemical composition (proteins, glucose, and lipids), and fatty acid profiles (FAs). The results indicate that the CL of new juveniles was similar between the sexes, while the dry weight and organic matter presented significant differences, with higher values in new juvenile females (NJF) than new juvenile males (NJM). Similarly, the NJF had a higher content of proteins, glucose, and lipids than NJM. The FAs also showed significant differences between the sexes; the NJF had a higher content than NJM in all fatty acid classes (i.e., saturated, monounsaturated, and polyunsaturated), with the FAs DHA (C22:6n‐3), EPA (C20:5n‐3), oleic (C18:1n‐9), palmitic (C16:0), and eicosatrienoic (C20:3n‐3) significantly contributing to the differentiation of FA profiles between the sexes. All of the aforementioned differences among the multiple variables of the bioenergetic condition can indicate biochemical adaptations in the storage capacity of energy reserves, particularly among NJF that must support the high energy cost of the first reproductive event (characterized by embryo production and incubation), which occurs during the austral winter, a period predominated by cold‐water temperatures and scarce food availability in the habitat. Overall, our findings have significant implications in fishery management models. In this case, defining the bioenergetic condition of the new juvenile squat lobsters can aid in predicting the density and stability of the adult population, which is exploited by commercial fisheries.

Feeding Behaviour and Bioavailability of Essential Amino Acids in Shrimp Penaeus monodon Fed Fresh and Leached Fishmeal and Fishmeal-Free Diets.

Simple SummaryWhile success has been achieved with replacing fishmeal entirely in diets for whiteleg shrimp Litopenaeus vannamei, giant tiger prawn Penaeus monodon still requires fishmeal for optimum culture performance. Crystalline amino acid (CAA) supplementation is becoming popular in shrimp feed formulation and is needed in low fishmeal diets as common alternative protein sources are typically deficient in essential amino acids, such as methionine and lysine. Furthermore, the slow feeding behaviour of shrimp compared to other cultured aquatic species means that feeds can lose specific nutrients before they are consumed. In particular, highly soluble CAA are prone to leaching. In this study, we examined the feeding behaviour, CAA leaching loss and AA uptake in large Penaeus monodon juveniles through a series of short-term experiments using a terrestrial meal-based formulation (TM) enriched with CAA and a traditional fishmeal-based formulation (FM). Feeding behaviour and nutrient bioavailability was found to be similar for the two diets. However, leaching over as little as 60 min had a major impact on AA absorption for the TM diet. The growth implications associated with leaching losses need to be investigated. However, the results indicate the need for careful feeding management as increased reliance on CAA for P. monodon culture could lead to suboptimal nutrition.The complete replacement of fishmeal with terrestrial meals did not have a negative impact on the attractiveness, palatability, and apparent digestibility of the formulation. Shrimp were found on average to eat more and have similar appetite revival on the terrestrial meal-based formulation (TM) diet compared to the traditional fishmeal-based formulation (FM) diet. However, methionine (Met) and lysine (Lys) leached out rapidly from the TM diet, and as a result, this initially overfortified diet showed lower levels of those AA in comparison to FM after 60 min immersion. Both dietary Lys and Met were sub-optimal in TM within 120 min of immersion, whereas in comparison, the FM diet supplied consistent levels of EAA for up to 240 min immersion. Nonetheless, shrimp fed fresh TM had significantly higher peak haemolymph concentrations at 30 and 60 min for total AA, Met, and Lys than FM-fed shrimp. The over-supply of CAA far compensated leaching losses, and CAA were well absorbed and used by the shrimp within 120 min, with no obvious signs of asynchronous absorption of CAA to protein-bound AA. However, shrimp fed the TM diet that had leached out for 60 min, had haemolymph concentrations of Met and Lys that were only 41% and 44% of the ones on fresh feed respectively, while there was a negligible effect of leaching on FM. This study provides further insight into the feeding behaviour and bioavailability of dietary amino acids for P. monodon juveniles.

Effects of seaweeds extract on growth, survival, antibacterial activities, and immune responses of Penaeus monodon against Vibrio parahaemolyticus

Seaweeds can play an essential role in controlling antibiotic resistance for bacterial diseases. Three extracts of two brown seaweeds Padina tetrastromatica and Sargassum ilicifolium were investigated as growth promoters and to provide immune protection against Vibrio parahaemolyticus. Extracts of the two seaweeds were administered at 2.5 and 5 g kg−1 with food for 45 days to Penaeus monodon juveniles. The maximum weight gain (6.28 and 7.08 g), specific growth rate (3.39 and 3.32%), and survival rate (78.45 and 82.45%) of the juvenile tiger shrimp were obtained at a dose of 5 g kg−1 with P. tetrastromatica extracted by methanol and ethanol, respectively; which was significantly higher than the other solvents and control group (p < .01). On the other hand, methanol extract of both seaweeds had maximal antibacterial activity against V. parahaemolyticus with zones of inhibition ranging between 20.25 ± 1.00 and 22.00 ± 0.50 mm. The minimal time required for haemolymph clotting was with methanol extracted of P. tetrastromatica at 5 g kg−1, which was significantly lower than the other groups (p < .05). After challenging with V. parahaemolyticus, the total haemocyte count (THC) in P. monodon treated with methanol-extract of P. tetrastromatica diet at 5 g kg−1 was higher (5.42 × 105 cells mL−1) but not significantly different than the other diets (p > .05). However, the administration of 5 g kg−1 methanol and ethanol extract of P. tetrastromatica improved growth performance and the immune capacity of P. monodon by increasing their phenoloxidase activity, superoxide anion concentration, and resistance against V. parahaemolyticus. HIGHLIGHTS The maximum growth performance and survival of juvenile tiger shrimps obtained with Padina tetrastromatica extract at a dose of 5 g kg−1. The methanol extract of P. tetrastromatica and Sargassum ilicifolium had maximal antibacterial activity against V. parahaemolyticus. The administration of 5 g kg−1 methanol and ethanol extract of P. tetrastromatica improved growth performance and the immune capacity of P. monodon.

Antiviral activity of Cynodon dactylon on white spot syndrome virus (WSSV)-infected shrimp: an attempt to mitigate risk in shrimp farming

White spot syndrome virus (WSSV) is the most contagious pathogen causing huge economic losses in the shrimp industry worldwide. Several medicinal plants are known to have antiviral activity through the inhibition of viral diseases in fish and shellfish. Hence, there is a need to investigate the ability of natural remedies like plant sources to mitigate this devastating disease in crustaceans. This study was carried out to test the antiviral activity of ethanolic extract of Cynodon dactylon on WSSV in tiger shrimp Penaeus monodon juveniles with an average weight of 13.541 ± 2.927 g. Different doses of the extract (75, 100, and 150 mg/kg) were administrated in vivo through intramuscular injection. The antiviral activity was determined by observing survival rates, and WSSV infection was confirmed at the end of the experiment through polymerase chain reaction (PCR) identification. Before the in vivo experiment, presence of antiviral compounds ((+)-catechin, vanillic acid, syringic acid, (−)-epicatechin, p-coumaric acid, and quercetin bioactive compounds) in C. dactylon was confirmed through high-performance liquid chromatography with diode-array detection (HPLC-DAD) analysis. The results obtained in this study show that a dose of 100 to 150 mg/kg body weight ethanolic extract of C. dactylon prevented the infection of WSSV marked by 100% survival and absence of WSSV-specific band using nested diagnostic PCR, thus demonstrating the suitability of ethanolic extract of C. dactylon as a possible prophylactic for the prevention of WSSV infections in shrimp culture.

Salinity Tolerance of Wild Penaeus monodon and Penaeus indicus Juveniles: Perspectives of Their Sustained Availability in Sundarban

Sundarban estuaries are natural nurseries of Penaeus monodon and P. indicus shrimps that fetch high economic values. We studied salinity (0 to 40) tolerance (96 h exposure without acclimation) of their juveniles (PL-5, wild varieties) under ambient temperature. P. monodon and P. indicus juveniles showed limited ability of tolerating freshwater and high salinity. Overall juveniles survived better in salinity 5 to 20, however, P. monodon juveniles showed a better salinity tolerance than P. indicus juveniles. Increasing salinity of Sundarban estuaries may negatively affect sustained availability of P. monodon and P. indicus seeds in the wild.

Strain variability and pathogenic potential of tdhcarrying Vibrio parahaemolyticus isolated from diseased Penaeus monodon

A disease outbreak in 42-d-old black tiger shrimp Penaeus monodon juveniles from a commercial aquaculture farm in Kerala, India, was investigated. The cause of the disease outbreak was confirmed as Vibrio parahaemolyticus by biochemical tests, PCR targeting the toxR gene and pathogenicity testing of the isolates. All of the isolates tested negative by PCR specific for V. parahaemolyticus associated with acute hepatopancreatic necrosis disease (AHPND), implicating vibriosis unrelated to AHPND as the cause of mortality. Among the 19 isolates obtained, 2 possessed the tdh gene (coding for thermo-stable hemolysin), whereas none of the isolates possessed trh. The LD50 value of 8 isolates of V. parahaemolyticus from diseased and apparently healthy shrimp ranged from 2.7 × 104 to 4.9 × 105 CFU ml-1 by immersion challenge of P. monodon postlarvae. BOX-PCR and dendrogram analysis of the bacterial isolates revealed that the isolates from moribund and apparently healthy shrimp formed separate clusters, indicating that these isolates originate from separate clones. The isolates from moribund shrimp including tdh-positive V. parahaemolyticus clustered together. The present study represents the first report of tdh-positive V. parahaemolyticus causing disease in a shrimp farm.

Microbial biomass, marine invertebrate meals and feed restriction influence the biological and gut microbiota response of shrimp Penaeus monodon

P. monodon juveniles were fed krill meal (KM), krill hydrolysate (KH), whole squid (SQ), and the microbial biomass, Novacq™ (NQ), at 10% inclusion, in practical fishmeal and soybean meal based diets. Diets were fed to apparent satiation as well as restrictively pair-fed (~60% of control diet satiation) for 6 weeks to examine the effects of the test ingredients and feed restriction on shrimp growth, feed efficiency, digestive enzyme activity, nutritional condition, and gut microbiota.All diets when fed to satiety significantly outperformed the control diet, with shrimp fed NQ 87%, SQ 73%, KH 41% and KM 38% larger than shrimp fed the control diet. NQ fed shrimp had the best feed conversion ratio (FCR) and significantly improved retention efficiency (RE) of dietary lipid (RETL), protein (RECP) and gross energy (REGE). SQ significantly promoted feed intake over control and KM fed shrimp, but neither KM, KH nor SQ improved RETL, RECP or REGE. While there was little change in the apparent digestibility (AD) of each diet, the apparent biological value (ABV) of lipid (ABVTL), protein (ABVCP) and gross energy (ABVGE) were significantly improved by inclusion of NQ; and ABVTL and ABVGE were significantly improved by addition of SQ. Feed restriction had a stronger effect on hepatopancreas digestive enzymes and gut microbiota than addition of any feed ingredient. Total protease activity was positively correlated with feed efficiency, including FCR, RETL and REGE. Shrimp fed to satiety tended to have high levels of Vibrio whereas those on the restricted ration tended to have higher levels of bacteria in Rhodobacteracaea, Flavobacteriales and Bacteroidales.We conclude that shrimp are more efficient in using digested dietary macronutrients for growth when whole squid and Novacq™ are provided, due to improvements in feed intake and post-absorptive processes. Feeding restriction was shown to be a useful strategy to improve P. monodon feeding efficiency, digestive capacity and modulate gut microbiota, however it reduced the scope for shrimp growth especially on high performing diets. Novacq™ was more effective than some of the known invertebrate meals and a more environmentally sustainable growth and nutrient utilisation promoter for shrimp.

Integration of substrate in biofloc based system: Effects on growth performance, water quality and immune responses in black tiger shrimp, Penaeus monodon culture

To evaluate effect of substrate integration in biofloc based system, a 52-day growth experiment was conducted using black tiger shrimp, Penaeus monodon juveniles (3.32 ± 0.07 g). The factorial design consisted of floc, F (with or without) as first factor and substrate (bamboo mat, B; nylon mesh, N; and without substrate) as second factor. This resulted six treatments; F + B, F + N, F, B, N and a control without biofloc and substrate. Shrimps were stocked at 110 nos. m–3 in Fibre Reinforced Plastic (FRP) tanks and, rice flour was used as carbon source in biofloc based treatments. Incorporation of nylon mesh and bamboo mat in biofloc system trapped 31.3%–38.6% and 8.5%–13.5% total suspended solids respectively and reduced bottom solid deposition. Among the substrate based groups, significantly better development of biofilm with higher microbial population noticed in F + B compared with nylon mesh. Similarly, significantly higher final growth (p < 0.01) was recorded in F + B system followed by F + N while no significant difference in body weight recorded among floc, F or substrate based groups (B, N). Biofloc and substrate integration (F + B and F + N) resulted significantly (p < 0.01) lower feed conversion ratio compared to control and floc. Incoporation of bamboo substrate in biofloc, (F + B) improved shrimp immune responses through higher hemocyte counts and prophenoloxidase activity compared to other treatments. The study revealed that integration of substrate in the biofloc system improved growth performance, FCR and immune parameters in shrimp by trapping the suspended biofloc particles, better water quality parameters, enhanced biofilm growth and provision of quality natural food.

Substrate based black tiger shrimp, Penaeus monodon culture: Stocking density, aeration and their effect on growth performance, water quality and periphyton development

Growth performance of black tiger shrimp Penaeus monodon juveniles were evaluated in two outdoor experimental trials as a function of two stocking densities and aeration system in substrate based shrimp culture. The experiment 1 had 2 × 2 factorial design with two levels of stocking density and two management systems (with and without substrate addition) resulting in four treatment, each with three replicates. The 12 FRP tanks (1000 L) were stocked with P. monodon juveniles (1.08 ± 0.12 g) at 10 and 20 m2 as first factor, and with substrate (10 + S and 20 + S) and without substrate (10-S and 20-S) as second factor. In experiment 2, effect of aeration in substrate system was evaluated in 1000 L FRP tanks with P. monodon (3.89 ± 0.12 g) in four treatments: provision of aeration (A) with substrates (S + A), without substrate (C + A), and absence of aeration with (S-A) or without substrate (C-A). In both experiments, bamboo substrates (5 × 2 × 1 cm) were installed in substrate based groups which generated an additional 540 cm 2 surface area for periphyton development. Formulated feed containing 38% crude protein was provided in both the experiments. In trial 1, stocking density did not significantly affect water quality parameters, whereas provision of bamboo substrate significantly reduced nitrate-N level (P < .05). Both stocking density and substrate addition played significant role in shrimp survival by 14–30% improvement due to substrate addition while 18–34% changes in survival due to stocking density. The substrate addition improved FCR significantly (P < .05) by 21–33% compared to without substrate based treatments. In experiment 2, lack of aeration significantly affected the dissolved oxygen level (P < .05) in the water column, while it does not significantly affected the growth parameters, and substrate addition alone improved 21% of survival rate of shrimp. Estimation of periphyton biomass revealed that stocking density and aeration effects resulted 60 and 40% significant (P < .05) difference in ash free dry matter in periphyton biomass. From the present trials, it can be concluded that stocking density of shrimp plays an important role in optimum utilization of periphyton developed over submerged substrates. Also, insignificant growth performance of shrimps reared in low density substrate based systems without aeration indicated that the system has the potential to adopt by small scale shrimp farmers for sustainable ecofriendly farming.

Fermented Copra Meal as Replacement for Dietary Fish Meal Protein in Grow-Out Culture of Black Tiger Shrimp, Penaeus monodon Juveniles

Feeding trials were conducted to assess the effects of diets containing fermented copra (FCM) as an alternative to fish meal (FM) on growth, survival, and feed efficiency, in Black Tiger Shrimp, Penaeus monodon. A diet was formulated where 40% of the FM protein was replaced by FCM protein, and compared with a commercial shrimp diet. The feeding experiments were carried out using 10-ton capacity circular outdoor tanks. Three hundred and fifty (350) shrimp were stocked in each tank at a density of 35 shrimp per m3. They were fed the diets at a rate which decreased from 15% down to 4% of average body weight (ABW) per day. The results demonstrated that growth, survival, and feed performance, in P. monodon in outdoor tanks were not affected by replacing 40% of the dietary FM with FCM protein. Furthermore, no difference was found in proximate composition of the shrimp carcass fed the commercial and experimental diets. Although protein efficiency ratio (PER) of the commercial and FCM-based diets were similar, protein productive value (PPV) was significantly higher in the FCM than the commercial diet. Hence, we concluded that FCM is a promising alternative protein source for Black Tiger shrimp and can replace 40% of the fish meal protein without adversely affecting growth, survival, and feed efficiency.

Physiological performance and serum Na+, K+ Ca2 + and Mg2 + regulation of black tiger prawn (Penaeus monodon Fabricius 1798) reared in varying Na+/K+ ratios of inland saline water

A 28-day trial was conducted to investigate the serum ionic regulation of juvenile black tiger prawns (Penaeus monodon Fabricius 1798) of 1.2±0.1g mean initial weight, reared in varying Na+/K+ ratios of inland saline water (ISW). The serum Na+, K+, Ca2+ and Mg2+ regulation, osmoregulatory capacity (OC), isosmotic points, survival, growth and condition indices of P. monodon were measured when P. monodon were reared in four different ISW types having Na+ and K+ ratios of 119.4 (represented by raw ISW control having higher Na+/K+ ratio), 6.5, 12,0 and 16.2. The first water type of ISW (control) was at 5ppt (ISW5) and the other 3 were at the salinities of 5ppt (ISWK5), 10ppt (ISWK10) and 15ppt (ISWK15) which were fortified with K+ equivalent to [K+] in the ocean water of 25ppt. P. monodon juveniles reared in ISW5 and ISWK15 regulated their serum Na+ and K+ stronger than juveniles reared in ISWK5 and ISWK10 and brought the serum Na+/K+ ratios closer to the normal Na+/K+ ratio of OW. Serum Ca2+ and Mg2+ of the juveniles reared in ISWK10, were regulated strongly over the trial period. However, the juveniles reared in ISW5 and ISWK15 had increased serum Ca2+ at day 28. After 14days of rearing, the serum osmolality of juveniles decreased significantly from 640.2 and 649.6mOsm to 550.1 and 562.2mOsm in ISWK5 and ISWK10 respectively. In contrast, the serum osmolality and OC of juveniles reared in ISW5 (control) remained constant over the 14day period but then increased significantly toward the end of the trial. During the initial 14days of rearing, 20.8 and 20.5% of the juveniles survived in ISWK5 and ISWK10 respectively. However, 100% of juveniles died at the end of the trial. In contrast, the juveniles reared in ISW5 and ISWK15 were able to survive until the end of the trial with a survival rate of 37.5 and 62%, respectively. At the end of the trial, the SGR and condition indices of juveniles reared at ISW5 and ISWK15 showed no significant difference (P<0.05). At day 14, the amount of food ingested by the juveniles reared in ISWK5 and ISWK10 were significantly lower than the juveniles reared in ISW5 and ISWK15. The exoskeleton moisture content (EM %) and dry exoskeleton index (Ebd) of juveniles reared in ISW5 were significantly higher and lower respectively, than the EM % and Ebd of juveniles reared in ISWK15. This trial suggested that P. monodon juveniles faced unfavourable medium Na+ and K+ ratio in ISW through strong regulation of [Na+] and [K+] which enabled the prawns to establish normal ratios of Na+ and K+ in their haemolymph ranging from 21.42 to 25.97mg/L which were similar to the normal haemolymph ratio of Na+ and K+ of prawns reared in OW ranging from 22.3 to 29.9.

Investigations on white spot disease outbreak in Penaeus monodon (Fabricius, 1798) in association with Vibrio mimicus infection in the Sunderbans, West Bengal, India

The present study investigated the outbreak of white spot disease (WSD) in association with Vibrio mimicus infection, which occurred twice consecutively in a black tiger shrimp (Penaeus monodon) farm located in the Sunderbans, West Bengal, India. The farm stocked with post-larvae (PL) @ 16 PL m-2, encountered disease outbreak on the 41st day of culture (DOC) followed by a second outbreak on the 54th DOC with 100% mortality each time. Shrimp samples were collected for molecular diagnosis as well as for microbiological investigations. White spot syndrome virus (WSSV) infection was confirmed by polymerase chain reaction (PCR). V. mimicus isolated from the outbreak, was characterised by morphological, physiological and biochemical characteristics. V. mimicus isolated was found to be pathogenic by challenge studies which caused 100% mortality in P. monodon juveniles. Microbial load was studied in the natural infection and also in challenge trials in relation to the day of advancing infection. LD50 value for V. mimicus, isolated from the outbreak, was 107.32 in P. monodon juveniles. Co-infection of V. mimicus with WSSV led to 100% mortality within seven days from the onset of clinical signs.

Dietary biofloc supplementation in black tiger shrimp,Penaeus monodon: effects on immunity, antioxidant and metabolic enzyme activities

A 60-day indoor experiment was conducted to study the effect of dietary supplementation of biofloc on metabolic enzyme activities and immune responses in Penaeus monodon juveniles. Biofloc developed in indoor fibreglass-reinforced plastic (FRP) tanks (1000 L) was used as dietary supplement in P. monodon (2.90 ± 0.10 g) reared in 1000-L FRP tanks. Graded level of dried biofloc was included in shrimp basal diets, 0% (control, B0), 4% (B4), 8% (B8) and 12% (B12). The level of metabolic enzymes like malate dehydrogenase (MDH), aspartate aminotransferase (AST) and alanine aminotransferase (ALT) was not significantly different with control up to 8% dietary supplementation. A higher level of total haemocyte count (THC) was noticed in B8 (22.16 ± 2.17 × 106 cells mL−1) and B4 (21.11 ± 0.56 × 106 cells mL−1) compared with control, C (14.61 ± 2.74 × 106 cells mL−1). Biofloc-supplemented groups recorded significantly higher (P < 0.05) serum SOD and catalase activity (P < 0.01) in comparison with control. The groups fed with 4% dietary biofloc supplement recorded highest relative percentage survival (RPS), 45% after challenge with Vibrio harveyi followed by 36% and 27% RPS in B8 and B12 groups. Based on these results, it can be concluded that supplementation of biofloc even at 4% level in the feed improves immune responses and metabolic activities in black tiger shrimp juveniles.

Expression profile of key immune-related genes in Penaeus monodon juveniles after oral administration of recombinant envelope protein VP28 of white spot syndrome virus

White spot syndrome virus (WSSV) is the most catastrophic pathogen the shrimp industry has ever encountered. VP28, the abundant envelope protein of WSSV was expressed in bacteria, the purified protein administered orally to Penaeus monodon juveniles and its immune modulatory effects examined. The results indicated significant up-regulation of caspase, penaeidin, crustin, astakine, syntenin, PmRACK, Rab7, STAT and C-type lectin in animals orally administered with this antigen. This revealed the immune modulations in shrimps followed by oral administration of rVP28P which resulted in the reduced transcription of viral gene vp28 and delay in mortality after WSSV challenge. The study suggests the potential of rVP28P to elicit a non-specific immune stimulation in shrimps.

Effects of biofloc under different carbon sources and protein levels on water quality, growth performance and immune responses in black tiger shrimpPenaeus monodon(Fabricius, 1978)

A 75-day 2 × 3 factorial experiment was conducted to evaluate the effect of two levels of dietary protein (32 and 40%) and two different carbon sources (rice flour–R and molasses-M), and without carbohydrate (control–C) in black tiger shrimp Penaeus monodon juveniles (3.37 ± 0.04 g) at 100 nos. m−3 in 100 L fibre reinforced plastic tanks. Biofloc volume and total suspended solid were higher in molasses added groups (32 + M and 40 + M) followed by rice flour (32 + R and 40 + R) and controls (32C and 40C). Molasses and rice flour addition significantly reduced (P < 0.01) the total ammonia–N compared to controls. The highest Vibrio, Bacillus and Lactobacillus counts were recorded in 40 + M, 32 + M and 32 + R respectively. Among the treatments, significantly higher (P < 0.01) final body weight was recorded in 40 + R (8.5 ± 0.3 g), 40 + M (7.8 ± 0.3 g) and 32 + R (7.5 ± 0.4 g) compared to control groups, 32C (6.1 ± 0.3 g), 40C (6.4 ± 0.3 g) and molasses added group, 32 + M (5.7 ± 0.4 g). Rice flour supplementation significantly increased (P < 0.01) the total haemocyte count (×106 cells mL−1) in 32 + R (45.7 ± 3.7) and 40 + R (44.3 ± 3.1) compared to controls, 32C (27.3 ± 3.4) and 40C (25.8 ± 0.9). Similarly, higher superoxide dismutase, catalase, serum protein and glucose were recorded in the rice flour added groups, 40 + R followed by 32 + R. Among the treatments, the highest level of prophenoloxidase (OD 490 nm, 0.3 ± 0.0) and survival after challenge with Vibrio harveyi (55.6%) was observed in 32 + R. The study elucidates that rice flour addition produces optimum level of biofloc with better growth and immune responses compared to molasses and control. Furthermore, rice flour addition at 32% protein level could replace 40% protein feed.

Effects of carbohydrate supplementation on water quality, microbial dynamics and growth performance of giant tiger prawn (Penaeus monodon)

Biofloc technology based 45-day indoor growth trial was conducted to evaluate the effect of carbohydrate (CHO), molasses supplementation on two developmental stages viz, juvenile (J) and sub-adult (SA) of Penaeus monodon in zero-water exchange system. P. monodon juveniles (1.56 ± 0.04 g) and sub-adults (14.32 ± 0.22 g) were stocked in fibre-reinforced plastic tanks (1,000 L) with soil base. Carbohydrate supplementation significantly reduced (p < 0.05) the total ammonia nitrogen (TAN), nitrite-N (NO2-N) and nitrate-N (NO3-N) over the time periods in sub-adult group. However, no significant difference in TAN and NO2-N was observed in juvenile-based treatments. Supplementation of carbohydrate significantly increased (p < 0.05) the water and soil total heterotrophic bacterial (THB) count in both juvenile and sub-adults. Despite increase in total Vibrio count (TVC), lower TVC/THB % was noticed in the water column of J + CHO (0.82) and SA + CHO (0.73) compared to control groups, J − CHO (1.48) and SA − CHO (1.21). Supplementation of carbohydrate increased the final body weight in J + CHO (6.51 ± 0.44 g) and SA + CHO (22.52 ± 0.98 g) compared with respective controls, J − CHO (5.05 ± 0.45 g) and SA − CHO (20.00 ± 0.33 g). Similarly, significantly lower (p < 0.05) feed conversion ratio and better protein efficiency ratio were recorded in carbohydrate-supplemented juvenile and sub-adults treatment groups. The present study demonstrates that supplementation of carbohydrate reduced the nitrogenous metabolites and significantly enhanced the growth performance of juvenile and sub-adult of P. monodon.