Macrobrachium Rosenbergii Postlarvae Research Articles

Anaesthetic Effect of Clove Basil (Ocimum gratissimum) Essential Oil on Macrobrachium rosenbergii Post-Larvae

Anaesthetic Effect of Clove Basil (Ocimum gratissimum) Essential Oil on Macrobrachium rosenbergii Post-Larvae

Nursery rearing freshwater prawn, Macrobrachium rosenbergii, in biofloc system integrated with red seaweed, Gracilaria tenuistipitata, at different stocking densities under zero water exchange

This study was conducted to assess the effects of stocking densities on the water quality, survival and growth of the freshwater prawn Macrobrachium rosenbergii postlarvae (PL) cultured in a biofloc system integrated with red seaweed (Gracilaria tenuistipitata). Postlarvae prawns weighing 0.012±0.001 g were stocked at densities of 1,000, 1,500, 2,000, and 2,500 PL/m3, noted as D1, D1.5, D2, and D2.5, respectively. Each density treatment was replicated three times and randomly assigned to 12 plastic tanks of 150 l at a salinity of 10 ppt. Red seaweed was added at a rate of 1.5 kg/m3, and molasses was used as a carbon source to maintain a C:N ratio of 15:1. No water exchange occurred during the 30-day rearing period. Results indicated that water quality parameters, including TAN and NO2-, biofloc volume, total heterotrophic bacteria, and Vibrio spp. counts, increased at higher prawn densities but remained within the appropriate range for prawn performance. Growth rate in weight and survival of prawns decreased as stocking density increased, with D1 and D1.5 showing comparable and significantly higher results compared to D2 and D2.5. Prawn production increased with rising stocking density, with a significant difference among treatments (p<0.05). Furthermore, prawns in D1 and D1.5 exhibited significantly higher feed efficiency than those in D2 and D2.5. These findings suggest that nursery rearing of prawn PL at a density of 1,500 ind/m3 in a biofloc system integrated with red seaweed offers optimal growth and feed efficiency, while maintaining good water quality and conserving water resources.

Toxicidade aguda da amônia total para pós-larvas de Macrobrachium rosenbergii em diferentes níveis de salinidades

Abstract Nitrogen compounds, particularly ammonium, nitrite and nitrate, are a major problem in shrimp production systems. These compounds can accumulate in the aquatic environment and reach harmful or even lethal levels. Thus, monitoring the levels of nitrogenous compounds such as ammonia and studying their effects on the animals are essential. One tool used for this purpose is acute toxicity testing based on the evaluation of LC50 values. Furthermore, tools that can help improve the performance of aquatic organisms in culture are needed. The present study aimed to evaluate the effect of salinity on the toxicity of total ammonia to postlarvae of the freshwater prawn Macrobrachium rosenbergii. For this purpose, acute toxicity testing (LC50-96h) was performed using 540 postlarvae with a mean weight of 0.13 g and a mean total length of 2.47 cm, divided into 54 experimental units of two liters each. A completely randomized design in a 3×6 factorial scheme was used, combining three salinities (0, 5, and 10 g.L-1) and six total ammonia concentrations (0, 8, 16, 32, 64, and 128 mg.L-1), with three replicates per combination. The LC50 values for M. rosenbergii postlarvae at 24, 48, 72, and 96 h and their respective confidence intervals (95%) were estimated using the trimmed Spearman-Karber method. The results showed that salinities of 5 or 10 g.L-1 did not reduce the acute toxicity of total ammonia.

The Culture of Freshwater Prawn, <i>Macrobrachium rosenbergii</i> in Kharland (saline) Ponds of Ratnagiri, Maharashtra

The coastal saline soils locally called as ‘Kharland’, though unsuitable for agriculture can be utilized for the culture of prawns and fishes. The Kharland ponds were prepared for the culture by applying lime, cattle dung, urea and single super phosphates in appropriate doses to create suitable environment for culture. The prawn culture was done in two rectangular ponds with an area of 450 m2 (0.045 ha) each. Post-larvae of Macrobrachium rosenbergii were stocked @ 50,000 per hectare. The initial average size and weight of post-larvae stocked were 11.00±3.04 mm and 13.0±5.1 mg in pond P1, and 11.00±3.14 mm and 13.00±8.12 mg in pond P2. The prawns were fed with laboratory-prepared feed @ 10% of the biomass every day. After a period of four months the prawn grew up to 88.0±6.5 mm and 2169.0±3.08 mg in pond P1 and 85.0±4.2 mm and 1980.0±9.8 mg in pond P2. The study suggested possible utilization of Kharland ponds for culture.

Histopathological Investigation of the Giant Prawn Macrobrachium rosenbergii in the Extensive Culture Ponds of Nellore Region, Andhra Pradesh, India

The present study was carried out in Muthukur area of Nellore region of Andhra Pradesh located at 14.29 19 latitude and 80.10383 longitude), India since this area is actively engaged with aquaculture activities of fish and prawn farming. A recent data indicated that 280 to 984 kg per hectare per crop achieved in Macrobrachium rosenbergii under extensive system in a culture period of 180 to 210 with stocking density of 3 to 5 juveniles per square meter. Since the scampi Macrobrachium rosenbergii was the candidate as well as prominent species in that region, histopathological study was carried out to the see quality of the prawn for the present study. During the investigation of shrimp disease in the culture pond, the prawn Macrobrachium rosenbergii were found to die due to swollen head disease having enlargement of cephalothoracic region containing gill, heart and hepatopancreas, etc. Another kind of symptom of black spots were noticed on the dorsal portion of anterior exoskeleton in the cephalothorax region. Enlargement of pigmentary with black spots formed in the periphery of dorsal side of exoskeleton might be due to the presence of suspected white spot syndrome virus. This kind of disease was found to attack commonly in Macrobrachium rosenbergii in most of the culture ponds. Apart from the study of shrimp disease in culture ponds, attempts were also made to identify the disease in the post larvae of Macrobrachium rosenbergii in the hatchery in and around Nellore region. Mass mortality was found to occur in the post larval stages due to a kind of white muscle disease. It has led to great loss of economy not only to the entrepreneurs involved in the hatchery at Nellore region but also to the country as well. WSSV was characterised by prominent eosinophilic to pale basophilic intra nuclear inclusion bodies in hypertrophied nuclei of most commonly in the epithelial cells and connective tissue cells of the above target tissues. Result of the study showed that multiple infection is quite common in the prawn to be cultured once the water quality has become deteriorated and It is suggested that although it is a extensive culture system, water management and supplement of feeds are prerequisite to maintain the pond.

Effect of the probiotic Lactococcus lactis on the microbial composition in the water and the gut of freshwater prawn ( Macrobrachium rosenbergii ) cultivate in biofloc

The prawns fed with Lactococcus lactis obtained 100% survival in the BFT and BFTPROB treatments compared to the CONT (80%). Regarding growth, it was observed in PROB and BFTPROB treatments, the organisms got greater weight (6.3 ± 1.6, 6.8 ± 1.3 respectively) compared to the other treatments. The effect of L. lactis in the bacterial community of Macrobrachium rosenbergii postlarvae (PL’s) with initial mean weight of 0.1 g, and length 1.4 cm in biofloc, was evaluated. A randomized experimental design was used: T1:BFT: biofloc; T2:BFTPROB:biofloc+probiotic; T3:PROB:probiotic; T4:CONT:control; all in triplicate with 60 PL's/treatment. On days 64 and 127, the weight and length of prawns were determined. 15 guts/treatment were extracted and water samples to obtain bacterial DNA. Massive sequencing of 16S rRNA gene of the samples was performed. Metagenomic analysis identified 17 bacteria classes in gut and water samples. The most abundant were Alphaproteobacteria, Gammaproteobacteria, Betaproteobacteria, Flavobacteria, Actinobacteria, and Clostridia with different benefits in the prawns' health. The bacterial community in the intermediate phase was different to the final, maybe for the colonization capacity of certain bacteria that developed in each treatment. However, L. lactis did not affect the microbial community in prawns' gut and culture water, it attributed to the displacement of the microbial community in biofloc and other probiotics, however it was observed a better prawns' growth and survival with biofloc and probiotic treatments.

Application of Transcriptome Analysis to Understand the Adverse Effects of Hypotonic Stress on Different Development Stages in the Giant Freshwater Prawn Macrobrachium rosenbergii Post-Larvae

Salinity is one of the important environmental factors affecting survival and growth of aquatic animals. However, the impact of low-salinity stress on M. rosenbergii post-larvae at different development stages remains elusive. Therefore, the aim of this study was to explore the underlying mechanisms of hypotonic stress at different development stages of M. rosenbergii post-larvae through transcriptome analysis and antioxidant parameters detection. The salinity of the control group was 15 psu (S15) and the hypotonic stress group was 6 psu (S6). Samples were collected at 7 days-post-hatch (dph), 14 dph and 21 dph larvae. The results showed that hypotonic stress caused oxidative damage in post-larvae evidenced by decreased glutathione peroxidase (GSH-Px); superoxide dismutase (SOD); anti-superoxide anion free radical (ASAFR); and increased malondialdehyde (MDA); nitric oxide (NO); and inducible nitric oxide synthase (iNOS) levels. Transcriptome analysis showed that there were 1428, 1187, 132 DEGs including 301, 366, 4 up-regulated genes and 1127, 821, 128 down-regulated genes at 7 dph, 14 dph and 21 dph larvae under hypotonic stress, respectively. Furthermore, GO and KEGG enrichment indicated that hypotonic stress led to dysregulation of immune signals including lysosome and autophagy in the 7 dph larvae. The autophagy-related genes including beclin 1-associated autophagy-related key regulator (Barkor); ubiquitin-like modifier-activating enzyme ATG7 (ATG7); Beclin; autophagy-related protein 13 (ATG13); nuclear receptor-binding factor 2 (Nrbf2); ubiquitin-like-conjugating enzyme ATG3 (ATG3); vacuole membrane protein 1 (VMP1); and autophagy-related protein 2 (ATG2) decreased at 7 dph, and 14 dph larvae, and then increased at 21 dph larvae under hypotonic stress. In the 14 dph and 21 dph larvae, the renin-angiotensin system was activated. In conclusion, our data indicated that hypotonic stress reduced the antioxidant capacity and impaired the immune system in post-larvae, but as development progresses, the adaptability of post-larvae to hypotonic stress gradually increased, and might reach a new homeostasis through the RAS signaling pathway.

Combined effect of ammonia and nitrite for Macrobrachium amazonicum (Heller, 1862) and Macrobrachium rosenbergii (De man, 1879) post-larvae

This study aimed to determine the median lethal concentration (LC50) of total ammonia and nitrite's combined effect for Macrobrachium amazonicum and Macrobrachium rosenbergii post-larvae at 96 h of exposure and then present their safety levels. In the trial 640 post-larvae of M. amazonicum (2.2 ± 0.2 cm and 0.08 ± 0.02 g) and 640 post-larvae of M. rosenbergii (2.2 ± 0.3 cm and 0.07 ± 0.02 g) were distributed in a completely randomized 4 × 4 factorial design, consisting of four concentrations of total ammonia (0, 11, 22 and 44 mg.L−1 NH4Cl) and four concentrations of nitrite (0, 0.5, 1.5 and 3 mg.L−1 NaNO2) with four replicates for each treatment. All total ammonia concentrations were combined with all nitrite concentrations. According to the LC50 96 h obtained from the combined compounds, the safety levels for both species were determined, being 2.39 mg.L−1 of total ammonia and 0.14 mg.L−1 of nitrite for M. amazonicum. In contrast, for M. rosenbergii, the value was 2.50 mg.L−1 of total ammonia and 0.15 mg.L−1 of nitrite. Moreover, the additivity index demonstrated that, when combined, the compounds have an antagonistic effect on prawns. Additionally, considering the results obtained for both species, it was concluded that M. rosenbergii is more resistant to the combined effect of total ammonia and nitrite than M. amazonicum under the experimental conditions evaluated.

Effects of Artifical Substrate on Rearing of Macrobrachium Rosenbergii Post-larvae in Pond Net Cage

Two experiments were carried out to evaluate the effects of addition of net piece substrates in cages for nursery rearing of freshwater prawn, Macrobrachium rosenbergii post-larvae. In the first experiment, net piece substrates were added with an arrangement to increase the surface area of nursery cages to 50% and 75% and compared with cages without any substrate (control). In the second experiment, maintaining surface area increment at 75% in all cages, the net piece substrates were arranged in three different orientations of horizontal, vertical, and 45o angle sloping. Experiments were conducted in a pond of Faculty of Fisheries, Bangabandhu Sheikh Mujibur Rahman Agricultural University, Gazipur, Bangladesh for a period of 45 days in June –August of 2015 and 2016. A completely randomized design was followed to assign the treatments with three replications. The 75% area increment group showed significantly higher (P < 0.05) growth (1.02 ± 0.09 g) and survival rate (79.43 ± 1.63%), compared to 50% area increment (0.96 ± 0.05 g and 75.03 ± 2.45%) and control group (0.79 ± 0.06 g and 66.66 ± 3.57%). The vertically oriented substrate group showed significantly lower growth 0.95 ± 0.04 g) and survival (76.33 ± 1.15%), compared to the horizontal (1.06 ± 0.05 g and 77.12 ± 1.20%) and sloping (1.16 ± 0.10 g and 79.33 ± 0.57 %) substrate group. However, there were no differences between horizontal and sloping substrate groups regarding final length, final weight, specific growth rate (SGR), and survival rate except food conversion ratio (FCR). The overall results suggested that modification of net cage nursery structure of M. rosenbergii might have significant effects on growth and survival of post-larvae by the manipulation of their behaviour in culture system. Ann. Bangladesh Agric. (2020) 24(2) : 95-106

Growth and immune response of pond-reared giant freshwater prawn Macrobrachium rosenbergii post larvae fed diets containing Chlorella vulgaris

A 70-day feeding trial was conducted to evaluate the efficacy of Chlorella vulgaris supplementation in diets of giant freshwater prawn (Macrobrachium rosenbergii) post larvae. Resistance of the prawns against Aeromonas hydrophila and several immune parameters (total hemocyte count and prophenoloxidase activity) were also assessed in the study. Iso-nitrogenous, iso-lipidic, and iso-caloric prawn feeds were prepared utilizing a fishmeal based positive control diet (F0) and four dietary treatments with C. vulgaris inclusion levels of 2 (F2), 4 (F4), 6 (F6), and 8 (F8) %. Post larvae of M. rosenbergii were stocked randomly (mean initial body weight of 0.39 ± 0.38 g) in fifteen net cages (8.1 m × 8.9 m with an average depth of 1 m) in an earthen pond for the assessment of growth parameters. Overall growth indices for prawn fed Chlorella containing diets were enhanced in comparison to the control treatment. Prawn fed diets with Chlorella showed significantly higher (P < 0.05) prophenol oxidase activity, total hemocyte counts, and survival rates post bacterial infection. These findings demonstrated that inclusion of 4%, 6%, and 8% C. vulgaris in prawn diets provided optimal growth rates and improved immunity of the post larvae.

Dietary effects of Azolla pinnata combined with exogenous digestive enzyme (Digestin™) on growth and nutrients utilization of freshwater prawn, Macrobrachium rosenbergii (de Man 1879)

The present study was conducted to evaluate the effect of either individual or combined wheat bran (WB) replacement with Azolla pinnata supplemented with Digestin™ in the diet of freshwater prawn, Macrobrachium rosenbergii Postlarvae (PL) on growth performance, nutrient utilization, chemical body composition and survival (%). Experimental diets were a wheat bran-soybean based diet with no Azolla and Digestin TM (control, T 1), and diets containing 17% Azolla supplemented with Digestin TM 0% (T2), 1% (T3), 2% (T4) and 3% (T 5). Each experimental diet was allocated into three tanks (6 m3 /tank) fed for 12 wks. Each tank was subdivided into three equal pens by nets (2 m3) and stoked with 84 PL/m2. The experimental diets were readily consumed by prawns PLs where both high growth and good feed efficiency were achieved for all diets. The results showed that the diets containing A. pinnata supplemented with Digestin™ at the level up to 3% have the higher growth and better nutrient utilization than the control diet. No differences were observed for moisture and protein content among the experimental diets. However, the highest protein content was observed on prawns fed on diets T 1 and T 5 respectively, while the lowest value was recorded for T 4 diet. The results also show that prawn PLs fed the diets contain A. pinnata and supplemented with Digestin TM recorded the highest values of body lipid content compared to the control diet. Feed efficiency and economic conversion rate (ECR) values show that economic performance and the cost-effectiveness of the A. pinnata supplemented with up to 3% Digestin TM recorded the highest net return, and therefore it is recommended for prawn, M. rosenbergii PL’s. These results are clearly indicating that A. pinnata have a good potential for use in prawn diets at reasonable levels than other conventional diets.

Green Synthesis of Chromium Nanoparticles and Their Effects on the Growth of the Prawn Macrobrachium rosenbergii Post-larvae.

This study deals with synthesis of chromium nanoparticles (CrNPs) from potassium dichromate using the aqueous extract of Allium sativum. They were characterized through UV-VIS light, FE-SEM, EDX, XRD, and FT-IR, which revealed uniform, mono-dispersive, and highly stable CrNPs of 31-64-nm size. The Artemia nauplii was enriched with 4.94mg/L of CrNPs (24-h LC50) at different durations (½, 1, 2, and 4h) and then fed to Macrobrachium rosenbegii post-larvae (PL) for 30days as live feed. The results showed that ½- and 1-h enriched Artemia nauplii led to significant improvements in nutritional indices including growth and survival, and concentrations of tissue biochemical constituents, such as total protein, amino acid, carbohydrate, and lipid of M. rosenbergii PL (P < 0.05), which suggests that this concentration of CrNPs was non-toxic to M. rosenbergii PL. This was confirmed by the insignificant alterations recorded in activities of SOD and CAT (P > 0.05) in M. rosenbergii PL fed with ½- and 1-h enriched Artemia nauplii as live feed. After that, SOD and CAT activities started to increase. Therefore, this optimized concentration of CrNPs (4.94mg/L) is recommended for enrichment of Artemia nauplii for ½-1-h duration as a sustainable material in the nursery of M. rosenbergii.

Growth Promoting Potential and Colonization Ability of Probiotics (Bacillus coagulans and Bacillus subtilis) on the Freshwater Prawn Macrobrachium rosenbergii Post-Larvae

Growth Promoting Potential and Colonization Ability of Probiotics (Bacillus coagulans and Bacillus subtilis) on the Freshwater Prawn Macrobrachium rosenbergii Post-Larvae

Low pH Water Impairs the Tactile Sense of the Postlarvae of the Giant Freshwater Prawn Macrobrachium rosenbergii.

The effect of low pH on the tactile sense of Macrobrachium rosenbergii postlarvae was determined in the laboratory by means of two behavioural assays: shelter (netting) occupancy and jumping response to touch stimuli (taps) by a glass micropipette. The postlarvae were acclimated to pH 4, pH 5, pH 6 and pH 7.5 (control) in 45 L aquaria 5–7 d before the experiments. Shelter occupancy decreased with pH and was significantly lower at pH 4 and pH 5 than at pH 6 and in the control. The jumping response instantly followed a tap 93–98% of the time in the control, pH 6 and pH 5 treatments. However, the postlarvae showed significantly lower jumping response (65%) at pH 4, indicating an impaired tactile sense. Low pH 4–5 probably degrades the chitin of the sensory setae and inhibits the surface mechanoreceptors of the prawn postlarvae.

Effects of alkalinity and total hardness on growth and survival of postlarvae freshwater prawns, Macrobrachium rosenbergii (De Man 1879)

Survival and growth of postlarvae (PL) of Macrobrachium rosenbergii (De Man 1879) were investigated under different alkalinity (25 to 500mg·L−1 and total hardness (25 to 1000mg·L−1). 45days old PL feed with a rich protein diet (38%) comprising mussels, green beans and commercial shrimp pellets, where individually held in deionised water flow through systems with chemicals added according to the HMSO (1969) formula to make up the required calcium and carbonate concentrations. Increasing alkalinity reduced the growth rate and survival of PL of M. rosenbergii. An alkalinity concentration of 250mg·L−1 or above was lethal for PL of the species as total harness increased. Total hardness as high as 1000mg·L−1 however, did not have a significant effect in the growth rate or survival as long as the alkalinity was 100mg·L−1 or lower. Thus suggesting that water with high hardness and low alkalinity in different countries could be used for the production of the species. Statement of relevanceWater suitability for the production of freshwater prawnCalcareous exoskeleton in crustaceans provides protection and support, but also imposes severe limitations, since growth is only possible by moulting. Total hardness and alkalinity of the water are important considerations in the culture of Macrobrachium rosenbergii, since they represent the concentrations of cations (calcium-magnesium) and anions (carbonates), necessary for the mineralization of the exoskeleton. M. rosenbergii has a wide range of tolerance to most of the critical parameters in aquaculture. However, the optimum levels of combinations of both alkalinity and total hardness factors for the species are yet to be fully identified. Therefore, the chemical composition of the different water bodies, and their variations, demonstrate that site selection is of paramount importance for the culture of crustaceans, depending on their requirements for alkalinity and total hardness, and the aim of this study was to investigate the effects of environmental alkalinity and total hardness in the development of PL of M. rosenbergii, as well as to identify the maximum tolerance limits and the optimum range of levels of both factors, individually and as a synergistic effect for the prawns. It was found that alkalinity levels of 250mgL−1 as CaCO3 were lethal for the species and that PL of the species could grow and survive at total hardness levels of 1000mgL−1 as CaCO3 as long as the alkalinity was lower than 100mgL−1 as CaCO3.

Dietary Supplementation of Magnesium Oxide (MgO) Nanoparticles for Better Survival and Growth of the Freshwater Prawn Macrobrachium rosenbergii Post-larvae.

This study was performed to assess the growth-promoting potential of dietary magnesium oxide nanoparticles (MgO NPs) in Macrobrachium rosenbergii post-larvae (PL). MgO NPs were supplemented at 0, 100, 200, 300, 400 and 500mgkg-1 with the basal diet (containing 0.95gMgkg-1); the concentrations of Mg in MgO NP-supplemented diets were increased correspondingly (1.07, 1.15, 1.24, 1.37 and 1.46gMgkg-1 respectively). MgO NP-supplemented diets were fed to M. rosenbergii PL (initial weight 0.11±0.04g) for a period of 90days. In the carcasses of experimental prawns, the content of Mg was found to be elevated significantly with respect to the individual diet (102.14, 183.29, 205.46, 221.03, 237.10 and 254.36μgMgg-1 respectively) when compared with that of the control. The contents of Cu, Zn, Fe, Ca, Na and K levels were also found to be elevated in the carcasses of experimental prawns. Significant (P<0.05) improvements were observed in nutritional indices [survival rate (SR), weight gain (WG), specific growth rate (SGR), feed conversion ratio (FCR) and protein efficiency ratio (PER)], activities of digestive enzymes (protease, amylase and lipase), concentrations of basic biochemical constituents (total protein, amino acid, carbohydrate, lipid, profiles of amino acids and fatty acids) and population of haemocytes [total and differential (hyalinocytes, semigranulocytes and granulocytes)] in all the test PL. Maximum performance was recorded in 500mgkg-1 MgO NP-supplemented-feed-fed PL. There were no significant elevations recorded in activities of antioxidant enzymes [superoxide dismutase (SOD) and catalase (CAT)], lipid peroxidation (LPO) and metabolic enzymes [glutamic oxaloacetic transaminase (GOT) and glutamic pyruvic transaminase (GPT)] recorded in any of the MgO NP-supplemented-feed-fed PL when compared with the control. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) showed increases in the staining intensity of polypeptide bands resolved in 500mgkg-1 MgO NP-supplemented-feed-fed PL when compared with the control. Based on the gradual improvement in attaining survival, growth, FCR, biochemical constituents and haemocyte population, this study recommends MgO NP supplementation of 500mgkg-1 for sustainable maintenance of M. rosenbergii PL. As the studied highest concentration of MgO NPs showed the best performance, it is necessary to study with beyond 500mgkg-1 of MgO NPs to optimize the actual concentration.

Identification of bacterial agents causing mortality in postlarvae of giant freshwater prawn (Macrobrachium rosenbergii ) in south-west coastal districts of Bangladesh

Following an incidence of freshwater prawn Macrobrachium rosenbergii postlarvae (PL) mortality in hatcheries in summer 2012, samples from dead PL, rearing water and prawn feed from two south-west coastal districts of Bangladesh were collected to isolate, identify and characterize the agents causing PL mortality. Antibiogram profile of sixteen randomly selected bacteria, isolated from dead PL, that grew on TCBS, to 20 different antibiotics belonging to 12 major groups revealed that the drug resistance pattern varied from moderate (56% to the drugs: ciprofloxacin, cefotaxime, nitrofurantoin, kanamycin) to complete (to penicillin, ceftazidime and oxacillin) level. To identify the isolates, amplified rDNA restriction analysis (ARDRA) classified them in to four groups, and RAPD (randomly amplified polymorphic DNA) typing yielded nine different types of isolates within these four ARDRA groups. The 16S rDNA gene sequences identified that the groups were genotypically diverse belonging to the bacterial species: Enterobacter cloacae, Klebsiella pneumoniae, Exiguobacterium profundum and Enterococcus casseliflavus, respectively, that all demonstrated their killing potential to PLs in a simulated environment. The study therefore identified four different bacterial pathogens, one of which, Exiguobacterium profundum is reported for the first here in Bangladesh, that demand special consideration for disease management strategy.

Comparative transcriptomic profiling of larvae and post-larvae of Macrobrachium rosenbergii in response to metamorphosis and salinity exposure

The high-throughput sequencing technology provides a platform for revealing the expressed genes within a tissue at a specific time. The giant freshwater prawn, Macrobrachium rosenbergii, is an economically important species, which is surviving in a wide-range of salinity. In this study, to understand the physiological mechanism of adaptability with respect to moulting and salinity; transcriptome sequencing of larvae and post-larvae of M. rosenbergii was performed using the Illumina GAIIx platform. The generated raw read-data comprised 71,391,946 and 75,276,622 paired-end reads (PE) for larvae and post-larvae respectively. Using CLC bio Genomic Workbench version 7.5 (CGWB), 71.39 million and 75.27 million of each 72 base paired-end, high quality reads were assembled into 43,383 (N50 1852) and 44,960 (N50 1874) transcripts, respectively, for larvae and post-larvae. The nucleotide level annotation of both transcriptomes showed significant similarity with unigenes of closely related species. The Gene Ontology analysis suggested enrichment of transcripts involving several biological processes linked to transcriptional regulation, signal transduction, immune response, ion-binding. Differential gene expression analysis using CGWB and DESeq identified 9680 deregulated genes of which 3454 unigenes were up-regulated and 3068 down-regulated by ≥1.5 fold (p < 0.05) in larval stage compared to post-larval stage. However, in larval stage 938 genes were down regulated and 1599 genes up-regulated by ≥3 fold with p < 0.05. GO enrichment of differentially expressed genes was shown several molecular functions for maintaining homeostasis against salinity stress. To validate the expression patterns, few transcripts were chosen for quantitative real-time PCR that showed the consistency and exactness of our analysis. In addition, we also speculated the enzymatic pathway using KEGG, which depicted that up-regulated genes are involved in several significant metabolic pathways and those are critical for maintaining osmoregulation and linked with metamorphosis. Therefore, we have generated valuable information of salinity tolerant genes in the larval and post larval stage of M. rosenbergii during salt- and freshwater compliances, which will be further harnessed for gene targeting. The present finding would provide the basis for further screening of salt tolerant genes associated markers for selective breeding.

Growth and immune response of giant freshwater prawn Macrobrachium rosenbergii (De Man) postlarvae fed diets containing Chlorella vulgaris (Beijerinck)

A 50-day growth trial was conducted to evaluate the efficacy of Chlorella vulgaris (Beijerinck) as an ingredient in the diets of giant freshwater prawn Macrobrachium rosenbergii (De Man) postlarvae (PL30). Immune response (total haemocyte count and prophenoloxidase activity) was also assessed by subjecting postlarvae to a challenge test against Aeromonas hydrophila (Chester) for 14 days. Iso-nitrogenous and iso-lipidic test diets were prepared using a fishmeal-based-positive control diet (D0) and four basal diets with inclusion levels of 2% (D2), 4% (D4), 6% (D6) and 8% (D8) C. vulgaris. Postlarvae of M. rosenbergii were randomly stocked (mean initial body weight of 0.19 ± 0.02 g) in 30-L tanks in three replicates per dietary treatment for evaluation of growth performance. Another set of postlarvae (mean initial body weight of 1.25 ± 0.02 g) was randomly distributed in 95-L tanks in three replicates per dietary treatment for the assessment of immune response. Results showed that specific growth rate was significantly higher (P < 0.05) in postlarvae fed D4 and D6. Variations in values for carcass protein, lipid, moisture and ash were also evident. Postlarvae fed diets with Chlorella showed increased prophenol oxidase activity and total haemocyte counts. Moreover, survival rate after challenge with A. hydrophila was significantly increased (P < 0.05). Inclusion of C. vulgaris in diets enhanced immune response and resistance of M. rosenbergii postlarvae against A. hydrophila infection.

Phytochemical Characterization of Couch Grass (Cynodon dactylon) and Its Growth Promoting Potential on the Freshwater Prawn Macrobrachium rosenbergii Post-Larvae

Phytochemical Characterization of Couch Grass (Cynodon dactylon) and Its Growth Promoting Potential on the Freshwater Prawn Macrobrachium rosenbergii Post-Larvae