Juvenile Prawns Research Articles

Apparent Digestibility Coefficients of Nutrients and Energy from Animal-Origin Proteins for Macrobrachium rosenbergii Juveniles

In prawn farming, the main protein source used in aquafeed formulations is fishmeal. Nevertheless, one estimates that in the coming years, this protein source will no longer be able to meet the demand for the activity. The search for new ingredients is important to meet the increasing demand and minimize environmental impacts, such as the reduction in fish stocks and the eutrophication of aquatic systems. The objective of this study was to determine the apparent digestibility coefficients of dry matter (DM), crude protein (CP), gross energy (GE), and ether extract (EE) of fishmeal, poultry co-products (viscera and hydrolysed feather), and insect meal (Gromphadorhina portentosa) for giant river prawn (Macrobrachium rosenbergii) juveniles. To determine the apparent digestibility coefficients (ADCs), 90 prawns (average weight, 15 g) were randomly distributed among three experimental units. The reference feed was formulated according to the requirements of the giant river prawn, with 35% crude protein and a gross energy of 3600 kcal kg−1. The test diets comprised 70% of the reference diet and 30% of the respective test ingredients. Prawns were fed three times a day until apparent satiety. Faeces were collected using the indirect siphoning method, twice a day at the same feeding site (at 7:30 a.m. and 6:30 p.m.). The water parameters were temperature (27 °C), dissolved oxygen (6.65 mg L−1) and pH (7.76). The ACDs of DM, CP, EE, and GE were, respectively, 61.48; 88.28; 99.89 and 88.25 for fishmeal; 76.48; 81.55; 97.29 and 85.13 for poultry viscera meal; 73.82; 75.21; 73.17 and 76.42 for hydrolysed feather meal; and 52.35; 59,48; 87.95 and 67.64 for G. portentosa meal. The values of protein (%) and digestible energy (kcal kg−1) were 55.20 and 3711 for fishmeal; 47.27 and 4285 for poultry viscera’s meal; 65.03 and 4145 for hydrolysed feather meal; and 47.72 and 3616 for G. portentosa meal. These results showed the potential use of insect meals and poultry co-products as ingredients for the diets of M. rosenbergii juveniles, as they present digestible values close to those found for fishmeal, the main raw material used in aquaculture diets.

Food and Feeding Habits of Gerres filamentosus in the Cochin Backwaters

A total of 601 specimens of Gerres filamentosus were collected from the sampling sites and were subjected to gut content analysis. Guts were visually classified according to the fullness of the stomach. Occurrence, gravimetric and volumetric methods were followed to quantify the gut contents. Feeding intensity was assessed using methods such as the Gastro rosomatic index, mean index of feeding intensity, and index of fullness. Sex wise, month and length group-wise fluctuations in the feeding intensity were also studied. It can be seen that the percentage of actively feeding fish was observed to be high during pre-monsoon and monsoon months. Feeding intensity was at its peak during April and July 2019, and the main food was found to be prawn juveniles, polychaete worms and other detritus matter.

Dietary postbiotics supplementation improves growth, survival rate, antioxidant capacity, non-specific immunity and gut health of juvenile oriental river prawn (Macrobrachium nipponense)

Antibiotics use in aquaculture cause multiple adverse effects on aquatic animal health. Accordingly, studies on alternative approaches to antibiotics in aquaculture are urgently required. This study investigated the effects of dietary postbiotics as an alternative to florfenicol antibiotic on growth performance, survival rate, antioxidant capacity, non-specific immunity, and gut health of juvenile oriental river prawn (Macrobrachium nipponense). Seven isonitrogenous and isocaloric experimental diets were formulated containing 0% (control), 0.25%, 0.5%, 1%, 2% and 4% postbiotics. These experimental diets were fed to three replicates of 70 juvenile prawns (initial weight 0.110 ± 0.010 g) for eight weeks. In addition, a diet containing 0.2% florfenicol (FFC0.2) was included as the antibiotic treatment, which was fed to the prawns for two weeks. Results showed that feeding the prawns on the postbiotics diets improved weight gain and survival rate. The prawns fed on the antibiotics or postbiotics diets increased antioxidant capacity in the hepatopancreas. Moreover, the prawns fed on the postbiotics diets increased significantly non-specific immunity. The optimum amount of postbiotics required for maximum non-specific immunity was 0.76%, 0.86% and 2.85% based on acid phosphatase, alkaline phosphatase and phenoloxidase activities, respectively. The prawns fed on the postbiotics diets upregulated significantly the mRNA expression of immunity related genes, which were downregulated significantly in the prawns fed on the FFC0.2 diet. Furthemore, the prawns fed on the 1% and 2% postbiotics diets had longer microvilli with closely packed intestinal epithelial cell and basement membrane. In summary, supplementing 0.76 to 2.66% postbiotics in the diets for M. nipponense improves growth performance, survival rate, antioxidant capacity, non-specific immunity and gut health compared with florfenicol antibiotic.

Nursery-Rearing Trials of Giant Freshwater Prawn, <i>Macrobrachium rosenbergii</i>, in Earthen Ponds

Nursery-rearing trials of the giant freshwater prawn Macrobrachium rosenbergii were carried out in five newly-excavated earthen ponds of 400 m2 each wit stocking densities ranging from 16 to 28/m2. The prawns were fed daily with pelleted feed (30% crude protein) at 10% body weight. The juvenile prawns reached an average weight of 0.655 - 1.290 g after 46-50 days of rearing. The individual daily weight increments varied from 12.8 to 23.6 mg in different trials. Per cent survival in different ponds ranged from 52.80 to 85.20 with an average of 68.79.

Isolation and characterization of a lectin-like chitinase from the hepatopancreas of freshwater prawn, Macrobrachium rosenbergii

A lectin was isolated from the hepatopancreas of freshwater prawn, Macrobrachium rosenbergii by affinity chromatography using mucin-sepharose matrix. The purity of the isolated lectin was confirmed in native gradient PAGE that showed a single protein band of ∼37.9 kDa. In SDS-PAGE also one band of ∼43.3 kDa molecular weight was observed that indicated the protein to be a monomer. The band from the SDS-PAGE gel was identified through mass spectrometry as chitinase 1. The purified chitinase (50 μg/ml) hemagglutinated rabbit RBCs and, mucin and glucose inhibited hemagglutination with minimum concentrations of 0.1 mg/ml and 100 mM, respectively. Bacterial agglutination with Gram –ve Vibrio harveyi, Aeromonas sobria and Escherichia coli was also observed by this protein. Thus, chitinase 1 showed lectin-like properties besides its chitin hydrolytic activity. In western blot with hepatopancreas sample, rabbit antiserum against chitinase 1 cross-reacted to two additional proteins namely, chitinase 1C and obstructor E (a chitin-binding protein, CBP), besides its specific reactivity. An indirect ELISA was developed with the antiserum to quantify chitinases/CBP in hepatopancreas and serum samples of M. rosenbergii. The assay was used in samples from juvenile prawns following V. harveyi challenge. At 72 h post-challenge, significantly higher levels of chitinases/CBP were quantified in the hepatopancreas of the challenged group (1.8 ± 0.2 mg/g tissue) compared to the control (1.2 ± 0.1 mg/g tissue). This study suggests that the chitinase 1 protein with lectin-like properties is possibly induced at the protein level and can be putatively involved in the innate immune response of M. rosenbergii.

Dual roles of crustacean female sex hormone during juvenile stage in the kuruma prawn Marsupenaeus japonicus

The crustacean female sex hormone (CFSH) has been identified as a female-specific hormone that plays a crucial role in female phenotype developments in the blue crab Callinectes sapidus. To date, its homologous genes have been reported in various decapod species. Additionally, unlike the blue crab, several species have two different CFSH subtypes. The kuruma prawn Marsupenaeus japonicus is a representative example species of this phenomenon, having two CFSH subtypes identified from the eyestalk (MajCFSH) and ovary (MajCFSH-ov). Eyestalk-type MajCFSH is expressed predominantly in the eyestalk at the same level in both sexes, indicating no female-specificity. Here, we conducted gene knockdown analysis of eyestalk-type MajCFSH using sexually immature juveniles of kuruma prawn (average body length: ∼10 mm) to elucidate its physiological functions. As a result, MajCFSH-knockdown did not affect the development of sex-specific characteristics such as external reproductive organs, while it induced apparent growth suppression in male juveniles, implying that MajCFSH may play a male-biased juvenile growth role. Moreover, MajCFSH-knockdown female and male juveniles changed their body color to become brighter, indicating that MajCFSH has the ability to change body color by dispersing the pigment granules in the chromatophore. Overall, our present study improved our understanding of the physiological roles of CFSH using kuruma prawn.

Effects of dietary soluble β-1,3-glucan on the growth performance, antioxidant status, and immune response of the river prawn (Macrobrachium nipponense).

The effects of dietary β-1,3-glucan on the growth performance, body composition, hepatopancreas tissue structure, antioxidant activities, and immune response of the river prawn (Macrobrachium nipponense) were investigated. In total, 900 juvenile prawns were fed one of five diets with different contents of β-1,3-glucan (0%, 0.1%, 0.2%, and 1.0%) or 0.2% curdlan for 6 weeks. The growth rate, weight gain rate, specific growth rate, specific weight gain rate, condition factor, and hepatosomatic index of juvenile prawns fed 0.2% β-1,3-glucan were significantly higher than those fed 0% β-1,3-glucan and 0.2% curdlan (p < 0.05). The whole-body crude lipid content of prawns supplemented with curdlan and β-1,3-glucan was significantly higher than that of the control group (p < 0.05). The antioxidant and immune enzyme activities of superoxide dismutase (SOD), total antioxidant capacity (T-AOC), catalase (CAT), lysozyme (LZM), phenoloxidase (PO), acid phosphatase (ACP), and alkaline phosphatase (AKP) in the hepatopancreas of juvenile prawns fed 0.2% β-1,3-glucan were significantly higher than those of the control and 0.2% curdlan groups (p < 0.05), and tended to increase and then decrease with increasing dietary β-1,3-glucan. The highest malondialdehyde (MDA) content was observed in juvenile prawns without β-1,3-glucan supplementation. The results of real-time quantitative PCR indicated that dietary β-1,3-glucan promoted expression of antioxidant and immune-related genes. Binomial fit analysis of weight gain rate and specific weight gain rate showed that the optimum β-1,3-glucan requirement of juvenile prawns was 0.550%-0.553%. We found that suitable dietary β-1,3-glucan improved juvenile prawns growth performance, antioxidant capacity, and non-specific immunity, which provide reference for shrimp healthy culture.

Molecular characterization and transcriptional response to TiO2–GO nanomaterial exposure of two molt-related genes in the juvenile prawn, Macrobrachium rosenbergii

In recent years, with the widespread use of TiO2–GO nanocomposite in industry, especially in the remediation of water environments, its toxic effects on aquatic organisms have received increasing attention. As molting is extremely important for crustaceans in their growth, in this study, we cloned the full-length cDNA sequences of two key genes related to molting, nuclear hormone receptor E75 (E75) and nuclear hormone receptor HR3 (HR3), in Macrobrachium rosenbergii, examined the gene expression profile, and investigated their toxicological effects on crustacean molting through nanomaterial exposure. The amino acid sequences for E75 and HR3 were respectively determined to encode 1138 and 363 acid residues. Sequence analysis showed that both E75 and HR3 contain a HOLI domain, with the E75 of M. rosenbergii being more closely related to the E75 of Palaemon carinicauda. These two genes were expressed at the highest levels in muscle, followed by hepatopancreas. The results showed that the expressions of E75 and HR3 in hepatopancreas and muscle tissues were significantly decreased after exposure to 0.1 mg/L of TiO2–GO composite nanoparticles (P < 0.05). This study will serve as a foundation for subsequent research into the evaluation of nanomaterial toxicity on crustacean species.

Two genes related to apoptosis in the hepatopancreas of juvenile prawn, Macrobrachium nipponense: Molecular characterization and transcriptional response to nanoplastic exposure

Nanoplastics have been widely found in the global water environment, causing plastic pollution and affecting human beings and numerous organisms. Studies involving freshwater crustacean exposure to nanoplastics, however, are limited. In this study, juvenile prawns (Macrobrachium nipponense) were exposed to 75 nm polystyrene nanoplastics at different concentrations (0, 5, 10, 20, or 40 mg/L) for a 28-d chronic exposure experiment. To study the effects of exposure to nanoplastics on hepatopancreas cell apoptosis, C-Jun N-terminal kinase (JNK) and phosphatidylinositol-4,5-bisphosphate 3-kinase, catalytic subunit alpha (PIK3CA) genes were selected, and hepatotoxic enzyme activities and Toll pathway- and apoptosis-related gene expression were determined. For the first time, full-length Mn-JNK and Mn-PIK3CA cDNAs were cloned from M. nipponense. Homologous comparisons showed that JNK and PIK3CA had conserved functional sequences. The apoptosis rate in the high-concentration nanoplastic group (40 mg/L) was significantly higher than in the low-concentration nanoplastic (5 mg/L) and control groups (0 mg/L). The alanine aminotransferase (ALT), aspartate aminotransferase (AST), glutamyl transpeptidase (GGT) and xanthine oxidase (XOD) enzyme activities in the hepatopancreas increased with exposure to higher concentrations of nanoplastics. In addition, the levels of apoptosis- and Toll pathway-related gene expression and JNK and PIK3CA gene expression were initially increased, then decreased with exposure to higher concentrations of nanoplastics. This study showed that polystyrene nanoplastics activate toll-related pathways leading to apoptosis and hepatopancreas damage, which provides theoretical support for future aquatic toxicological research.

Impact of Titanium Dioxide-Graphene Oxide (TiO2-GO) Composite Nanoparticle on the Juveniles of the Giant River Prawn, Macrobrachium rosenbergii: Physio-Biochemistry and Transcriptional Response

Nanomaterials are used in many fields, resulting in inevitably releasing into the aquatic environment. The presence of nanomaterials, including TiO2-GO in the aquatic environment, can be toxic to aquatic organisms. However, few studies have focused on the effects of TiO2-GO composite nanoparticle on crustaceans. In the present study, the giant river prawn Macrobrachium rosenbergii juveniles were exposed to two concentrations of TiO2-GO composite nanoparticle (0.1 and 0.5mg/L). The effects of TiO2-GO composite exposure on activities of digestive and antioxidant-related enzymes and expressions of growth and immune-related genes at the transcriptome were studied. The results showed that the survival rate and growth performance were not negatively affected by TiO2-GO composite at the two exposure levels. Nevertheless, exposure to TiO2-GO composite causes an effect on the activities of digestive and antioxidant enzymes in the juvenile prawns. The enzyme activities of CAT, SOD, GSH-Px, AMS, TPS, and LPS in the 0.1mg/L TiO2-GO composite experimental group were markedly reduced than those in the control group. Additionally, the expression level of genes involved in growth and immunity was significantly affected by TiO2-GO composite. After exposure to the 0.1mg/L TiO2-GO composite, the mRNA expression level of MSTN was significantly increased, but the level of EcR, Raptor, and CaBP was significantly decreased. However, the mRNA levels of the CTL, TLR, JAK, and STAT were significantly increased after exposure to the 0.5mg/L concentration of TiO2-GO composite. Furthermore, to understand the molecular mechanism of M. rosenbergii under TiO2-GO composite exposure, RNA-Seq was employed to analyze the changes of the muscle and hepatopancreas transcriptome. Compared with the control group, we identified 5166 and 4784 differentially expressed genes (DEGs) in the muscle and hepatopancreas, respectively (p < 0.05). Based on gene ontology and KEGG analysis, significant differences were observed in the DEGs involved in activity and binding, metabolism, immune response, and environmental information processing. These results showed that exposure to TiO2-GO composite nanoparticle led to the changes of enzyme activity and gene expression, suggesting that TiO2-GO composite existing in aquatic environments would disrupt the physiology of M. rosenbergii. This study will serve as a foundation for subsequent research into the evaluation of nanomaterial toxicity on crustacean species.

Effects of salinity and alkalinity on growth and survival of all-male giant freshwater prawn (Macrobrachium rosenbergii De Man, 1879) juveniles

All-male giant freshwater prawns (AMGFPs) have been a popular crop cultivated in the Mekong Delta, Vietnam, due to their proven production efficiency compared to all-female or mixed-sex prawn cultures. However, the crucial water quality factors impacting AMGFP aquaculture efficiency have yet to be elaborately investigated. Two separate experiments were randomly arranged with three replicates to evaluate the effects of salinity or alkalinity on the growth and survival of AMGFP juveniles during the grow-out period. The results show that the prawn survival rate in the salinity range of 0–15‰ varied from 66.1 to 74.8％ and in a salinity range of 0–5‰ was relatively low compared to the range of 10-15‰; however, the difference was not significant among salinities after 90 days of culture (p &gt; 0.05). All the prawn growth performance parameters significantly decreased with increasing salinities of 0, 5, 10, and 15‰ after 30, 60, and 90 days of culture (p &lt; 0.05). Notably, the prawn yield did not significantly differ between salinities of 0 and 5‰ (p &gt; 0.05), and both were significantly higher than those at salinities of 10 and 15‰ (p &lt; 0.05) after 90 days of culture. In addition, the survival rate reached 82.5–84.4％ and did not significantly differ among alkalinities of 80, 100, 120, 140, and 160 mgCaCO3 L−1. However, the growth performance parameters and yield of AMGFPs at an alkalinity of 160 mg L−1 were significantly higher than those at lower alkalinities (80, 100, 120, and 140 mg CaCO3 L−1) after 90 days of culture. Therefore, it is recommended that a salinity range of 0–5‰ and alkalinity of 160 mgCaCO3 L−1 is optimal for the growth-out culture of AMGFP juveniles.

Effects of dietary threonine on growth and immune response of oriental river prawn (Macrobrachium nipponense)

A 70-day feeding trial was conducted to ascertain the effects of threonine on immune response of juvenile oriental river prawn (Macrobrachium nipponense). Six isonitrogen and isolipidic feeds were formulated according to levels of dietary threonine (0.35%, 0.79%, 1.18%, 1.67%, 2.08% and 2.48% respectively). The juvenile prawns were divided into six groups with four replicates, and stocked into 24 tanks with 50 prawns per tank (initial weight 0.20 ± 0.02 g). The results showed a significant increasing trend of final body weight, specific growth rate, protein efficiency ratio, and weight gain rate when threonine levels increased to 1.67% (P < 0.05). However, feed intake, feed conversion ratio, and whole-body lipid composition significantly decreased as threonine levels in the feed increased up to 1.67% (P < 0.05). Moreover, haemolymph N-urea content was significantly lowest at 1.67% threonine level (P < 0.05), whereas glucose was highest at 0.79% followed by 1.67% of threonine levels in the feeds. Aspartate aminotransferase (AST) enzyme activities were significantly decreased by an imbalance (except 1.67%) of threonine in the feed (P < 0.05). Activities of Alanine aminotransferase (ALT) and albumen (ALB) were not significantly affected by threonine in the feed (P > 0.05). Excessive dietary threonine level (2.48%) significantly activated haemolymph catalase (CAT) activity (P < 0.05), whereas malondialdehyde (MDA) content was significantly affected by deficient (0.35% and 0.79%) dietary threonine levels (P < 0.05). Inducible nitric oxide synthase (iNOS) activity and haemolymph complement component 4 (C4) content were significantly decreased by deficient levels of threonine in the feed (P < 0.05). Excess threonine concentration significantly down-regulated Toll, Dorsal, Relish, and heat shock protein 60 (Hsp60) gene expressions in the hepatopancreas of M. nipponense (P < 0.05), while all genes were significantly up-regulated by the optimal (1.67%) threonine level (P < 0.05). The threonine level at which maximum specific growth rate of M. nipponense occurred was estimated by second degree polynomial regression analysis as 1.65% of threonine level, equivalent to 4.44% dry weight bases of protein in the feed.

Dietary magnesium improves the growth, antioxidant capacity, ammonia nitrogen tolerance and intestinal health of juvenile oriental river prawn Macrobrachium nipponense

The present study evaluated the effects of magnesium (Mg) on growth, antioxidant capacity, intestinal morphology and ammonia nitrogen resistance in juvenile oriental river prawn, Macrobrachium nipponense. Six semipurified diets (crude protein 401.1 g kg−1 diet; crude lipid 88.7 g kg−1 diet) containing Mg levels of 1.1, 1.4, 1.6, 2.1, 2.8 or 4.5 g kg−1 were formulated. A total of 1080 healthy juvenile prawns (0.151 ± 0.003 g) were randomly stocked into eighteen 300 L tanks (100 × 80 × 60 cm), each tank with 60 prawns. Each experimental diet was fed to prawns in triplicate twice daily (08:00 and 17:00) for eight weeks. After the feeding trial, 20 prawns from each tank were challenged with 37 mg/L ammonia nitrogen for 96 h, and the hemolymph, hepatopancreas and muscle of the rest of the prawns were collected. Final biomass was higher in prawns fed diets containing 1.6 and 2.1 g Mg kg−1 compared with those fed the diet with 1.1 g kg−1. Higher alkaline phosphatase (ALP) activity was obtained in the serum of prawns fed the 2.1 and 2.8 g Mg kg−1 diets. The highest activities of hepatopancreas superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and total antioxidant capacity (T-AOC) were observed in prawns fed 1.6–2.8 g Mg kg−1 of feed, and the lowest hepatopancreas malondialdehyde (MDA) concentrations and serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activities were found in these treatment groups. Similarly, the prawns fed diets with 1.6 and 2.1 g Mg kg−1 had significantly lower MDA concentrations and cumulative mortality and higher antioxidant enzyme activities after ammonia nitrogen exposure. The intestinal epithelial cells were closely attached to the membrane in prawns fed the 2.1 g Mg kg−1 diet, but they were partly detached in those fed the 1.1 and 4.5 g Mg kg−1 diets. The minimum dietary Mg supplementations of juvenile M. nipponense were determined to be 1.6, 1.9, 2.0 and 2.2 g kg−1 feed, respectively, using broken-line regression analysis based on the final biomass, SOD, ALT and ALP.

Functional analysis of a matrix peptide involved in calcification of the exoskeleton of the kuruma prawn, Marsupenaeus japonicus

To clarify the calcification mechanism of the exoskeleton of marine crustaceans, kuruma prawns (Marsupenaeus japonicus), which are commercially important prawns in Japan, were used, and calcification-associated peptide (CAP), a matrix peptide that was previously reported in red swamp crayfish, was examined. Based on the RNA-sequencing data of kuruma prawns, a candidate Cap-1 cDNA sequence was found. Thereafter, the nucleotide sequence of kuruma prawn Cap-1 was determined by PCR methods using a specific primer set. Mature kuruma prawn CAP-1 showed a 66.7% amino acid identity with red swamp crayfish CAP-1. This sequence was presumed to be kuruma prawn CAP-1 because specific sequences, such as a chitin-binding consensus sequence, and many acidic amino acids in the C-terminal region were also observed in red swamp crayfish CAP-1. Then, a recombinant Cap-1 (rCAP-1) was expressed in Escherichia coli and purified by reverse-phase high-performance liquid chromatography. The purified rCAP-1 showed both chitin-binding and inhibitory activities of calcium carbonate precipitation. Based on Cap-1 mRNA expression analysis in the swimming legs and tail fans of juvenile prawns during molting, its mRNA expression level increased remarkably in the middle and late pre-molt stages. Cap-1-expressing cells were also identified by in situ hybridization using the swimming legs in the late pre-molt stage. It was found that kuruma prawn Cap-1 was expressed in epidermal cells under the cuticle layer. Due to knockdown using RNA interference (RNAi) methods, the Cap-1 mRNA expression in Cap-1-double-stranded RNA (dsRNA)-injected prawns decreased significantly in the middle and late pre-molt stages as compared with that in green fluorescent protein-dsRNA-injected control prawns. Furthermore, an irregularly shrunken and uneven structure appeared on the surface of the cuticle of dsRNA-Cap-1-treated prawns in the post-molt stage, and calcium deposition was inhibited by RNAi of Cap-1. Regarding marine crustaceans, to the best of our knowledge, this study is the first to determine that kuruma prawn CAP-1 has chitin-binding and anti-calcification activities and functionally changes its mRNA expression during molting. These results indicate that kuruma prawn CAP-1 plays important roles in exoskeleton calcification.

Photoprotection Effects of Red Seaweed Meal (Grateloupia cf. Turuturu) as Feed Ingredient in Prawn Artemesia Longinaris.

The aim of this research was to determine the effects of adding red seaweed meal rich in ultraviolet radiation absorbing compounds (UACs) to the diet of juvenile prawn Artemesia longinaris and its possible protective effects under stress by ultraviolet radiation (UVR). Three experimental diets were prepared: control diet (D) and two diets supplemented with red seaweed Grateloupia cf. turuturu meal at two inclusion levels (D1: 1 g/100 g; D2: 2 g/100 g). Three experiments were carried out: a) 45-day feeding, b) digestibility, and c) radiation exposure experiment. After the 45-day feeding experiment, no significant differences were found in growth and survival. Accumulation of UACs was detected only in animals fed D1 and D2, and concentration was significantly higher in animals fed D2, with concentrations (12.58 ± 3.50 OD g-1 ) and (3.17 ± 0.4 OD g-1 ) after 45-day feeding and after 7-day UVR exposure, respectively. After 7 days of exposure to different light treatments, significant differences were recorded inradical scavenging activities. In all UVR treatments, rapid signal decay was recorded in the first 5 min of reaction. The red seaweed Grateloupia cf. turuturumeal constitutes an interesting source of photoprotective compounds as an additive in the diet of A. longinaris.

Beta-Agonist, Ractopamine Hydrochloride, Improves Growth, Alters Body Composition, and Suppresses Gonadal Maturation in All-Female Giant Freshwater Prawn, Macrobrachium rosenbergii

All-female giant freshwater prawn Macrobrachium rosenbergii has a significant growth limitation due to its early sexual maturity. A 60-day trial was carried out to determine the effect of beta-agonist, ractopamine hydrochloride (RAC), on the growth performance, body composition, and gonadal maturation of all-female prawns. Prawn juveniles ( 4.39 ± 0.40 g initial weight) were stocked at 10 prawns/m2 in 15 plastic tanks (1000 liters each) in a completely randomized design with four treatments and a control (0, 5, 10, 15, and 20 mg/kg) in triplicate. The significantly ( p &lt; 0.05 ) highest values of final weight, weight gain, daily weight gain, and specific growth rate (SGR) were observed in the female prawns fed with the diet containing 10 mg/kg RAC, while the lowest values were found in the control tank. Similarly, survival rate, feed conversion rate (FCR), and condition factors were observed among all treatments, which were significantly better than the control (0 mg/kg). Significantly greater yield and lower gonadosomatic index (GSI) values were obtained in prawns fed with a 10 mg/kg RAC-containing diet than in all other treatments, except for the diet containing 15 mg/kg RAC, while the lowest yield was produced by the control tank. A diet containing 10 mg/kg RAC had significantly improved the whole-body protein content in prawns, while diets containing 10 and 15 mg/kg RAC exhibited lower lipid content in prawns than in the other treatments. A significant increase in the number of Stage 1 (virgin) females (up to 54% at 10 mg/kg RAC diet) was found in all RAC treatments, while the control had a significantly higher number of females at various maturity stages, indicating that RAC administration effectively suppresses gonadal maturity. Residue analysis of whole prawn samples at the end of the trial indicated no trace of ractopamine. The quadratic regression analysis of weight gain, SGR, FCR, and yield revealed that the optimum dietary ractopamine level for all-female prawn culture should be between 10 and 15 mg/kg.

Dichlorodiphenyltrichloroethane (DDT) residues status in fishes and prawns of Chittagong chemical complex area, Bangladesh

Fourteen various fish samples i.e., rui Labeo rohita, catla Gibelion catla, striped dwarf catfish Mystus vittatus, stinging catfish Heteropneustes fossilis, walking catfish Clarias batrachus, Ganges river sprat Corica soborna, mola carplet Amblypharyngodon mola, common carp Cyprinus carpio, Nile tilapia Oreochromis niloticus, climbing perch Anabas testudineus, spotted snakehead Channa punctatus, striped snakehead Channa striata, bronze featherback Notopterus notopterus, wallago catfish Wallago attu and mixed juvenile prawns were collected from a pond of closed down DDT (Dichlorodiphenyltrichloroethane) factory area of Chittagong Chemical Complex (CCC) of Bangladesh to assess the concentrations of DDT and its metabolites (4,4'-DDD and 4,4'-DDE). The fish flesh and shell-free prawn muscle samples were extracted by QuEChERS method and these were cleaned up using H2SO4. The cleaned sample extracts were analyzed using a Gas Chromatograph coupled with Electron Capture Detector (GC-ECD). The cultured L. rohita was used as a control which was found to contain no detectable amount of DDTs. Recovery experiments with control samples were spiked with certified DDTs standard at three different concentrations (0.01 mg kg-1, 0.02 mg kg-1 and 0.05 mg kg-1) levels. The percent recoveries were 72-114 % (0.05 mg kg-1), 70-101 % (0.01 mg kg-1) and 87-105 % (0.02 mg kg-1). LOD and LOQ of the standards were found to be 0.0625 μg kg-1 and 0.2063 μg kg-1, respectively and R2 of 4'-DDE, 4,4'-DDD, 2,4'-DDT and 4,4'-DDT were found to be 0.999, 0.999, 0.999 and 0.998, respectively. The concentrations of total DDTs residue in fish and prawn samples ranged between 0.66 ng g-1 in W. attu to 8.90 ng g-1 in H. fossilis. The ratios of 4,4'-DDT/ΣDDTs in the studied fish samples indicated the historical use of DDTs in the adjacent region around the DDT factory of the CCC area. The concentrations of total DDTs in all the samples were within the permissible Maximum Residue Level (MRL) recommended by FAO-WHO. To assess human health risks, Health risk Indexes (HI) of fish and prawn samples were calculated. HIs&lt;1 in all fish and prawn samples indicated that the fish samples are safe to consume but the daily consumption of the fish together with other contaminated food may cause human health hazards. Bangladesh J. Zool. 49 (3): 381-391, 2021

UTILIZING VILLAGE WATER BODIES FOR POLYCULTURE OF FISH AND PRAWN: ROLE OF INPUTS IN PRODUCTION ENHANCEMENT

A field study on participatory technology development (PTD) approaches was taken up in the southern transitional zone (Zone 7) of Karnataka in village water bodies leased by the Grama Panchayat. Polyculture of Indian Major Carps catla and rohu with freshwater prawn Macrobrachium rosenbergii was investigated. The experimental water bodies were of the size 0.8 to 1.0 ha, having an average depth of 1.8 m to 2 m. After observing pre-stocking management measures, the water bodies were stocked with fingerlings of catla and rohu at 0.5 /m2each and juveniles of prawn at1/m2. In T1, replicate water bodies received cow dung as manure at 6 t/ha, applied in split doses of 375 kg once every fortnight and the fish were fed at the rate of 3% of body weight daily in the morning hours. Water bodies receiving only cow dung at 6t/ha were designated T2. Two water bodies without either of the inputs served as the control and were designated as T3. The average total production in T1 treatment was significantly higher at 3401.40 kg/ha compared to T2 and T3, which recorded 1674.25 kg/ha and 975.75 kg/ha production respectively. Production of the prawn was 544.50 kg/ha, 146.75 kg/ha and 45.25 kg/ha in T1, T2, and T3 treatments. The average survival rate of fish was 83.41%, 54.39%, and 32.16%, while that of the prawn was 64.55%, 34.65% and 28.6% respectively. The study indicates that use of manure and feed in polyculture of fish and prawns could be a viable strategy for enhancing productivity and profitability in village water bodies.

Effects of dietary supplementation with 17β-estradiol and 17α-methyltestosterone on growth performance and gonadal development of the juvenile oriental river prawn (Macrobrachium nipponense)

17β-Estradiol (E2) and 17α-methyltestosterone (MT) are steroid hormones with dramatic regulatory effects on the growth performance and gonadal development of aquatic species. The aim of the present study was to investigate the regulatory effects of E2 and MT on the growth performance and gonadal development of juvenile prawns (Macrobrachium nipponense). Male and female juvenile prawns were separately maintained and fed different concentrations of E2 and MT, respectively. Treatment with both E2 and MT at 500 mg/kg dramatically promoted the growth of male and female juvenile prawns, respectively (p < 0.05). The growth rate of M. nipponense treated with E2 and MT at 1000 mg/kg at 30 days were 2.59 ± 0.31 and 2.21 ± 0.37, which were almost two- and five-fold greater than that of the control group, respectively. E2 showed better effects on the promotion of growth performance than MT. Histologically, testicular and ovarian development were delayed at E2 and MT concentrations of ≥ 500 mg/kg. Sperm had normally developed after 15 and 30 days of E2 treatment at ≤ 250 mg/kg, but were rarely observed in the testis at E2 concentrations greater than 500 mg/kg. The number of prawns at ovarian stages Ⅳ and V was increased with decreased MT concentrations. The qPCR results revealed that the expression levels of sperm gelatinase and insulin-like androgenic gland hormone were significantly decreased after E2 treatment from 100 mg/kg as compared to the control group (p < 0.05), while the expression levels at different E2 concentrations remained stable (p > 0.05). The expression levels of vitellogenin and vitellogenin receptor were dramatically decreased with increased MT concentrations, and the lowest expression levels were observed in the group treated with 1000 mg/kg (p < 0.05). Testosterone levels decreased with increased E2 concentrations (p < 0.05). In addition, lower MT concentrations (≤ 250 mg/kg) stimulated the secretion of E2 (p < 0.05), while higher concentrations (500 and 1000 mg/kg) had an opposite effect (p < 0.05). In summary, dietary supplementation with high doses of E2 and MT (500 and 1000 mg/kg) promoted the growth and inhibited gonadal development of juvenile M. nipponense. These findings provide important evidence of the effects of MT and E2 on the growth performance and gonadal development of juvenile M. nipponense, thereby establishing an artificial technique to regulate gonadal development.

Survival of the prawn Macrobrachium tenellum (Smith, 1871) in confinement with the native fish Dormitator latifrons (Richardson, 1844)

Objective: The aim of this study was to test the survival of Macrobrachium tenellum in different confinement conditions with Dormitator latifrons.&#x0D; Design/methodology/approach: Using wild specimens acclimated to captive conditions of both species, three trials of different proportion were performed with treatments consisting in the presence/absence of food and shelters. Prawn/fish proportion for the assays were: 15/15 for T1, 15/3 for T2 and 10/3 for T3. In assays T1 and T2 juvenile prawns and fish were used, while in T3 post-larvae prawns and pre-juvenile fish were used. To test the survival with or without fed, it was schedule a four-day feeding ad libitum period, following by a two-day fed depravation period in all the assays.&#x0D; Results: In assays with juveniles of M. tenellum the survival rate was superior to 80% with or without shelter, when T1 showed 97-100% survival; meanwhile T3 presented a 56.67 % of survival, suggesting it’s necessary to use only juvenile prawns in co-culture systems. The use of shelters and fed deprivation had no significant effects on the survival of prawns.&#x0D; Limitations on study/implications: M. tenellum is an important aquatic resource for the central Mexican Pacific, region in which the D. latifrons is a representative native fish with a developing aquaculture. A polyculture or co-culture system with these species can accelerate the sustainability of both species productions.&#x0D; Findings/conclusions: The results suggest this polyculture system may be feasible, and longer duration culture are recommended.