The present study was carried out to investigate the dietary effects of different levels of synthetic astaxanthin on reproductive performance of giant freshwater prawn (Macrobrachium rosenbergii). 24 broodstock prawns were randomly distributed into 3 treatments considering male to female ratio as 1: 3 in duplicates. Experimental diets were supplemented with an amount of 0 (as control), 50 and 100 mg. Kg-1 astaxanthin. Prawns were fed on experimental diets in a ratio of 2% biomass for a period of 45 days. Total carotenoid, number of eggs per gram, eggs diameter, hatching rate and number of larvae after hatching as broodstock reproductive performance indices while larval somatic index (LSI) and larval length were measured to assess larval quality. Results showed that diet supplementation with synthetic astaxanthin significantly affects the number of eggs and number of larvae after hatch (P<0. 05). Also, a significant difference was observed in total carotenoid, eggs diameter, LSI and larval length (P<0. 05). Thus, based on these results and being more costeffective 50 mg. Kg-1 supplementation level is recommended to improve giant freshwater prawn reproductive performance.

Use of effective substances to inhibit bacteria in the aquatic environment due to indiscriminate and long-term use of antibacterial substances such as antibiotics seems to be necessary. Polyethyleneimine (PEI) is a synthetic polymer with antibacterial properties and chemical formula (C2H5N)n which consists of many side groups of NH2, the use of this polymer due to its antibacterial property in binding with different substrates can be considered. Among these substrates that are widely used in aquaculture is Zeolite. In this study, zeolite was coated with PEI polymer with two concentrations of 1 and 2 mg/l and after confirmation by Fourier transform infrared spectroscopy (FTIR) analysis is placed inside the filters. The function of the filters was determined by measuring the bacterial load of the water, survival and growth of post larvae. The results showed that negative control, treatment of zeolite modified with concentration I, treatment of zeolite modified with concentration II of PEI polymer, treatment of natural zeolite and positive control at 104 CFU/ml Aeromonas hydrophila bacteria on the 10 days of the experiment were grew 50, 125, 125, 348 and 380 colony/100 ml in TSI medium, which shows a decrease of 67.1% of the bacterial load in both modified treatments with concentrations I and II of PEI polymer compared to the positive control. Also, the survival rate of postlarvae showed a significant increase in the treatment of modified zeolite with concentration I and II compared to the negative control (P<0.05). However, there was no significant difference between treatments in dry weight and length (P>0.05). Finally, after summarizing and comparing the results of this study with others, it can be concluded that the use of zeolite modified with PEI polymer in the filtration system of giant freshwater prawn Macrobrachium rosenbergii post larval rearing tanks has a potential effect on bacterial reduction of Aeromonas hydrophila bacteria.

Heavy metals are at present classified among the most important and dangerous water pollutants and are considered as the serious threat to human health. Current study has been focused on concentration of two heavy metals; Zinc and Copper in the flesh of Macrobrachium rosenbergii and to observe their induced histopathological alterations in gills and hepatopancreas. The levels of Zn and Cu in 20 giant freshwater prawn specimens from Siahrood River in Mazandaran Province, Iran, were investigated during winter 2013. The concentrations of the metals were carried out by using Atomic Absorption Spectrophotometer .The gills and hepatopancreas specimens from each prawn were sampled in order to reveal the histopathological changes. Statistical analysis was carried out by SPSS19 software. The mean concentrations of Zn and Cu in the muscle of examined prawn were 1/011±0.01 and 1.785±0.02 (mg/kg dry weight) respectively. Using one sample t-test at 95% confidence limit, there were significant difference in the levels of Zn and Cu, but there were not any significant difference in correlation between the mean concentration of Zn and Cu and the average of body lengths and weights. The data show that the concentrations of Zn and Cu in the flesh of prawn are below the legal value for aquatic products established by WHO, NHMRC and UK(MAFF), showed that the giant freshwater prawn from investigated region are safety for human consumption. In histopathological view, Edema, Inflammatory cells and epithelial hyperplasia changes of gills with lots of mucus were observed. In hepatopancreas atrophy and fatty changes were existed.

Possible effects of a synthetic juvenoid hormone (pyriproxyfen) on larval development, metamorphosis and survival of a crustacean octapod, Macrobrachium rosenbergii, was studied. Although Pyriproxifen is well known as an effective pest control product, our knowledge about its effects on crustacean metamorphosis, especially on larval stages is yet little. Macrobrachium rosenbergii is a suitable invertebrate species in the neurobiological and endocrinological researches. The species has 11 larval stages with obvious morphological features for every stage.In this study, larvae of the species were treated with 0.01, 0.05 and 0.1ppm of Pyriproxifen against a group of control for which xylene was used. In the first day of exposure to the Pyriproxifen, all larvae were in the 1st larval stage. We studied the larval stages in samples obtained in different days and percentage of survival in the end of metamorphosis for treatment and control groups. The results showed that all concentrations of Pyriproxyfen significantly caused a delayed larval development and metamorphosis. Furthermore, the post larval survival rates of all treatment groups were less than control.These results suggest that synthetic juvenoid hormone retards the larval morphological development in Macrobrachium rosenbergii, and decreases the survival of the species.

β-glucans (BG) are widely used as an immunostimulant in aquatic animals through injection, feed, and immersion. The present study aimed to examine the consequences of dietary administration of yeast β-glucan on the immune response and susceptibility of Macrobrachium rosenbergii to the Vibrio parahaemolyticus infection. Experimental prawns (4.55±0.08 g) were fed a formulated commercial diet supplemented with commercial yeast BG at 0.0% (control), 0.1% (T1), 0.2% (T2), and 0.3% (T3). After the feeding trial of 75 days, a challenge test with V. parahaemolyticus (104 cfu/mL) was performed for seven days. No significant differences (p>0.05) were observed in terms of final weight, specific growth rate, and weight gain, but the prawns fed with 0.1% (T1) BG had the highest survival rates (100%). However, immune parameters, e.g. level of total hemolymph protein, albumin, globulin and hemocyte number, were found to be significantly higher (p<0.05) in prawns fed with 0.2% (T2) BG-supplemented diet. The total hemocyte count and total hemolymph protein, albumin, and globulin were reduced after the V. parahaemolyticus infection. The study's findings suggested that yeast BG can be used at 0.1% to 0.2% to enhance the immune response of juvenile M. rosenbergii and increase their resistance to V. parahemolyticus infection without upsetting the usual growth and survival.