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The shrimp immune system defends and protects against infection by its naturally expressing antimicrobial peptides. Stylicin is a proline-rich anionic antimicrobial peptide (AMP) that exhibits potent antimicrobial activity. In this study, stylicin gene was isolated from Penaeus vannamei, cloned into vector pET-28a (+), and overexpressed in Escherichia coli SHuffle T7 cells. The protein was purified and tested for its antibiofilm activity against shrimp pathogen Vibrio parahaemolyticus. It was resulted that the recombinant stylicin significantly reduced the biofilm formation of V. parahaemolyticus at a minimum inhibitory concentration (MIC) of 200 µg. Cell aggregation was observed by using scanning electron microscopy and confocal laser scanning microscopy, and it was resulted that stylicin administration significantly affects the cell structure and biofilm density of V. parahaemolyticus. In addition, real-time PCR confirmed the downregulation (p < 0.05) of genes responsible for growth and colonization. The efficacy of stylicin was tested by injecting it into shrimp challenged with V. parahaemolyticus and 7 days after infection, stylicin-treated animals recovered and survived better in both treatments (T2—100 µg stylicin, − 68.8%; T1—50 µg stylicin, 60%) than in control (7%) (p < 0.01). Comparative proteomic and mass spectrometry analysis of shrimp hemolymph resulted that the expressed proteins were involved in cell cycle, signal transduction, immune pathways, and stress-related proteins representing infection and recovery, and were significantly different in the stylicin-treated groups. The result of this study suggests that the stylicin can naturally boost immunity and can be used as a choice for treating V. parahaemolyticus infections in shrimp. [ABSTRACT FROM AUTHOR]

With an aim to evaluate the culture potential of Indian white shrimp, Penaeus indicus grow-out farming trials were carried out under different salinity regimes and stocking densities across the coastal states of India (West Bengal, Odisha, Andhra Pradesh, Tamil Nadu, and Kerala). The growth performance and immunity status were assessed under two different stocking densities (low and high) at each salinity regime (S1: 3–7; S2: 8–15; S3:15–25; S4:25–35; and S5:40–60 ppt) for a period of 80–120 days. Significantly higher growth was observed in the salinity range of 15 to 35 ppt with average daily growth (ADG) up to 0.195 ± 0.032 compared to low ADG of 0.125 ± 0.021 in very low and very high salinity range (< 7 ppt and > 40 ppt). Similarly, the final mean harvest weight of P. indicus reared at 15–25 ppt salinity was significantly (p < 0.05) higher compared to other salinity ranges. The lower stocking density treatment ponds demonstrated higher mean harvest weight (18–30 g) with a production ranged from 2200.59 ± 331.09 kg/ha/crop to 3611.02 ± 218.23 kg/ha/crop compared to higher density ponds (12–20 g) which was ranged from 4338.67 ± 650.37 kg/ha/crop to 7817.31 ± 158.78 kg/ha/crop. The total productivity (kg/ha/crop) significantly (p < 0.05) increased with increase in stocking density by 20–30% while it was comparable between salinity ranges. The prophenoloxidase (PPO) activity gradually increased or decreased correspondingly to the salinity level with significantly lower PPO activity being observed at very low (5 ppt) and very high (60 ppt) than other salinity ranges. The serum protein and lysozyme also varied with the salinity range. Different densities did not affect immune parameters much, although lower stocking density was showing marginal increase. This study is based on large data from multi-location trials undertaken across different salinity ranges and stocking densities and provides a field-level assessment of growth potential of this native shrimp species in different geographic locations. [ABSTRACT FROM AUTHOR]

Biofloc culture system is an eco-friendly method, because it limits the water usage and effluent discharge to the surrounding environment. The present study aimed to investigate immune potential, growth, and survival of Indian white shrimp Penaeus indicus, post larvae in the biofloc technology (BFT) with C:N ratio of 15:1 during nursery phase in different salinities (5‰, 15‰, 25‰, 30‰, and 35‰). Experiments were conducted in triplicate in 100-L-reinforced fiber plastic (FRP) tanks, and P. indicus (post larvae 10) were stocked at the density of 120 numbers/tank (1.2post larvae/L). The total suspended solid (TSS) level in each biofloc group was maintained at 200–300 mg/L. The results showed that the final biomass and survival in each treatment were significantly higher in biofloc-reared shrimps when compared to clear water culture (p < 0.05). Among the salinity and BFT treatments, shrimps reared in 15‰ with BFT condition showed better growth and survival than other treatments and achieved a significantly higher final body weight (1.67 g ± 0.067 g). Net shrimp production in terms of growth and survival was 50% higher in the BFT tanks (average body weight = 0.85 ± 0.082 g to 1.67 ± 067 g) than in the control tanks (ABW = 0.61 ± 0.07 g to 0.98 ± 0.07 g). The final survival observed in different biofloc system with varying salinity was significantly higher than respective clear water (CW) system. Total serum protein showed significantly higher levels (120.32 ± 3.68 mg/ml) in 15‰ with BFT treatments than the other. The 15‰ with BFT (0.14 ± 0.011OD/min) and 5‰ with BFT showed more pro-phenol oxidase levels (0.11 ± 0.009 OD/min) of activity than other treatments. Total haemocyte count (THC) was calculated and the highest value of 6.33 ± 0.33 × 106 showed in 15‰ BFT. In conclusion, the lower salinity rearing with biofloc did not show significantly lower growth than optimum range of salinity in case of Penaeus indicus post larvae. [ABSTRACT FROM AUTHOR]

Shrimp grow-out and hatchery systems are being affected by bacterial disease particularly Vibrios. The use of chemotherapeutic agents in aquaculture practices has to lead to the development of resistance among aquatic bacteria. Thus, health management becomes of major importance in aquaculture. Under this situation, progressing bio-inhibitors from marine resources are most appropriate to be considered against pathogenic bacteria. Molecular docking is an appropriate tool in structural biology and computer-assisted drug design to predict and neutralize a target protein of known diseases. In this study, marine macro-alga Ulva fasciata was aimed at developing inhibitors against luminescence disease-causing pathogenic bacteria Vibrio harveyi. U. fasciata was collected from Thoothukudi, Tamil Nadu, India. Extract of U. fasciata was tested against growth and virulence factors of V. harveyi during Penaeus monodon larviculture. Further U. fasciata extract was subjected to GC–MS analysis to identify the biomolecules. The homology modeling of virulent protein, hemolysin of V. harveyi was designed in this study. Hence, it was aimed for molecular docking against the biomolecules identified from U. fasciata extract. During shrimp larviculture, the extract of U. fasciata (200 μg mL−1) exhibited reduction on Cumulative Percentage of Mortality (32.40%) in postlarvae against challenge of V. harveyi infection. Biomolecule Methyl dehydroabietate had showed highest binding affinity among the compounds was evaluated in molecular docking study. Statistical analysis had revealed significant differences (p < 0.05) in trials. Therefore, it was proved that the bio-inhibitors from U. fasciata will be a better option for controlling luminescence disease-causing V. harveyi in shrimp grow-out practices. [ABSTRACT FROM AUTHOR]

A 120-day experiment was conducted to understand the growth and immunomodulatory response of Penaeus vannamei reared in biofloc-integrated periphyton system–like natural substrates like bamboo (NS1), sugarcane bagasse (NS2), artificial substrates like polyvinyl chloride mat (AS1), agricultural shed net (AS2), and a control group without biofloc and substrate. Experiments were carried out in 500-L fiber-reinforced plastic (FRP) tanks at a stocking density of 100 nos/m3 (0.256 g). Shrimps reared in natural substrate-based treatments, (NS1 and NS2) recorded highest average body weight (ABW) and survival followed by artificial ones (AS1 and AS2), and were significantly higher (P < 0.01) compared with control. Significantly higher chlorophylla, ash-free dry matter (AFDM), and THB load were recorded in NS (1 and 2) followed by AS (1 and 2). Contrastingly, the Vibrio load was higher in control than treatments. Relative percentage survival was higher (P < 0.01) in treatments when challenged against V. parahaemolyticus. Serum protein level, phenoloxidase activity, and superoxide dismutase assay were significantly higher in natural and artificial substrate groups when compared to control. Immunomodulatory effects through immune gene study revealed a two fold to four fold upregulation in cytMn-SOD and mtMn-SOD genes in NS groups. Similarly, the lysozyme and prophenoloxidase genes were significantly upregulated in the treatment groups. The results conclude that biofloc with natural followed by artificial periphytic substrates were observed to deliver better performances, protective response, and immunomodulatory effects in pacific white shrimp P. vannamei culture. [ABSTRACT FROM AUTHOR]

Experiments were conducted to explore the colonization of beneficial bacteria in shrimp Penaeus vannamei grown in different sources of biofloc and clear water. Beneficial effect in terms of extracellular enzyme production and antibiofilm activity of the isolated strains was determined. Heterotrophic bacterial population were isolated by using different agar plates and resulted in isolation of 94 isolates in total. Extracellular enzyme production such as amylase, protease, lipase, cellulase, xylanase, and pectinase were screened. Antibiofilm activity of culture supernatants of enzymatic strains against pathogenic Vibrio was also determined. Out of 94 strains screened, 36 strains were found to produce amylase enzyme, 20 strains protease, 27 strains lipase, 6 strains cellulase, and 8 strains xylanase. Totally, 21 isolates selected for further identification and different species of Cobetia, Exiguobacterium, Bacillus, Marinilactibacillus, Staphyllococcus, and Novosphingobium genera from biofloc treatments were identified. In control group animals, strains of Bacillus and Exiguobacterium were isolated and identified. The genus Exiguobacterium was found common in all the different treatments and control. The result showed that shrimp grown on biofloc system allows colonizing more beneficial bacteria in gut than control. Few promising strains under Bacillus genus were found to produce all the extracellular enzymes along with antibiofilm activity. [ABSTRACT FROM AUTHOR]