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The experimental approach was designed for analyzing the nutritional evaluation of formulated feed by replacing conventional fish meal used in fish diet with Padina gymnospora supplementation under laboratory feeding conditions for 45 days on growth indices in brackishwater euryhaline fish, Etroplus suratensis. Proximate composition of control and experimental algal formulated feed was assessed. An increase was observed in the body weight and growth indices of the experimental fishes fed with supplemented algal diets. The analysis determined better growth performance index in those fishes fed on a the formulated diet. [ABSTRACT FROM AUTHOR]

The present study focuses on the green synthesis of iron nanoparticles using plant extracts as reducing, capping, and stabilizing agents. Aqueous seaweed extracts with the addition of iron solution were mixed using a magnetic stirrer which resulted in a color change indicating the formation of iron nanoparticles. The iron nanoparticles were successfully synthesized using Sargassum wightii extract. The synthesized iron nanoparticles were characterized by UV–Vis spectrophotometer, Fourier transform infrared spectroscopy (FTIR), and zeta potential techniques. The UV–Vis spectra showed a peak at 412 to 415 nm. Zeta potential revealed that the synthesized iron nanoparticles were negative and positive charges. FTIR spectroscopy analysis showed the presence of chemical bond and amide group likely to be responsible for the green synthesis of iron nanoparticles. The effect of nano-iron as a dietary iron source on the growth and serum biochemical profile of Etroplussuratensis fingerlings was evaluated. Iron nanoparticles were fed to E. suratensis fingerlings for 60 days with two levels 10 mg (T1) and 20 mg (T2) and a control group without iron nanoparticles. The highest WG% and SGR and lowest FCR were observed in the T2 group which is significantly different (p < 0.05) from other groups. The serum biochemical profile showed significantly increased activity on 20 mg/kg of nano-iron-supplemented diet. The findings of the present study concluded that supplementation of nano-iron at the 20 mg/kg level to the regular fish diet has a better impact not only on growth but also on the overall health of the fish. [ABSTRACT FROM AUTHOR]

The objective of the present study was to analyze the morphometric and meristic variations of an estuarine fish, Etroplus suratensis, in five locations along the South Indian coastal region. In total, 651 individuals were collected and 16 morphometric and six meristic counts were taken. The results of univariate (ANOVA) and multivariate (Principal Component Analysis, PCA) analyses showed that the east coast stocks (Machilipatnam, Mudasalodai, Rajakkamangalam) have overlapping morphological characteristics, whereas the west coast stock (Cochin) was distinctly different, but there were no significant differences observed in meristic characters among the five stocks. Therefore, it was presumed that Machilipatnam, Mudasalodai, and Rajakkamangalam were the same stock. The morphometric data discriminated E. suratensis into two stocks, i.e., those of the east and west coasts. However, further molecular-based analysis is very much needed to validate these stocks.

Three seed production techniques of pearlspot Etroplus suratensis (Bloch)—pond rearing, tank rearing, and pit rearing—were evaluated in farmers' fields to assess production success, practicality, and economic viability. The pond rearing technique stocked mature pearlspot in ponds with artificial substrates and reared seed in the pond itself. The tank rearing technique collected pearlspot eggs from the pond and hatched and reared them in separate tanks. The pit rearing technique trapped pearlspot fry using a specially designed falling trap and reared them in ponds with an artificial feed. The average fingerlings productions per spawning per pair were 47 ± 27, 93 ± 22, and 578 ± 82 respectively. The pit rearing technique was reported to be preferred by farmers because of its ease and cost effectiveness. The homing instinct of pearlspot brooders with spawn to the nursing pits was observed even weeks after hatching. [ABSTRACT FROM AUTHOR]

Investigation of four edible fishes (Etroplus suratensis, Oreochromis mossambicus, Lates calcarifer, Chanos chanos) collected from a fish landing center along Cochin Backwaters has done for caligid infestation. Of these, caligids were detected only from Etroplus suratensis and was identified to be Caligus rotundigenitalis. Parasites were attached to the inner side of operculum of host which indicates strong site preference. The annual observation of prevalence, mean intensity and abundance were found to be 19.21%, 1.051 and 0.202 respectively. Variation of prevalence with respect to the different length groups of E. suratensis has discussed in this paper. Damages of the inner side of operculum and increase in mucous production were noticed as a result of copepod attachment. [ABSTRACT FROM AUTHOR]

Objectives: Microplastics are emerging contaminants in aquatic environments, and there is a global concern about the impact of this pollutant on the ecosystem. In the present study, the toxicological impacts of polyvinyl chloride microplastics (PVC MPs) on the fish Etroplus suratensis, the state fish of Kerala, were carried out. Methods: Acute and chronic toxicity tests of PVC MPs were conducted for juvenile fishes. The 10-day half-maximal effective concentration (EC50) was found after the acute toxicity test. Quantification of MPs in the intestine and faecal matter, parameters of oxidative stress [superoxide dismutase (SOD), malate dehydrogenase (MDH), and catalase (CAT)], brain and gill acetylcholine esterase (AChE) activity, behavioural changes, and blood biomarkers (red blood cell (RBC) and white blood cell (WBC) count) were analysed after chronic toxicity test. Results: The 10-day half-maximal effective concentration (EC50) value of PVC MPs on E. suratensis was 34.89 mg L−1 with a 95% confidence interval of 31.43 to 38.59. The antioxidant enzymes superoxide dismutase (SOD), malate dehydrogenase (MDH), and catalase (CAT) showed significant changes upon MP exposure. The brain and gill acetylcholine esterase (AChE) activity showed a dose-dependent decrease (p < 0.001). The frequency of behavioural changes such as fin flickering, burst swimming, and jerking movement increased with increased exposure concentration. The haematological indices like red blood cell (RBC) and white blood cell (WBC) count showed a significant decrease (P < 0.001) at the highest exposure concentration when compared to the control. Conclusion: The study thus provides an insight into the effects of microplastic exposure on fishes. Significant changes in growth, antioxidant enzyme activity, acetylcholine esterase activity, behaviour, and haematological biomarkers were observed. [ABSTRACT FROM AUTHOR]

The present study was carried out to observe the mitotic chromosomes in Etroplus suratensis from two different locations viz., Bhatkarwada and Karla along the Ratnagiri coast, Maharashtra, India. To obtain metaphase chromosomes, the fishes were treated with (0.005%) colchicine solution and the gill tissue was used to obtain the metaphase chromosomes. The homologous chromosomes were mapped and measured using software IdeoKar 1.3 provided by the University of Kurdistan, Iraq. The current study showed that the specimens collected from both the locations had the same diploid chromosome number i.e., 2n= 48 sub telocentric/acrocentric chromosomes, with a few differences in other karyomorphological characters. The fundamental arm number in both the cases was 96. The result indicated that the specimens of E. suratensis collected from the two locations along the Ratnagiri coast belonged to the same stock. No sex chromosomes in both the sexes had been found to be dissimilar either in size or shape for E. suratensis from both the stations. [ABSTRACT FROM AUTHOR]

A seed rearing experiment was attempted to evaluate the effects of stocking densities in the biofilm‐based system reared with pearlspot, Etroplus suratensis on different aquaculture parameters. Pearlspot advanced fry of size (4.67 ± 0.04 cm/1.71 ± 0.03 g) stocked at four different stocking densities viz 50 fish (T1); 100 fish (T2); 150 fish (T3) and 200 fish (T4) m−3 in the biofilm‐based rearing system and at the rate of 150 fish m−3 in the clear water fed (CWF) system tanks. The total ammonia nitrogen and dissolved oxygen levels in biofilm tanks with different stocking density were significantly lower than CWF. Diatom was found as dominant plankton in all biofilm treatment tanks in water as well as on substrate. The growth parameters were found to significantly decrease with increasing stocking density in the biofilm‐based rearing system. The significant highest individual growth parameters and significantly lowest fish biomass were found in T1. Final fish biomass was found to increase with increasing stocking density up to 150 advanced fry m−3 and then reduced due to decreased survival. Body composition analysis of E. suratensis showed increased protein and decreased lipid levels in all biofilm‐based rearing system treatments at different stocking densities compared with clear water fed system. The present investigation findings on plankton abundance, growth, body composition and blood parameters at different stocking densities will provide guidelines for selecting appropriate stocking density for pearlspot advanced fry to fingerling rearing in a low saline biofilm‐based system without providing a supplementary diet. [ABSTRACT FROM AUTHOR]

The accumulation trends of Cu, Zn, Pb and Ni and their effects on two native species, Etroplus suratensis and Villorita cyprinoides from Cochin estuary and their biomarker responses were explored. Bioaccumulation and metal selectivity index (MSI) in E. suratensis for gill and liver showed the highest accumulation for Zn (209.33 ± 17.14 mg kg−1) followed by Cu (64.16 ± 8.07 mg kg−1), while in V. cyprinoides Cu showed the highest accumulation (80.78 ± 6.92 mg kg−1) in gill tissue followed by Zn (65.28 ± 7.06 mg kg−1). Histological alterations were evaluated in gill and liver tissues of E. suratensis using histopathological index (Ih) method. Lamellar hyperplasia and deformed lamellar architecture were the evident changes in gill tissue, while the alterations in liver tissues were marked by the presence of melanomacrophage centers and necrotic lesions in liver parenchyma. The high target hazard quotient (THQ) obtained for Pb (0.94) indicated that the daily consumption of aquatic products contaminated with metals Pb, Cu and Zn has obvious health risk to human consumption. Thus, the elevated metal accumulation rate in the tissues with supportive histological changes suggests that these alterations can serve as definite signature of heavy metal contamination in native organisms of Cochin estuary. Research highlights: The tissue-specific bioaccumulation and metal selectivity index (MSI) of E. suratensis and V. cyprinoides revealed significantly higher accumulation of Cu and Zn compared to Pb and Ni throughout the study with higher rates during non-monsoonal periods. The histopathological studies in fish, E. suratensis from field conditions portrayed significant histopathological alterations such as hyperplasia, deformed secondary lamellae in gill tissues; melanomacrophage centres and necrotic lesions in liver. The estimation of human health risk assessment of heavy metals (Cu, Zn and Pb) of E. suratensis from Cochin estuary denoted a possible risk from consumption of fishes from the Cochin estuary. [ABSTRACT FROM AUTHOR]

The Static bioassay test was conducted to estimate acute toxicity tests (96-hr LC50 and lethal concentration) of Titanium dioxide nanoparticles (TiO2 NPs) was conducted with a fingerlings of species Etroplus suratensis for 96 h. Toxicity test is most reliable for accessing effect of toxicants on aquatic life. Different concentrations of TiO2 NPs were exposed to fishes. Fish were exposed to different chosen concentration of TiO2 NPs, and after 96 hours and six hours between observations of mortality, the statistics on mortality were determined. The results showed that acute toxicity of nanoparticles to fish after 96 hours of exposure could reveal that exposure to nanoparticles may have harmful effects on fish that ultimately damage the health of aquatic ecosystems. [ABSTRACT FROM AUTHOR]

Lectins are hemagglutinating glycoproteins which act as pathogen recognition receptors that can bind to the pathogen-associated molecular patterns. Shrimp lectin (Md-Lec) is a lectin that is reported to have antimicrobial property. In this study, the CuS nanoparticles (CuS NPs) which were previously reported to have wide range of antimicrobial activity were conjugated with Md-Lec. Thus, their minimum inhibitory concentration (MIC) against aquatic pathogens was reduced four times than that of their individual activity. Moreover, antibacterial and antibiofilm assay was performed with Md-Lec, pCuS NPs, and Md-Lec conjugated with pCuS NPs (Md-Lec-pCuS NPs) against Aeromonas hydrophila at 25, 50, and 100 μg/mL. The hydrophobicity index and EPS (extracellular polysaccharide) production of A. hydrophila were decreased after treating with Md-Lec-pCuS NPs. The non-specific immune parameters—lysozyme assay, peroxidase assay, and respiratory burst activity—were elevated considerably in the infected fishes that are treated with Md-Lec-pCuS NPs at their MIC. Further, immune gene (COX2, MyD88, and LEC) expression analysis at different time intervals was also done in the infected Etroplus suratensis that are treated with Md-Lec-pCuS NPs at 3.13 μM concentration. The results reveal that the immune gene expression was upregulated at the 6th hour of infection in the infected fish that are treated with Md-Lec-pCuS NPs (3.13 μM) and thus it can be used as a therapeutic agent which can act as an immunostimulant for the production of disease-free fishes in aquaculture industry. [ABSTRACT FROM AUTHOR]

Etroplus suratensis (Bloch, 1790) is a highly exploited endemic cichlid fish species inhabiting the Cochin Estuary situated on the South-west coast of India. The study was conducted with the sample of 599 specimens with TL ranged 67–249 mm and TBW ranged 7–280 g. Females were predominant in the catches and the overall sex ratio was 1.00 : 1.18, which significantly deviated from theoretical 1 : 1 distribution with 45.9% males and 54.09% females. The pattern of gonadosomatic index and proportion of mature individuals suggest two peaks in the spawning season of E. suratensis occurred between May to August and November to January. The length at 50% maturity for males and females was estimated at 167 and 169 mm TL respectively. The absolute fecundity estimates vary between 2147 and 4432 eggs with an average of 3112 and the relative fecundity fluctuated between 18 and 23 eggs g–1 with an average of 21. The results of the present study provide option to develop sustainable fishery management practices such as closed season, mesh size regulations and development of fishing sanctuaries to conserve this commercially important cichlid species. [ABSTRACT FROM AUTHOR]

Multi-biomarker approach is recognised as a complementary tool for environmental monitoring studies to better appraise how pollutants affect ecosystems. This study examined histological alterations in the liver tissues and nuclear abnormalities in the peripheral erythrocytes of two native fish species inhabiting the Kelani River (Etroplus suratensis and Dawkinsia singhala) as 'effect biomarkers' for assessing pollution impacts. Surface water and native fish were sampled from two polluted sites in the lower reach (Kaduwela and Mattakkuliya) and a less polluted site in the upper reach (Ruwanwella) of the river covering rainy and dry periods. Physico-chemical analyses of surface water confirmed an increasing trend of pollution towards the lower reach of the river. Significantly greater liver histopathologic condition indices and erythrocytic nuclear abnormality frequencies (p < 0.05) were found in the fish inhabiting lower reaches of the river compared to those in the upper catchment at Ruwanwella. Biomarker responses revealed that the fish populations inhabiting the polluted sites in the river are under stress especially due to hepatic damage and genotoxicity. The results suggest that endemic and nationally threatened fish species in the riverine ecosystem may be at risk due to the contaminant stress under long term exposure. This study supports utility of erythrocyte nuclear abnormality and liver histopathological biomarker responses of native fish as cost effective tools for the identification of potential biological hazards of river pollution. [ABSTRACT FROM AUTHOR]

Aquaculture of Etroplus suratensis is being practised at various water salinities. In this investigation, morphological responses of gill tissue of E. suratensis to various osmotic changes induced by freshwater (0%) and sea water (36%) were studied. Ultra-structural studies revealed significant decrease in the density of type I Mitochondrial rich cells in the apical surface of gills at 18% and complete disappearance of these cells at 36%. Type III subtype density increased consistently from 0% to 36%. Variations in type II cells density were comparatively less in any of the experimental groups. Light microscopic changes included reduction in mucous cell number with increasing salinity. Haemorrhages, lamellar fusion, lamellar curling, lifting of epithelium & hyperplasia are major histological responses to salinity shock. Observable clinical signs in fish exposed to increased salinity changes included agitated behaviour and respiratory distress. [ABSTRACT FROM AUTHOR]

Abstract The present study reveals purification and characterization of a C-type lectin from the serum of pearl spot, Etroplus suratensis (Es-Lec). The Es-Lec was purified by affinity chromatography with mannose coupled sepharose CL-4B column and it exhibits single band with a molecular weight of 75 kDa in SDS-PAGE. The surface morphology of purified Es-Lec displays the homogeneous nature of protein. A distinct peak with a retention time of 2.958 min was appeared in high performance liquid chromatography (HPLC), X-ray diffraction (XRD) analysis expresses a single peak at 31.8372̊ and MALDI-TOF peaks which shows the purity and crystalline nature of the protein respectively. Functional analysis of purified Es-Lec exhibits yeast agglutination activity against Saccharomyces cerevisiae and has the ability to agglutinate the human erythrocytes, which was observed by light microscopy and haemagglutination inhibition was also done. In addition, purified Es-Lec showed the broad spectrum of antibacterial activity against Gram negative Vibrio parahaemolyticus and Aeromonas hydrophila. Antibiofilm potential of purified Es-Lec against selected Gram-negative bacteria exhibited the disruption of biofilm architecture at the concentration of 50 μg ml−1 and also it exhibited antiviral and anticancer activity. Graphical abstract Image 1 Highlights • Es-Lec of 75 kDa was purified by mannose-sepharose column chromatography. • Its crystalline nature, quality and purity were assessed by XRD, HPLC and MALDI-TOF respectively. • Es-Lec exhibited haemagglutination and yeast agglutination activity. • They possess antibacterial, antibiofilm and antiviral activity. • They exhibited an anti-cancer potential against breast cancer cell lines MDA-MB-231. [ABSTRACT FROM AUTHOR]

Viral nervous necrosis (VNN) affects more than 120 species mostly belonging to the order Perciformes. However, none of the brackishwater species belonging to the family Cichlidae under the order Perciformes are reported to be susceptible. Hence, the present experiment was undertaken to study the susceptibility of the brackishwater cichlid, pearlspot, Etroplus suratensis to NNV. Thirty‐day‐old pearlspot larvae were infected with NNV by immersion. Mortality was recorded till 14 days post‐infection, and the infected larvae were subjected to nested RT‐PCR and histology. The virus was isolated from infected larvae using SSN‐1 cells. To study the replication of the virus in vitro, primary cultured brain cells of E. suratensis and IEK cells were infected with NNV. No mortality was observed in any of the control or experimentally infected larvae. However, the experimentally infected larvae were positive for NNV by nested RT‐PCR and the virus was isolated using SSN‐1 cells. Further, the infected pearlspot brain cells and IEK cells showed cytopathic effect at second and third passage of the virus and they were positive for NNV by nested RT‐PCR. Pearlspot is relatively resistant to VNN although the virus could replicate in the larvae and in cell culture. [ABSTRACT FROM AUTHOR]

Abstract Copper (Cu) and zinc (Zn) play a vital role in the growth and development, however increased uptake causes deleterious effects in normal functioning of organisms. We have demonstrated in this contribution the tolerance limit of Cu and Zn on Etroplus suratensis (pearl spot) by Continuous Flow Through (CFT) bioassay and the biomarker responses. The accumulation for Cu, Zn and selected trace metals (Cr, Cd, Ni and Pb) from field conditions, as well Geo-accumulation index (I geo) and Contamination factor (C.F) suggested moderate to heavy pollution in the Cochin estuarine system. The 96 h LC 50 values for Cu was 1.74 ± 0.04 mg L−1and that for Zn was 24.36 ± 0.58 mg L−1 at 95% confidence interval. No observed effect concentration (NOEC) and low observed effect concentration (LOEC) for Cu and Zn were derived based on the survival rates. Chronic toxicity values for Cu and Zn were 0.23 mg L−1 and 2.005 mg L−1 respectively for 30 days period. The histological, biochemical, hematological and behavioral parameters showed significant variations at sublethal concentrations. Lamellar hyperplasia in gills, vacuolation combined with necrosis in liver, increased occurrence of melanomacrophage centres in spleen were noticed at chronic levels for both Cu and Zn. Tissue specific bioconcentration was observed for zinc and copper in gill and liver respectively, with least rate of bioconcentration observed in muscle tissues. Malaonate Dehydrogenase (MDH), Super oxide dismutase (SOD), Nonspecific esterase (EST) activity significantly varied compared to control at NOEC and LOEC values in both the metals. The hematological and genotoxic alterations as decrease in erythrocyte count, lymphocytes, hemoglobin concentration and hematocrit percentage were significantly reduced (p < 0.05) and increased thrombocytes and neutrophils, increased frequency of micronuclei, lobed, blebbed and notched nuclei and binucleate cells were characteristic for the metals at the sublethal concentrations. The frequency of behavioral changes remained significantly higher at chronic level than the control group. Thus such CFT based studies are important for precisely mapping the toxicity changes in organisms and also to develop suitable water quality guidelines. Highlights • Chronic toxicity values for Cu and Zn on Etroplus suratensis were 0.23 mg L−1 and 2.005 mg L−1 respectively. • Analysis of water and sediment samples from Cochin estuary showed contamination from Cu and Zn. • Tissue-specific pattern of bioaccumulation of Cu and Zn were observed during study. • Evident biomarker changes in Etroplus suratensis were observed on exposure to Cu and Zn. [ABSTRACT FROM AUTHOR]

The present study reports the complete sequences of Aquaporin 1 (AQP1) gene and partial sequences of genes, Sodium/potassium-transporting ATPase subunit alpha-1 (Na/K-ATPase α1 subunit), Osmotic Stress Transcription Factor 1 (OSTF1), Transcription Factor II B (TFIIB), Heat Shock Cognate 71 (HSC71) and Heat Shock Protein 90 (HSP90) obtained from mRNA and genomic DNA of Etroplus suratensis. They are candidate genes involved in stress responses of fishes. AQP1 gene was 2163 bp long. Its mRNA sequence has 55 bp 5′ UTR, 783 bp open reading frame (ORF), 119 bp 3′ UTR, three intronic regions and 90% identity with AQP1 of Oreochromis niloticus. The partial Na/K-ATPase α1subunit gene obtained 5998 bp length with an ORF of 2213 bp and 12 intronic regions. The partial OSTF1, TF IIB, HSC71 and HSP90 mRNA sequences obtained were 1473 bp, 587 bp, 1708 bp and 151 bp in length respectively. All the genes showed a high sequence similarity with respective genes reported from fishes. Comparison of AQP1 and Na/K-ATPase α1 genomic DNA sequence of E. suratensis collected from different water system showed two type of AQP1 with one synonymous mutation in exon-1 and higher sequence difference in intronic regions (including addition, deletion, transition and transversion mutations) with few synonymous and non-synonymous mutations in the exons of Na/K-ATPase α1. The sequence information of these major candidate genes involved in stress responses will help in further studies on population genetics, adaptive variations and genetic improvement programs of this cichlid species having aquaculture, ornamental and evolutionary importance. [ABSTRACT FROM AUTHOR]

Effect of Bis-2ethylhexyl phthalate (DEHP) on commercially important tropical fish pearl spot has not been demonstrated at environmental concentrations along with depuration. The species is estuarine, juvenile and difficult to maintain but widely consumed and well distributed in tropical estuaries. Antioxidant activity of SOD, CAT and GPx was enhanced on all exposure days for gill and muscle suggesting high oxidative stress, except on day 5. Detoxifying enzyme-GST behaved differentially in gill and muscle tissue after depuration, depicting inhibited activity of GST in gill leading to lipid peroxidation. However, the muscle tissue was able to recover from stress after 7 days of depuration with the help of detoxifying enzymes. Overcompensation of antioxidant activity was observed over disruption of homeostasis defining hormesis effect. Integrated biomarker (IBR) index depicted high toxicity during entire exposure time, but after depuration, gill could not mediate LPO at lowest concentration (10 μg/l) while muscle tissue recovered, suggesting persistence of stress in gill. [Display omitted] • DEHP at environmental concentration inducts oxidative stress in E. suratensis • Gill fails to eliminate ROS generated even after depuration period of 7 days. • Muscle of E. suratensis can cope with the DEHP generated stress with 7 days of depuration. • IBR delineates toxicity damge in gill induced by DEHP. [ABSTRACT FROM AUTHOR]

Fishes are always exposed to various environmental stresses and the chances of succumbing to such stresses are of great physiological concern. Any change in temperature from the ambient condition can induce various metabolic and physiological changes in the body. The present study evaluates the effects of temperature induced stress on the antioxidant profile of Etroplus suratensis such as superoxide dismutase, catalase, glutathione peroxidase and lipid peroxidation. Fishes of same size were kept in a thermostatized bath at three different temperature regimes viz 16 °C, 27 °C (ambient temperature) and 38 °C for 72 h. These temperatures were selected based on the CT Max (Critical Thermal Maximum) and CT Min (Critical Thermal Minimum) exhibited by E. suratensis . Superoxide dismutase and catalase activity was found maximum in brain and muscle respectively during the 48th hour of exposure in fishes kept at 38 °C. At 16 °C the antioxidant response of glutathione peroxidase was maximum in muscles, whereas the lipid peroxidation rate was found to be high in gills compared to other tissues. The profound increase in the levels of oxidative stress related biomarkers indicate that the thermal stressors severely affected oxidative state of E. suratensis by the second day of experiment. Such down-regulation of redox state accompanied with the induction of oxidative stress cascade may lead to physiological damage in various tissues in fishes, in vivo. However current data indicate that a transition to low and high temperature environment from ambient condition severely affected the levels and profile of the antioxidant markers overtime in E. suratensis . [ABSTRACT FROM AUTHOR]

Increasing the breeding frequency and reproductive performance of pearlspot, Etroplus suratensis in small tank system by manipulating parental care and salinity is reported. A total of 3 experiments were carried out to evaluate the reproductive performance of pearlspot. In the first experiment on breeding of pearlspot involving parental care (without larval separation), production of a single batch of offspring per pair of parent fish (294 larvae, 24–43 fry) was observed after 90 days. Whereas the second experiment on pearlspot breeding by curtailing parental care (with larval separation) demonstrated a higher breeding frequency; 6 in 120 days. The average inter-spawning interval and larval production were 17.6 ± 1.12 days and 1333.3 ± 143.0 respectively. The third experiment was to evaluate the breeding frequency of pearlspot at low (5.40 ± 0.75‰) and high salinity (27.20 ± 0.80‰) by curtailing parental care. The average inter-spawning interval was found to be significantly ( p < 0.05) lower (32.14 ± 4.38 days) at low salinity when compared to high salinity (64.37 ± 12.95 days). Similarly, the breeding frequency was also higher at lower salinity in 215 days (5.66 ± 0.66 at low compared to 3.67 ± 0.67 at high salinity). The present study demonstrated that i) curtailing parental care through larval separation can be used to improve the breeding frequency and reproductive performance of pearlspot in captivity ii) relatively lower salinity reduced the inter-spawning interval of pearlspot iii) feasibility of breeding pearlspot in small tank system (1000 L). [ABSTRACT FROM AUTHOR]

An experiment was conducted to compare the efficiency of biofilm production in natural and artificial substrates and to study their effect on water quality and growth of Etroplus suratensis. Four different substrates were used for biofilm formation: paddy straw (T1), sugarcane bagasse (T2), polyvinylchloride (PVC) pipe (T3) and plastic sheet (T4). The experiment was carried out in mud-bottomed fibre-reinforced plastic tanks (300 L) in triplicates. About 3000 cm surface area (600 g) of each substrate was suspended in water supplemented with fertilizers. Only cow dung and urea were applied in control tanks. The tanks were stocked with 25 fishes with average weight of 9.1 ± 0.22 g. The overall mean value of heterotrophic bacteria in substrate was found higher in straw followed by bagasse, plastic and PVC. The dominant genera of bacteria in the substrate were Bacillus, Pseudomonas and Micrococcus in that order of preponderance. The mean phytoplankton and zooplankton density on the substrates were higher in bagasse followed by straw, plastic and PVC. The biofilm developed on the substrate significantly reduced the ammonia nitrogen and nitrite-nitrogen content of water. The growth of fishes was significantly ( P < 0.05) higher in substrate-based treatments than that in the control with better results in bagasse followed by straw, plastic and PVC. The conclusions of the present study are that biofilm produced on natural substrates, especially on bagasse, enhanced growth of E. suratensis and reduced the necessity of water exchange during the culture, which certainly decreases the cost of Etroplus production. [ABSTRACT FROM AUTHOR]

Innate immune system recognises pathogen-associated molecular patterns (PAMPs) by limited number of germline encoded and non-clonally developed pathogen recognition receptors (PRRs). Retinoic acid-inducible gene I (RIG-I)-like receptors (RLRs) are important cytosolic PRRs for sensing viral RNAs. The receptor encoded by melanoma differentiation associated gene 5 (MDA5), an RLR, recognises viral RNA and enhances antiviral response in host cells. The full-length MDA5 cDNA in Etroplus suratensis was cloned and found to have 3673 nucleotides encoding a polypeptide of 978 amino acids. The deduced amino acid sequence contains four main structural domains: two CARD domains in the N-terminal region, a DExDc (DEAH/DEAD box helicase domain), HELICc (C-terminal helicase) domain and a C-terminal regulatory domain (RD). Phylogenetic analysis revealed a close relationship of E. suratensis MDA5 ( Es MDA5) with MDA5 of Neolamprologus brichardi and Oreochromis niloticus , both belonging to Cichlidae family. Es MDA5 transcripts were ubiquitously expressed in all the 12 tissues tested in healthy fish. Although, transcript level was found to be the highest in muscle, high expression was also detected in the spleen, head kidney and hindgut. In poly I:C-injected fish, Es MDA5 transcripts showed peak expression in the spleen, intestine and heart at 12 h post-injection (hpi). However, in gill and kidney tissues, maximum up-regulation of Es MDA5 was observed at 6 and 48 hpi, respectively. Further, liver tissue showed an increasing trend in expression profile from 6 to 48 hpi. Interferon promoter stimulator-1 (IPS-1) gene, an adaptor triggering RIG-I- and MDA5-mediated type I interferon induction, also showed up-regulated expression at initial time-points in poly I:C-injected E. suratensis . The constitutive expression and up-regulation of Es MDA5 and the IPS-1 genes in different tissues indicate that Es MDA5 may play an important role in sensing viral PAMPs in conjunction with IPS-1. [ABSTRACT FROM AUTHOR]