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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]

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]

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]

This paper characterize microplastics (MPs) in the heavily urbanized, brackish water Vembanad Lake (India), focussing on some commercially important bottom-feeding fishes and shellfish (Arius maculatus, Etroplus suratensis, E. maculatus and Villorita sp.). The average abundance of MPs was higher in the water column (872 ± 573 nos./m3) than in finfishes (15 ± 13 particles per fish) and shellfish (23 ± 20 nos./ind.). Fibre was the most abundant MP type in the water and the organisms examined. The size of MPs obtained from finfishes ranged between 0.04 and 4.73 mm (4 ± 3 mm), with a majority of particles being <4 mm. No correlation was found between biological features (e.g. gut length, mouth size) of fishes and the size of MPs in their gut. In Villorita sp. , the abundance of MPs was positively correlated with the size of the individuals. Raman spectroscopy confirmed the presence of chlorinated polyvinyl chloride, polyethylene, polypropylene and polyester in the samples. [Display omitted] • Microplastics present in all samples of bottom dwelling fishes and shellfish • Higher MP load in water column than in fishes and shellfish • MP types included chlorinated PVC, polyethylene, polypropylene and polyester. • More microplastics consumed by Arius maculatus and Villorita sp. • MP load in Villorita sp. correlated positively with size of individuals. [ABSTRACT FROM AUTHOR]