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Recently reports of orange chromide (Etroplus maculatus) stocked in the tanks showed mass mortality in Mangaluru, India. E. maculatus is an ornamental fish, which is exported to different countries around the globe and these belong to the genus of Etroplus where another two species share the same genus [E. canarensis (Canara pearlspot) and E. suratensis (Pearlspot)]. These native fish were discovered in the Western Ghats which is one of the highest biodiversity spots in the world. The goal of the current investigation was to pinpoint the aetiological agent linked to mass mortality of E. maculatus. The E. maculatus had internal symptoms of an enlarged spleen and kidney, while symptoms externally included discoloration of the body and petechial hemorrhages. Infectious spleen and kidney necrosis virus (ISKNV) of the genus Megalocytivirus was identified as the aetiological agent by polymerase chain reaction (PCR) amplification of the major capsid protein (MCP) gene with an amplicon size of 563 basepair (bp). The isolated ISKNV sequence was found to be closely related to the ISKNV isolated from Malaysian Molly fish (Xiphophorus hellerii) and Australian Angel fish (Pterophyllum scalare) according to phylogenetic analysis. The sequence was subsequently added to the NCBI GenBank database with the accession number ON149089.1. Girisha et al (2020) earlier reported that the SISS cell line was utilized for the purpose of virus propagation and same was followed in the present study. Cytopathic effects (CPEs) were evident in the infected SISS cells showing the rounding, expansion and eventually cell detachment from the flasks after 10 days. The current study confirms that E. maculatus, an endemic species is susceptible to ISKNV infection, suggesting that its host range has expanded especially in India after our report from 2020. [ABSTRACT FROM AUTHOR]

Viral nervous necrosis (VNN), or viral encephalopathy and retinopathy caused by nervous necrosis virus (NNV), is an acute viral disease of fish, resulting in high mortality globally in cultured marine fish. The pathogen, Betanodavirus belonging to the family Nodaviridae, has been widely documented in both farmed and wild fish, besides in invertebrate species across the habitat barriers. However, cichlid fish, in particular Etroplus species, have a low susceptibility or resistance to this disease. The present study was undertaken to check the susceptibility of a brackishwater cichlid, orange chromide (Etroplus maculatus) through intramuscular injection and immersion challenge by NNV (RGNNV genotype). Intramuscular injection (10 μl) with NNV (105 viral particles ml−1) resulted in cumulative mortality of 50% at 15 days of post-infection (dpi), while immersion challenge in NNV spiked sea water (105 TCID50 ml−1) resulting in a mortality of 25% at 19 dpi. Unlike many marine fish which showed 100% mortality within 3–5 days, E. maculatus challenged through both the routes exhibited severe clinical symptoms for 2–3 weeks followed by a recovery stage and moderate level of mortality. Reverse transcription polymerase chain reaction (RT-PCR) tests on live fish sampled during the course of the experiment and the dead fish exhibiting symptoms in both challenge groups tested NNV-positive. Histological examination of fish in challenged groups showed VNN-specific lesions characterized by vacuolations in the brain and eye with more severe lesions in the injected group than the immersion group. In survived fish, no clinical sign was observed, but NNV could be detected by RT-PCR with moderate to severe vacuolations in the brain and eyes until 30 dpi. Despite the virus entering the body and triggering typical symptoms of VNN, the fish appeared to exhibit moderate resistance with a survival of 50–75%. The results indicate that E. maculatus could serve as a brackishwater fish model to study host-pathogen interaction and development of resistance for potential application in NNV-vaccine studies. [ABSTRACT FROM AUTHOR]

Abstract: The effects of sub-lethal concentrations of lindane on behavioral, hematological and histological parameters in Etroplus maculatus were investigated. The LC50 value of lindane for E. maculatus was estimated using the Probit method and was found to be 0.028 mg/L. The red blood cell count (RBC) and the hemoglobin (Hb), hematocrit (Ht), mean corpuscular hemoglobin (MCH), mean corpuscular volume (MCV) and mean corpuscular hemoglobin concentration (MCHC) were significantly reduced (p > 0.0001) in fish exposed to the toxicant concentrations compared to the control groups. However, the white blood cell count (WBC) was observed to be significantly higher (p < 0.0001). Observations of the tissues showed that lindane had profound destructive effects on the gills, liver and kidney of the fish. The gills showed proliferation of the lamellar epithelium and lamellar fusion, the liver showed necrosis and the kidneys had constriction of the tubular lumen. The frequency of observed behaviors had the same levels of significance throughout the period of study. There was a reduction in the frequency of occurrence between test concentrations, but remained significantly higher than the control. The study shows that lindane is harmful to E. maculatus at sub-lethal concentrations and that the application of this pesticide close to bodies of water is a dangerous threat to aquatic life. [Copyright &y& Elsevier]

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]