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In the present study, the DNA barcoding of the nematode parasite infecting Ompok bimaculatus and Nemacheilus anguilla fish species was carried out in Barvi Reservoir, Maharashtra. To ascertain the taxonomic status of these nematode parasites, an 18S gene marker was used. Accurate identification of fish parasites is essential to formulate preventive strategies and to study host–environment relations. The present study did barcoding of the nematode parasites of the fishes caught from the Barvi Reservoir using the nuclear 18S rDNA (SSU) sequence. The nuclear 18S rDNA (SSU) was amplified into two overlapping amplicons and sequenced to identify the species based on the sequence similarity with the NCBI GenBank database. The present study sequences (both fragments) showed 98% similarity with the species of Eustrongylides. The average genetic distance value between the present study sample and species of Eustrongylides was 0.003. In the phylogenetic tree also, the sequence was clustered with the species of Eustrongylides with significant bootstrap values. The present study identified the nematode parasite of the fish caught from the Barvi Reservoir, as species of Eustrongylides. The species‐level identification could not be possible due to the insufficient/lack of reference sequences in the database. It indicates the knowledge gap concerning the species‐specific molecular markers for nematode parasites of the fish. [ABSTRACT FROM AUTHOR]

Hepatopancreatic microsporidiosis (HPM) caused by Enterocytozoon hepatopenaei (EHP) causes substantial economic losses to the shrimp farming industry. Most research on EHP was focused on Penaeus vannamei due to its widespread farming and impact. The information on EHP infection in farmed tiger shrimp, Penaeus monodon, is scarce, especially considering its re-introduction and use of specific pathogen-free (SPF) seeds in India. A polymerase chain reaction–based (two-step PCR) survey targeting the spore wall protein (SWP) gene and SSU rRNA gene was conducted to understand the prevalence of EHP in P. monodon farms across six states, three each on the east and west coasts of India. While only 19 of 63 farms (30.15%) surveyed during the study revealed the presence of EHP using SWP-specific PCR, 38 farms (60.31%) were found to be positive with SSU rRNA PCR. Coast-wise, prevalence estimated using SWP-specific PCR showed 35% in the east and 21.7% in the west. However, only one of the farms showed EHP in the first step of PCR. The low level of infection, as indicated by the PCR analysis, was further validated and confirmed by histology and quantitative real-time PCR (qPCR). The EHP load ranged from 1.0 × 103 to 3.7 × 106 copies/µg DNA, and histology of the hepatopancreas showed only mild pathological changes and inclusion-like bodies similar to the developmental stages of EHP. Some of the samples showed bacteria-induced hemocyte infiltration and nodule formation. However, no microsporidian spores could be noticed in the histological sections. The phylogenetic analysis of sequences of SWP-specific PCR amplicons showed similarity with earlier reported EHP strains from P. vannamei from Thailand, Latin America, and India. A statistical epidemiological study to identify risk factors associated with HPM revealed the presence of EHP infection in previous cultures, the use of wild seeds and continuous farming as potential risk factors, and the use of SPF seeds and bleaching as protective factors. P. monodon is susceptible to EHP infection, yet the impact on the species is significantly lower than that reported in P. vannamei. The present report forms the latest data on the prevalence of EHP in P. monodon farms in India. [ABSTRACT FROM AUTHOR]

Immunoglobulin M (IgM) is the major isotype among teleost immunoglobulins. The present study was aimed to explore IgM heavy chain gene and its expression profile in rohu. Full-length IgM heavy chain cDNA of rohu consisted of 1994 bp encoding a polypeptide of 576 amino acid residues including a leader peptide, variable (VH) and constant (CH1–CH2–CH3–CH4) domains confirming the secretory form of IgM. The sequence carries conserved residues such as cysteine, tryptophan and amino acid motifs like 'YYCAR' and 'FDYWGKGT–VTV–S'. The predicted 3 D model confirmed various domains of rohu IgM heavy chain. Phylogenetic tree analysis revealed that IgM heavy chain gene of rohu shared the same cluster with that of other cyprinid fishes. Tissue distribution analysis showed the predominant level of IgM heavy chain gene expression in kidney, spleen and intestine. IgM heavy chain gene expression in rohu kidney was found to be up-regulated and reached a maximum at 7 days post-challenge with Aeromonas hydrophila. These findings demonstrate the first report of full-length secretory IgM heavy chain gene in rohu. Besides, IgM heavy chain gene was highly expressed in major lymphoid tissues and bacterial challenge influenced its expression which further confirmed its role in the adaptive humoral immune response. [ABSTRACT FROM AUTHOR]

In the present study, the microsporidian infecting wild shrimp were characterized by histological and histochemical studies. A six months survey to examine the microsporidian infection in feral shrimp revealed that only Parapenaeopsis stylifera was infected with a microsporean, Perezia sp. Other species examined (Metapenaeus brevicornis, Metapenaeus affinis and Solenocera sp.) did not reveal any infection. The prevalence of the microsporean, Perezia infecting P. stylifera was found to be very low (1.76%). The spores were found only in the skeletal musculature and the infected shrimp appeared milky white in colour. The spores measured 1.4-2.8 µm x 0.9-1.9 µm. The histological sections revealed extensive lesions that appeared more homogeneous and muscle fibers found to be completely replaced by spores. The spores were stained with different stains viz, Giemsa, Gram's and hematoxylin & eosin (H&E) stain. The Gram's and H&E stained spores at higher magnification often showed a darkly reddish coloured circular body at the one end. Prussian blue stained histological sections showed bluish tinge near the necrotized area of muscle, due to growth of spores. [ABSTRACT FROM AUTHOR]

Interleukin-1 receptor associated kinase-4 (IRAK-4) has been identified as a central signal transduction mediator of the Toll-like receptor (TLR) and Toll/interleukin-1 receptor (TIR) pathways both in vertebrate and invertebrate innate immunity. To investigate the role of Toll-pathway in innate immune response of shrimp, Penaeus monodon, expression analysis of IRAK-4 gene in mid-gut of LPS induced shrimps wasdone at five time points. Responses of this gene to LPS by Quantitative real time PCR (qPCR) expression analysis of the IRAK-4 gene wasdone in control and LPS induced P. monodon. Mid-gut tissue expressions of theIRAK-4 gene was significantly up regulatedin the LPS induced group. The study indicatedthe critical role of IRAK-4 in gut immunityof P. monodon. [ABSTRACT FROM AUTHOR]