Iron mediated hematological, oxidative and histological alterations in freshwater fish Labeo rohita.

Iron is an essential element for many physiological functions of several organisms but in excess it causes toxicity. High iron content in water bodies of mountainous states is considered as one of the major factor, responsible for low productivity in aquaculture systems. But, till date comprehensive reports on the adverse effect of iron overload in aquatic organisms, especially cultured fishes are scanty. Therefore, the present study was undertaken to investigate the adverse effects of iron overload in economically important aquaculture fish species Labeo rohita. Three sub-lethal test concentration of iron (ferrous) viz., 1/16th, 1/8th and 1/4th of LC50 (post 96 h) i.e. 8.25, 16.51 and 33.01 mg L-1, respectively, were used for in vivo exposure. Blood cells and tissue samples of the control & exposed specimens were sampled at intervals of 24, 48, 72 and 96 h to assess alterations in hematological, oxidative stress and histological parameters. Significant changes in erythrocyte and leukocyte counts, hemoglobin, lipid peroxidation, antioxidant enzyme activity (super oxide dismutase and catalase) and tissue iron accumulation were observed in the exposed fish. Significant increase in lipid peroxidation, coupled with significant reduction in free radicals scavengers like super oxide dismutase and catalase revealed a compromised anti-oxidative defense mechanism in the fishes exposed to iron overload. Histological examination of gills and liver showed severe tissue injury and histological alternations. Severity was found to increase in time and concentration dependent manner. Perl's staining revealed accumulation of excess iron in liver of the exposed fish. The observed patho-physiological changes in the present study provide the most comprehensive insight of iron overload stress in L. rohita.

DNA Barcoding of Freshwater Fishes of Indo-Myanmar Biodiversity Hotspot.

To develop an effective conservation and management strategy, it is required to assess the biodiversity status of an ecosystem, especially when we deal with Indo-Myanmar biodiversity hotspot. Importance of this reaches to an entirely different level as the hotspot represents the area of high endemism which is under continuous threat. Therefore, the need of the present study was conceptualized, dealing with molecular assessment of the fish fauna of Indo-Myanmar region, which covers the Indian states namely, Manipur, Meghalaya, Mizoram, and Nagaland. A total of 363 specimens, representing 109 species were collected and barcoded from the different rivers and their tributaries of the region. The analyses performed in the present study, i.e. Kimura 2-Parameter genetic divergence, Neighbor-Joining, Automated Barcode Gap Discovery and Bayesian Poisson Tree Processes suggest that DNA barcoding is an efficient and reliable tool for species identification. Most of the species were clearly delineated. However, presence of intra-specific and inter-specific genetic distance overlap in few species, revealed the existence of putative cryptic species. A reliable DNA barcode reference library, established in our study provides an adequate knowledge base to the groups of non-taxonomists, researchers, biodiversity managers and policy makers in sketching effective conservation measures for this ecosystem.

DNA barcoding and genetic diversity analyses of fishes of Kaladan River of Indo-Myanmar biodiversity hotspot.

Species are considered as a fundamental unit of biodiversity. Therefore, the prerequisite for biodiversity management and conservation is to know the number of species one is dealing with. Consequently, the need of the present study was conceptualized, which dealt with the comprehensive molecular appraisal of Kaladan's Fish fauna. A total of 291 specimens representing 49 species, 28 genera, 11 families, and 4 orders, were collected from 11 sampling stations situated along the main Kaladan River and its four major tributaries, i.e. Tiau, Tuipui, Mat, and Tuichang, flowing in Mizoram state of India (part of Indo-Myanmar biodiversity hotspot) and COI sequences of all the 291 samples were generated. All the analyses conducted in the present study, i.e. K2P genetic divergence, bPTP and Neighbour-Joining suggest that DNA Barcoding is an efficient and reliable tool for species identification and deciding the species boundary. Most of the species of Kaladan showed the clear existence of barcode gap. However, the presence of intra-specific and inter-specific genetic distance overlap in two species revealed the existence of putative sibling species or hidden taxa. This study also revealed the presence of two cryptic species and putative previously unknown species of genus Garra and Schistura. The COI barcode database of Kaladan's fish fauna, established in the present study, may serve as a reference library for accurate identification of fishes and will help ichthyologist, researcher, students, biodiversity managers and policy makers in proper planning with regard to conservation and management of the resources.

Complete mitochondrial genome of near threatened fish species Osteobrama belangeri (Cypriniformes: Cyprinidae).

The complete mitochondrial genome of Osteobrama belangeri was obtained, using Illumina high-throughput NextSeq 500 with 2 × 150 bp sequencing of mitochondrial DNA. The mitochondrial genome of O. belangeri was 16,602 bp in length (GenBank Accession No. KY887473), comprised of 13 protein coding genes, 22 tRNA genes, 2 rRNA genes and a control region, i.e. D-loop. In present mitogenome, 11 short sequence repeats were identified and validated in silico. The arrangement of genes was found identical to other Cypriniformes fish mitogenomes, available in NCBI database. Phylogenetic relationship established in the present study also supported that genus Osteobrama is member of subfamily Cyprininae (tribe: smiliogastrini) not Cultrinae, which provide useful insights into taxonomic status of the genus.

Complete mitochondrial genome of near threatened butter Catfish Ompok bimaculatus (Siluriformes: Siluridae).

The complete mitochondrial genome of Ompok bimaculatus was obtained, using illumina high-throughput NextSeq 500 with 2 × 150 bp sequencing of mitochondrial DNA. The genome of O. bimaculatus was 16,482 bp in length (GenBank Accession No. KY887474) comprised of 13 protein-coding genes, 22 tRNA genes, 2 rRNA genes and a control region i.e. D-loop. In present mitogenome, 9 SSR were identified and validated in silico and secondary structures of all the 22 tRNA were predicted. The arrangement of genes was found identical to other siluriformes fish mitogenomes available in NCBI database. Phylogenetic relationship with closely related species were established which provide useful insights into taxonomic status of the species.

Evidence of birth-and-death evolution of 5S rRNA gene in Channa species (Teleostei, Perciformes).

In higher eukaryotes, minor rDNA family codes for 5S rRNA that is arranged in tandem arrays and comprises of a highly conserved 120 bp long coding sequence with a variable non-transcribed spacer (NTS). Initially the 5S rDNA repeats are considered to be evolved by the process of concerted evolution. But some recent reports, including teleost fishes suggested that evolution of 5S rDNA repeat does not fit into the concerted evolution model and evolution of 5S rDNA family may be explained by a birth-and-death evolution model. In order to study the mode of evolution of 5S rDNA repeats in Perciformes fish species, nucleotide sequence and molecular organization of five species of genus Channa were analyzed in the present study. Molecular analyses revealed several variants of 5S rDNA repeats (four types of NTS) and networks created by a neighbor net algorithm for each type of sequences (I, II, III and IV) did not show a clear clustering in species specific manner. The stable secondary structure is predicted and upstream and downstream conserved regulatory elements were characterized. Sequence analyses also shown the presence of two putative pseudogenes in Channa marulius. Present study supported that 5S rDNA repeats in genus Channa were evolved under the process of birth-and-death.

Chromosome breakages associated with 45S ribosomal DNA sequences in spotted snakehead fish Channa punctatus.

It is well known that transcriptionally inactive rRNA genes are correlated with DNA hyper-methylation and histone hypo-methylation and there is clear evidence in humans that DNA and histone modification which alter chromatin structure are related to chromosome fragility. Very little is known about the biological cause of 45S rDNA fragility. In this report we characterized the chromosome breakage or gap associated with 45S rDNA in a fish species Channa punctatus. The rDNA mapping in C. punctatus, showed many chromosome breakages or gap formations, and all occurred exclusively in the 45S rDNA sites in anterior kidney cells. We observed that the number of chromosomes plus chromosome fragments was often more than the expected 32 in most cells. Total 67 % metaphase spread showed the expected or normal 32 chromosomes, while 33 % metaphase spread showed 33 and/or 34 chromosomes and/or chromosome fragments. The chromosome lesions observed in this study are very similar cytologically to that of fragile sites observed in human chromosomes. Possible causes for the spontaneous expression of fragile sites and their potential biological significance are also discussed in present report.