Population Genetic Structure of Endemic and Endangered Yellow Catfish, Horabagrus brachysoma, Using Allozyme Markers

The allozyme variation and population genetic structure of Horabagrus brachysoma in three natural populations from the southern part of theWestern Ghats region, India, were investigated by polyacrylamide gel electrophoresis. Variations at 14 loci from 14 enzyme systems were analyzed. The allozyme analysis revealed a high level of genetic variation in this species, with an average of observed alleles per locus of 2.357 and observed heterozygosity of 0.178. The positive value of the fixation index (FIS = 0.507) implied a significant deficiency of heterozygosity at the population level. The highly significant probability (P<0.0001) for the overall loci suggested that the three sample sets were not part of the same gene pool

Identification of female specific protein in seabass, Lates calcarifer (Bloch)

Electrophoretic serum protein profile of female Lates calcarifer reveals appearance of female specific protein during gonadotropic dependent stages of ovarian growth. The protein is conspicuously absent in the serum of maturing males. The protein stains positively for carbohydrate, lipids and calcium indicating it to be vitellogenin. The vitellogenin band first appears in fish with maturing ovaries (stage 3) and stain intense and sharp till stage 4. At stage 5 (ripe) the band appears diffused. The protein is lacking in the serum profile of immature (stage 1), resting preparatory (stage 2) and spent (stage 6) as well as in maturing male fish. The correlative pattern of vitellogenin band with ovarian maturation stages provides evidence of single spawning in L. calcarifer

Identification of polymorphic allozyme markers for population structure analysis in Horabagrus brachysoma (Gunther, 1864).

Fourteen polymorphic allozyme loci were identified in yellow catfish, Horabagrus brachysoma. The genetic variation detected at each allozyme locus was assessed for samples collected from three rivers. The observed heterozygosities per locus ranged from 0.0286 to 0.4000. Significant genotype heterogeneity indicated that the samples are not drawn from same gene pool. The results suggest the potential of the identified loci to analyze stock structure of natural populations of H. brachysoma

A molecular approach to reveal the genetic identity of parrot mussel and other sympatric mussel species distributed along the Kerala coast

Two commercially important mussel species are recorded from the Indian coast: green mussel Perna viridis (Linnaeus, 1758) and brown mussel P. indica (Kuriakose and Nair, 1976). Apart from this, a third type referred to as parrot mussel, which has shell shape of brown mussel, but with green shell colouration and suspected to be the hybrid of the above two species has also been reported from Kollam coast of Kerala, where both the species co-occur. In the present work, genetic identity of parrot and sympatric mussel species was determined using protein and genomic DNA markers. Protein markers viz. Sodium Dodecyl Sulphate Polyacrylamide Gel Electrophoresis (SDS-PAGE) and allozymes and the genomic DNA marker Random Amplified Polymorphic DNA (RAPD) were used for determining genetic identity of the three mussel groups. The green and brown mussels could be clearly differentiated using SDS PAGE. The parrot mussel protein pattern was similar to that of brown mussel, except for an additional band of molecular weight 48.7 Kda which is unique to brown mussel. Genus specific protein bands for Perna viz. 66 Kda, 43 Kda and 14.3 Kda, were detected in this study. Allozyme electrophoresis also followed a similar pattern. Of the 10 allozyme loci studied, seven revealed speciesspecific diagnostic differences between P.viridis and P.indica. They were AAT-1* (Aspartate Amino Transferase-1*), AAT-2*, ME (Malic Enzyme)*, PGM-2*(Phospo Gluco Mutase-2*), EST-1* (Esterase- 1*), EST-2*, IcDH* (Isocitrate Dehydrogenase)*. Parrot mussel shared all the alleles of brown mussel, and no hybrid pattern was observed. Species-specific alleles clearly differentiated green mussel from both brown and parrot mussel. The genetic distance of green mussel from brown mussel, estimated from allozyme data was 1.1145 and with parrot mussel it was 1.105. The genetic distance between parrot mussel and brown mussel was negligibly low (0.0005). Using allozyme and RAPD data, the Nei’s Unbiased Measures of genetic distance were calculated and the dendograms prepared based on these values clearly depicted the separation of parrot mussel from green mussel as well as the close resemblance of parrot mussel with brown mussel. The higher gene flow (1.1539) determined using RAPD marker also hints that brown and parrot mussel may be acting as single interbreeding population. Hence this study using molecular tools to test the genetic identity of parrot mussel has helped to conclude that parrot mussel is only a morphotype of brown mussel and not a true hybrid of the two

Effect of extender composition on sperm cryopreservation of Asian catfish Heteropneustes fossilis (Bloch) and Clarias batrachus (Linnaeus)

Air breathing catfish species Heteropneustes fossilis (Bloch) and Clarias batrachus (Linn.) are important table fish and fetch high market price. Cryopreservation of spermatozoa can be a useful tool in captive seed production for domestication and aquaculture of these catfish species. The objective of the present study was to identify optimum extender composition for sperm cryopreservation of the two species, H. fossilis and C. batrachus. Four extender compositions Hank’s Balanced Salt Solution (HBSS), Modified Hank’s Balanced Salt Solution (M-HBSS), Modified Hank’s Balanced Salt Solution with hen’s egg yolk (M-HBSS with EY) and European catfish were evaluated for cryopreservation of catfish sperm and 10 % Dimethyle Sulphoxide (DMSO) was used as a cryoprotectant. The pooled milt exhibiting 70-80% motile sperm was used for cryopreservation experiment. After storage for 48 hrs at -196ºC, the milt was thawed and evaluated for fertility test. The percentage of hatching was used as a parameter for the comparative evaluation of different extender composition. In H. fossilis extender M-HBSS indicated highest hatching rate (49.06%), followed by HBSS (42.76%), M-HBSS with EY (37.46%) and European catfish (29.47%). The hatching success with extender M-HBSS did not differ significantly (P > 0.05) from the control group (51%). In C. batrachus extender HBSS exhibited highest hatching (62.1 %), followed by M-HBSS with EY (51.6%), European Catfish (46.3%) and M-HBSS (40.9%). The hatching rate in control was 90% in C. batrachus. The results indicated that the two species differ in the protocol for sperm cryopreservation. The paper presents successful cryopreservation of sperm with the production of viable hatchlings of H. fossilis and C. batrachus for the first time. The protocol reported in the study can be used for scaling up of seed production of these two catfish species

DNA barcoding Indian marine fishes

DNA barcoding has been adopted as a global bio-identification system for animals in recent years. A major national programme on DNA barcoding of fish and marine life was initiated in India by the authors during 2006 and 115 species of marine fish covering Carangids, Clupeids, Scombrids, Groupers, Sciaenids, Silverbellies, Mullids, Polynemids and Silurids representing 79 Genera and 37 Families from the Indian Ocean have been barcoded for the first time using cytochrome c oxidase I gene (COI) of the mtDNA. The species were represented by multiple specimens and a total of 397 sequences were generated. After amplification and sequencing of 707 base pair fragment of COI, primers were trimmed which invariably generated a 655 base pair barcode sequence. The average Kimura two parameter (K2P) distances within species, genera, families, orders were 0.30%, 6.60%, 9.91%, 16.00%, respectively. In addition to barcode-based species identification system, phylogenetic relationships among the species have also been attempted. The neighbour-joining tree revealed distinct clusters in concurrence with the taxonomic status of the species

Transcriptome analysis reveals immune pathways underlying resistance in the common carp Cyprinus carpio against the oomycete Aphanomyces invadans

Infection with Aphanomyces invadans is a serious fish disease with major global impacts. Despite affecting over 160 fish species, some of the species like the common carp Cyprinus carpio are resistant to A. invadans infection. In the present study, we investigated the transcriptomes of head kidney of common carp experimentally infected with A. invadans. In time course analysis, 5288 genes were found to be differentially expressed (DEGs), of which 731 were involved in 21 immune pathways. The analysis of immune-related DEGs suggested that efficient processing and presentation of A. invadans antigens, enhanced phagocytosis, recognition of pathogen-associated molecular patterns, and increased recruitment of leukocytes to the sites of infection contribute to resistance of common carp against A. invadans. Herein, we provide a systematic understanding of the disease resistance mechanisms in common carp at molecular level as a valuable resource for developing disease management strategies for this devastating fish-pathogenic oomycete

Low Genetic Differentiation in the Populations of the Malabar Carp Labeo dussumieri as revealed by Allozymes, Microsatellites and RAPD

The population structure of Labeo dussumieri, an endangered and endemic cyprinid from three riverine locations in the Western Ghats, India was investigated using allozyme, microsatellite and RAPD markers. L. dussumieri samples were obtained from Meenachil, Manimala and Pamba River basins, Kerala. Fourteen (46.7%) out of 30 allozyme loci, seven microsatellite loci and 12 RAPD Operon decamers gave polymorphic pattern. Six allozyme loci (AAT-2*, EST-4*, GLDH*, GPI-2*, G6PDH* and LDH-2*) and three microsatellite loci (LdussG1, MFW19 and Bgon22) exhibited consistent significant deviation from Hardy-Weinberg Equilibrium expectations in different populations after probability level (P<0.05) was adjusted for sequential Bonferroni correction. All the three marker types demonstrated concordant results and various estimates revealed genetic variability within the subpopulations but surprisingly low level (= 0.0034 to 0.0081) of genetic differentiation among L. dussumieri from different river samples. AMOVA analysis also indicated low differentiation among subpopulations. No evidence for a recent genetic bottleneck was observed in L. dussumieri populations based on allozyme and microsatellite data set analysis. Meenachil, Manimala and Pamba Rivers open in to the southern end of Vembanad Lake in Kerala and are connected to each other in the lower reaches through an extensive network of natural canals. Common ancestry in the prehistoric period; and possible mixing of fish populations resulting in high gene flow across the rivers through the lake and interconnecting canals could have been responsible for the lack of significant allelic heterogeneity among the L. dussumieri populations. The stocks from the three rivers do not require different management strategies and for propagation assisted river ranching programme of this species, large effective breeding population can be developed by mixing individuals from three river

Derivation and Characterization of a ES-Like Cell Line from Indian Catfish Heteropneustes fossilis

A cell line designated as HFB-ES was established from blastula stage embryos of H. fossilis (Singhi). The embryonic cells were harvested and maintained in Leibovitz’s medium supplemented with 15% fetal bovine serum. The cell line had been subcultured for more than 90 passages in a period of 24 months. HFB-ES cells were able to grow at temperatures between 25 and 35°C with an optimum temperature of 28°C. The growth rate of HFB-ES was proportional to FBS concentration, with optimum growth seen at 15% FBS concentration. The originality of the cell line was confirmed by sequencing of cytochrome oxidase c subunit I (COI), cytochrome b gene, and microsatellite DNA profile. Results of chromosome complements of HFB showed normal karyo-morphology with 56 (2n) diploid number of chromosomes after 40 passages which indicated that the developed cell line is chromosomally stable. The pluripotency of HFB was demonstrated by alkaline phosphatase activity and Oct-4 gene expression. Expression of GFP reporter gene was successful in HFB-ES. These results indicated that HFB-ES could be utilized for future gene expression studies

Molecular insights into the mechanisms of susceptibility of Labeo rohita against oomycete Aphanomyces invadans

Aphanomyces invadans, the causative agent of epizootic ulcerative syndrome, is one of the most destructive pathogens of freshwater fishes. To date, the disease has been reported from over 160 fish species in 20 countries and notably, this is the first non-salmonid disease that has resulted in major impacts globally. In particular, Indian major carps (IMCs) are highly susceptible to this disease. To increase our knowledge particularly with regards to host immune response against A. invadans infection in a susceptible host, the gene expression profile in head kidney of A. invadans-infected and control rohu, Labeo rohita was investigated using RNA sequencing. Time course analysis of RNA-Seq data revealed 5608 differentially expressed genes, involved among others in Antigen processing and presentation, Leukocyte transendothelial migration, IL-17 signaling, Chemokine signaling, C-type lectin receptor signaling and Toll-like receptor signaling pathways. In the affected pathways, a number of immune genes were found to be downregulated, suggesting an immune evasion strategy of A. invadans in establishing the infection. The information generated in this study offers first systematic mechanistic understanding of the host-pathogen interaction that might underpin the development of new management strategies for this economically devastating fish-pathogenic oomycete A. invadans