First report of Dactylogyrus formosus from India: a case of co-existence with Paradactylogyrus catlaius causing mass mortality in Indian major carp, Catla catla.

The family Dactylogyridae, known for its role as a frequent pathogen in Cyprinids, was identified in a case of mass mortality involving Catla catla fingerlings (measuring 6.5 ± 2.0 cm and weighing 40.5 ± 10 g) in West Bengal, India. Microscopic examination revealed the presence of two co-existing parasites, Dactylogyrus formosus and Paradactylogyrus catlaius, attached to different sections of the gill filament. Despite their coexistence, these parasites exhibited marked differences in their haptoral hard parts, genital organs, and preferred habitats. Molecular analysis of the Internal Transcribed Spacer 1 and 4 genes indicated more than 90% similarity between the detected parasite and D. formosus previously reported in China. Histopathological observations illustrated the parasites' specific attachment to the distal end of the primary gill lamellae, gradually causing destruction to a maximum number of secondary lamellae. Internally, infiltration of eosinophilic granular cells was observed in gill and kidney blood vessels, while the liver exhibited hepatocytes filled with hemosiderin. The infected fish were treated for 24 h with a safe dose of common salt (5.6 ppt) and albendazole (62 ppm). The survivability rate was significantly higher (p < 0.05) in both treated groups compared to the control. Interestingly, the group treated with common salt showed superior results compared to the albendazole-treated fish. This study presents the sympatric speciation of D. formosus in a new host (C. catla) and explores its host specificity, histopathology, and treatment methods. This case marks the first report of D. formosus causing substantial mortality in cultured Catla in India, alongside the coexistence with Paradactylogyrus catlaius.

The ß-actin gene promoter of rohu carp (Labeo rohita) drives reporter gene expressions in transgenic rohu and various cell lines, including spermatogonial stem cells.

We previously characterized the ß-actin gene promoter of Indian domesticated rohu carp (Labeo rohita) and made a reporter construct via fusion to green fluorescence protein (GFP) cDNA. In this study, the same construct was used to breed transgenic rohu fish. About 20% of the transgenic offspring showed ubiquitous expression of the reporter GFP gene. In a few of the transgenic fish, we documented massive epithelial and/or muscular expression with visible green color under normal light. The expression of GFP mRNA was higher in the muscle tissue of transgenic fish than in that of non-transgenic fish. A highly efficient nucleofection protocol was optimized to transfect proliferating spermatogonial cells of rohu using this reporter construct. The ß-actin promoter also drove expressions in HEK293 (derived from human embryonic kidney cells), K562 (human leukemic cells) and SF21 (insect ovarian cells) lines. These findings imply conserved regulatory mechanisms of ß-actin gene expression across eukaryotes. Furthermore, the isolated ß-actin promoter with consensus regulatory elements has the potential to be used in generating transgenic carp with genes of interest and in basic biology research.

Genetic diversity and genome-scale population structure of wild Indian major carp, Labeo catla (Hamilton, 1822), revealed by genotyping-by-sequencing.

Labeo catla (catla) is the second most commercially important and widely cultured Indian major carp (IMC). It is indigenous to the Indo-Gangetic riverine system of India and the rivers of Bangladesh, Nepal, Myanmar, and Pakistan. Despite the availability of substantial genomic resources in this important species, detailed information on the genome-scale population structure using SNP markers is yet to be reported. In the present study, the identification of genome-wide single nucleotide polymorphisms (SNPs) and population genomics of catla was undertaken by re-sequencing six catla populations of riverine origin from distinct geographical regions. DNA isolated from 100 samples was used to perform genotyping-by-sequencing (GBS). A published catla genome with 95% genome coverage was used as the reference for mapping reads using BWA software. From a total of 472 million paired-end (150 × 2 bp) raw reads generated in this study, we identified 10,485 high-quality polymorphic SNPs using the STACKS pipeline. Expected heterozygosity (He) across the populations ranged from 0.162 to 0.20, whereas observed heterozygosity (Ho) ranged between 0.053 and 0.06. The nucleotide diversity (π) was the lowest (0.168) in the Ganga population. The within-population variation was found to be higher (95.32%) than the among-population (4.68%) variation. However, genetic differentiation was observed to be low to moderate, with Fst values ranging from 0.020 to 0.084, and the highest between Brahmani and Krishna populations. Bayesian and multivariate techniques were used to further evaluate the population structure and supposed ancestry in the studied populations using the structure and discriminant analysis of principal components (DAPC), respectively. Both analyses revealed the existence of two separate genomic clusters. The maximum number of private alleles was observed in the Ganga population. The findings of this study will contribute to a deeper understanding of the population structure and genetic diversity of wild populations of catla for future research in fish population genomics.

Establishment of base population for selective breeding of catla (Catla catla) depending on phenotypic and microsatellite marker information.

The phenotypic and microsatellite marker information of nine strains of catla (Catla catla) for growth trait was used to infer relationship within and between strains. This information helped in optimizing the proportion of individuals to be used from each strain while creating a base population for selective breeding. For this purpose, nine strains were collected from different sources and places of India namely West Bengal, Bihar, Odisha, Andhra Pradesh and Uttar Pradesh. Two riverine sources i.e. Ganga and Subarnarekha were also represented among the nine strains collected for base population. They were brought to Indian Council of Agricultural Research-Central Institute of Freshwater Aquaculture (ICAR-CIFA) at fry stage and reared separately till fingerlings. After passive integrated transponder tagging fingerlings were stocked in three communal ponds for one year culture. Live body weights were then measured and least square means were obtained after pond effect correction. A wide range of variation was observed among and between strains. Microsatellite markers were used to estimate genetic differences of different strains of catla using pair wise F ST estimates. Overall multi locus F ST, including all loci was estimated to be 0.4137 (P < 0.05), indicating genetic heterogeneity among them. Analysis of molecular variance revealed that, 58.63% of variation was due to within individual variation, 3.45% of variation was due to among individuals within strain and 37.92% was due to among strain variations. Both phenotypic as well as microsatellite data will be used to form a base population of catla with individuals from the stock having broad genetic variation for selective breeding programme.

Characterization, molecular docking, dynamics simulation and metadynamics of kisspeptin receptor with kisspeptin.

We report molecular characterization of the kisspeptin receptor (kiss1r), an essential gatekeeper for reproduction and onset of puberty in vertebrates. The full-length cDNA sequence of kiss1r is 1786bp which consist of 5' UTR (untranslated region) 261bp, 3' UTR of 424bp and open reading frame of 1101 encoding a putative protein of 366 amino acids. Basal tissue expression pattern of kiss1r mRNA revealed that it is mainly expressed in the brain and testis. We also report the structure of the kiss1r, along with plausible activation mechanism of this receptor by kisspeptin using computational modelling and dynamic simulation approach of multiple 100ns of timescale. A present modelling and simulations studies shed light on the molecular level of interaction, suggesting that direct hydrogen bonds between ASN4, SER5, GLY7, ARG9 and PHE10 of kisspeptin and TRP7, ASN8, GLU11, ILE17, ASN19 and TYR183 of kiss1r could be crucial role players in initial binding of receptor and the kisspeptin towards allosteric modulatory effects of kisspeptin on the receptor. To the best our knowledge, this is the first report on computational modelling and molecular dynamic simulations of kiss1r in animals shedding light on its possible mode of activation.