Sumanta Kumar Mallik

Molecular cloning, characterization and expression profile of kisspeptin1 and kisspeptin1 receptor at brain-pituitary-gonad (BPG) axis of golden mahseer, Tor putitora (Hamilton, 1822) during gonadal development

Complete cDNA sequences of kiss1 (gmkiss1) and its receptor kiss1r (gmkiss1r) were cloned and characterized from brain tissue of adult golden mahseer (Tor putitora). Thereafter, quantification of gmkiss1 and gmkiss1r mRNA expression in brain-pituitary-gonad (BPG) axis of male and female golden mahseer was carried out using quantitative real-time (qRT)-PCR assay during an annual reproductive cycle, at different gonadal development stages. The gmkiss1 cDNA was 508bp, with 330bp open reading frame (ORF), encoding a precursor protein of 109 amino acids, whereas gmkiss1r cDNA was 1383bp with an ORF of 1004bp, which encodes a 334 amino acid protein residue. The qRT-PCR study shows that gmkiss1 and gmkiss1r are expressed in brain, pituitary and gonads of both the sexes of golden mahseer. An apparent sexual dimorphism in transcript level of gmkiss1 and gmkiss1r in brain and gonads was evident during the reproductive cycle. Overall, in brain, testis and ovary, the gmkiss1 and gmkiss1r mRNA expression level was comparatively higher during the initial stages of gonadal development, than that of spermiation or ovulation stage. In pituitary of both the sexes, throughout the gonadal development, consistently low transcript level of gmkiss1 and gmkiss1r was observed. The gmkiss1 mRNA expression level in brain and ovary of female golden mahseer was several folds higher than the brain and testis of male fish. In conclusion, we confirm the presence of kiss1 and its receptor in golden mahseer, and results of our study strongly suggested the involvement of kisspeptin1 system in gonadal development and annual reproductive cycle of this species.

The microcystins-induced DNA damage in the liver and the heart of zebrafish, Danio rerio

Microcystins (MCYST) are the freshwater cyanobacterial toxins, known to induce hepatocellular carcinoma, necrosis, intrahepatic bleeding, as well as human and livestock mortality. Within hepatocytes, MCYST selectively bind to protein phosphatases 1 and 2A, resulting in severe liver damage. The toxicology of MCYST in mice and rats has been well studied, but little is known regarding genotoxicity in aquatic animals. In this study, the zebrafish, Danio rerio was exposed to crude extract of Microcystis aeruginosa bloom. Liver and heart were examined for MCYST-induced toxicity. Light microscopy at 36 h revealed severe, widespread apoptotic necrosis of the majority of hepatocytes, and cytoskeletal deformation in myocardiocytes. Hepatocytes were dissociated with cell shrinkage and margination of nuclear chromatin. Laddering of genomic DNA from the liver and heart of the exposed fish in an increment of 180–200 bp was consistent with apoptosis. Fluorimetric analysis of DNA unwinding was carried out to determine the DNA strand breakage. After 36 h exposure, the % double-stranded DNA was significantly reduced in hepatocytes and myocardiocytes. In conclusion, the results obtained in this study indicate that, the extract of M. aeruginosa bloom is genotoxic to fish. The DNA damage observed in this study may be attributed to the activation of DNA endonucleases. This model of DNA damage may contribute for identifying novel molecular mechanisms of interest for therapeutic application.

Gonadal Development Stages of Wild Male Golden Mahseer, Tor putitora from Nainital Region of Uttarakhand, India

Golden mahseer, Tor putitora is an endangered fish of mid-Himalayan regions of India. It has good potential as aquaculture species for hill aquaculture, due to its high market demand. But the major constrains on introduction of this fish for aquaculture is its inability to breed in captivity and slow growth rate. Therefore, studies were carried out on its breeding biology to captive breed this fish for sustainable seed production. However, detailed study on reproductive pattern of adult golden mahseer is very limited. Therefore, in the present study, we have developed a macroscopic grading system for golden mahseer testes, which shows the testes development stages during the breeding season, which lasts from May-September in Bhimtal and Sattal lakes. The golden mahseer were sampled from February - September 2014, from Bhimtal and Sattal lakes. Altogether, 48 samples were collected during the sampling period. Based on macroscopic observation, the maturation stage of the testes was divided into five developmental stages: Immature (I), early spermatogenic (II), late spermatogenic (III), matured (IV) and spent (V).

Occurrence of Ichthyophthirius multifiliis (White spot) infection in snow trout, Schizothorax richardsonii (Gray) and its treatment trial in control condition

High altitude raceways reared Schizothorax richardsonii stocks were monitored periodically for white spot infection at experimental coldwater fish farm, Chhirapani, Champawat, Uttarakhand. Total 1268 numbers of fishes with mean length (cm) ranging from 15.53 ± 0.20 to 16.86 ± 0.08, and mean weight (g) 24.70 ± 0.05 to 26.73 ± 0.06 were examined from January - December 2009. Presence of pinhead sized white spots (0.4 to 0.8 mm) was observed on dorsal body surface and caudal fins of sampled fishes during month of April. The causative agent was identified to be a ciliate parasite, Ichthyophthirius multifiliis. A temperature dependant infection pattern was noted with maximum prevalence (%) of 84.80 ± 1.83 in July followed by a decline in December (21.99 ± 2.13). Prevalence varied significantly (p< 0.05) between the months as water temperatures dropped with onset of winter. Trophont counts following dip treatment for five consecutive days under laboratory conditions with 2% common salt, 250 ppm formalin and a combination of the two, of samples of the snow trout, Schizothorax richardsonii, infected with Ichthyophthirius multifiliis, indicated that treatment with combination of salt and formalin was significantly (p< 0.05) effective than either salt or formalin alone in controlling the infection.