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Background. The investigation on different aspects of the reproductive biology is valuable information in the development of breeding technologies towards initiating conservation and other management measures of the indigenous fish stocks. The zig-zag eel, Mastacembelus armatus (Lacepède, 1800), is a commercially important fish species in the river Ganga of India. But, the data on the reproductive biology of this species is limited. Hence, this study was done to gather information on some aspects of the reproductive biology of M. armatus to address the gap in the current knowledge. Materials and methods. Some biological traits relating to the reproduction of M. armatus from the river Ganga were studied based on the monthly sampling for one year from April 2015 to March 2016. A total of 286 fish specimens were collected, comprising 167 males and 119 females. Weight-length relations for both sexes were estimated with the aid of regression analysis. The fecundity was calculated following the gravimetric method. The length at 50% maturity (L50) for the male and female were assessed employing maturity status data. The spawning season was predicted by employing gonadosomatic index and maturity status data. Results. Monthly sex ratio (F ÷ M) ranging between 0.22 ÷ 1 and 2.75 ÷ 1 with a mean of 0.71 ÷ 1 observed in the population was significantly different from 1 ÷ 1. Analysis of mean monthly gonadosomatic index (GSI) and the existence of matured (IV and V) and spent (VI) individuals, indicated year-round spawning with two breeding seasons. The first breeding season, in the river Ganga, occurred between February and May, and the other between July and November. The L50 of Mastacembelus armatus female and male were determined as 362.2 and 385.6 mm total length (TL), respectively. The reproductive potential in terms of absolute fecundity ranged between 2546 and 6058 with a mean of 3962 ova. Conclusion. The current investigation helps to report the size at maturity in the female and the male for the first time from Indian waters. Mastacembelus armatus represents a low fecundity, indicating that this species has a comparatively lower reproductive potential, making it more vulnerable to excessive fishing pressure. For the sustainable management of this species, it is necessary to utilize the resources wisely and avoid overfishing in the river Ganga. [ABSTRACT FROM AUTHOR]

The aim of this study was to determine the ontogeny of antiviral Mx gene expression in different stages of development of Cirrhinus mrigala (mrigal). For this purpose, three experiments were designed; in the first experiment, Mx expression was observed in eggs, milt, poly I:C treated twitching stage and control twitching stage, and the Mx expression was maximum in eggs. In the second experiment, upregulation of Mx transcript was studied in hatchling stages of mrigal after poly I:C induction by bath treatment, while control hatchlings were studied as such. Hatchlings (both control and treated) were collected at 2-, 4-, 6- and 8-h interval after 24, 48, 72 and 96 h of poly I:C induction. The Mx gene expression showed an increasing trend up to 72 h, where it was highest 3.3-fold higher than the control and then decreased at 96 h where it was threefold higher when compared to the control. In the third experiment, expression of Mx transcript was studied in mrigal fry after intramuscular stimulation with poly I:C for a duration of 28 days. A gradual upregulation of Mx transcript was seen for the experimental period of 28 days. From the study, it is concluded that Mx gene is transmitted from egg and twitching stages and reduced in larvae and fry. Hence, ontogenically, without poly I:C induction, Mx gene is constitutively expressed at early stages indicating the antiviral defences transmitted from parents to offspring in the process of embryonic development. This indicates there is an antiviral Mx defence mechanism playing at early stages of the development for a period of 45 days. [ABSTRACT FROM AUTHOR]

The length–weight relationships (LWRs) of three freshwater fish species from the Kangsabati and Rupnaryan river in West Bengal, India are presented, namely as Amblypharyngodon microlepis (Bleeker, 1853), Parambassis lala (Hamilton, 1822) and Macrognathus aculeatus (Bloch, 1786). Gill‐nets (mesh sizes with 0.5 cm–4 cm), cast‐nets (up to 1 × 1 cm mesh size with up to 4.0 m2 area) and scoop‐nets (0.3 × 0.3 cm and 0.5 × 0.5 cm mesh size) were used from January, 2017 to April, 2018. Sampling was done every 15 days during this period. The value of parameter "b" ranged from 2.751 to 2.895 with highly significant correlations (r2 > 0.95). [ABSTRACT FROM AUTHOR]

We fabricated ZnS nanocrystals decorated single-walled carbon nanotube (SWNT) based chemiresistive sensor for DNA. Since the charge transfer in the hybrid nanostructures is considered to be responsible for many of their unique properties, the role of ZnS nanocrystals toward its performance in DNA sensor was delineated. It was found that the free carboxyl groups surrounding the ZnS nanocrystals allowed large loading of single strand DNA (ssDNA) probe that provided an ease of hybridization with target complementary c-ssDNA resulting in large electron transfer to SWNT. Thus it provided a significant improvement in sensitivity toward c-ssDNA as compared to bare SWNT based DNA sensor. [ABSTRACT FROM AUTHOR]